Abstract

Gulf War veterans have reported health problems that they attribute to their military service, but little is understood about the nature or extent of these conditions. To determine whether Kansas Gulf War veterans are affected by excess health problems, a population-based survey of 1,548 veterans who served in the Persian Gulf War (PGW) and 482 veterans who served elsewhere (non-PGW) was conducted in 1998. Gulf War illness, defined as having chronic symptoms in three of six domains, occurred in 34% of PGW veterans, 12% of non-PGW veterans who reported receiving vaccines during the war, and 4% of non-PGW veterans who did not receive vaccines. The prevalence of Gulf War illness was lowest among PGW veterans who served on board ship (21%) and highest among those who were in Iraq and/or Kuwait (42%). Among PGW veterans who served away from battlefield areas, Gulf War illness was least prevalent among those who departed the region prior to the war (9%) and most prevalent among those who departed in June or July of 1991 (41%). Observed patterns suggest that excess morbidity among Gulf War veterans is associated with characteristics of their wartime service, and that vaccines used during the war may be a contributing factor. Am J Epidemiol 2000;152:992–1002.

On August 2, 1990, Iraq's Republican Army invaded Kuwait. Within 1 week, US military forces began to arrive in the region as part of Operation Desert Shield. Operation Desert Storm began with the air war on January 17, 1991, and continued with a 4-day ground war that ended February 28, 1991. After the war, the force size was reduced over a period of months, with the majority of troops out of the area by July 1991 (1). Since the war, Gulf War veterans have reported anomalous health problems that include a variety of chronic symptoms such as headache, fatigue, joint pain, rashes, respiratory problems, and neuropsychological difficulties.

Despite a growing body of research on the health problems reported by Gulf War veterans, little is known about their nature or causes. Government review panels (24) have generally not found that a single “Gulf War syndrome” is likely to explain all of the health problems reported by veterans. At the same time, research studies have consistently documented similar types of symptoms and illnesses in different groups of Gulf War veterans (59) and have invariably found these problems to occur at higher rates in Gulf War veterans than in veterans serving elsewhere (1015).

Basic epidemiologic questions regarding the prevalence of these conditions and their association with characteristics of Gulf War service have also remained unanswered. The lack of progress in identifying these parameters is due in part to the difficulty of investigating symptom-based health problems that lack corresponding clinical signs and for which no accepted case definition exists (1, 5, 8, 16, 17). By December 1997, about 12 percent of eligible veterans who had served in the Persian Gulf War (PGW) had enrolled in one of two voluntary registries offered by the US Departments of Defense and Veterans Affairs (18). Population-based studies, however, have suggested that a substantially higher proportion of veterans are experiencing health problems (1315).

The Kansas Persian Gulf War Veterans Health Initiative Program was developed by the state of Kansas in response to veterans' claims that they had health problems resulting from Gulf War service. The present study was designed to determine if Kansas Gulf War veterans experienced a greater burden of health problems than contemporary veterans who did not serve in the Gulf War and, if so, to describe any excess health problems, their prevalence, and patterns of occurrence.

MATERIALS AND METHODS

Study design and population

Veterans were eligible for the study if they 1) were Kansas residents at the time of the study, 2) had served on active military duty for any period between August 1990 and July 1991, and 3) were separated or retired from the military or currently served in the reserve component. The Defense Manpower Data Center provided names, deployment, and demographic information for individuals who had served on active duty during the target year, whose last address of record was in Kansas. Based on earlier reports that reservists and women were disproportionately affected by post-Gulf War health problems (5, 13, 14), a stratified random sample was drawn to increase representation of those two groups. A sample of 3,138 names, including all activated reservists from the pool of eligible names and a similar number of active component veterans, was selected to be located, screened, and invited to participate. Because the military does not maintain current addresses after veterans have been discharged from service, contact information was identified using state records, telephone directories, Internet listings, and postal service files. Contact attempts were limited to veterans for whom in-state information was identified.

Data collection

Interviews were conducted by telephone between February and August of 1998, using a computer-assisted telephone interviewing system. The survey instrument was designed to provide health information, particularly symptom data, comparable with that from other studies of Gulf War veterans. Questionnaires from previous population-based studies were reviewed. A list of representative health questions was generated and pretested in a group of Missouri Gulf War veterans. Veterans were asked if they had ever been diagnosed or treated by a physician for any of 16 specific medical and psychiatric conditions, or for any medical condition in five general areas, and when each reported condition had developed. Veterans were also asked if 37 individual symptoms had been persistent or recurring problems in the prior year, to rate the severity of each symptom endorsed, and when the problem first began. Only limited questions were asked about veterans' military service. Deployed veterans were asked when they arrived in and departed from the Persian Gulf area, the countries to which they deployed, the units with which they served, and whether they had been notified by the Department of Defense that they had been in the area potentially affected by the Khamisiyah munitions demolition in Iraq. Veterans who did not serve in the Persian Gulf War (non-PGW) were asked if they had received any vaccinations or injections from the military between August 1990 and July 1991.

Criteria for “Gulf War illness” symptom complex

The approach used to characterize the health problems reported by Kansas Gulf War veterans relied on two basic premises. First, not all symptoms and conditions experienced by Gulf War veterans were likely to be attributable to their wartime service. Some level of symptomatology and disease would be expected among Gulf War veterans even had they not served in the war (19, 20). Second, the level of morbidity expected in the absence of Gulf War service could be estimated from an appropriate referent group. Any identified excess or atypical morbidity associated with PGW deployment might then be considered “Gulf War illness.” Lacking a gold standard for Gulf War illness, cases were defined by a method similar to that used for another condition defined primarily by symptoms, chronic fatigue syndrome (21). It involved identification of “exclusionary” conditions—that is, medical and psychiatric diagnoses not included under the general category of “Gulf War illness” for current research purposes—and quantifying the symptoms reported by PGW veterans to define “inclusionary” criteria.

Exclusionary conditions.

Diagnosed medical and psychiatric conditions were not included under the general rubric of Gulf War illness if they: 1) were not elevated among Kansas PGW veterans but might produce symptoms similar to those previously associated with Gulf War service, or 2) might interfere with respondents' perception or reports of their symptoms (i.e., serious psychiatric conditions). Therefore, veterans who reported being diagnosed or treated by a physician for any of the following conditions were excluded from consideration as Gulf War illness cases: cancer, diabetes, heart disease, chronic infectious disease, problems resulting from postwar injuries, liver disease, lupus, multiple sclerosis, stroke, or any serious psychiatric condition (those associated with psychosis and/or for which the respondent had been hospitalized since 1991).

Symptom groups and criteria.

Several approaches to quantifying symptom criteria were considered, including exploratory factor analysis to identify latent constructs that might be used to define symptom groupings or illness subtypes. This approach provided general validation regarding the cooccurrence of symptoms within system-based categories (e.g., respiratory symptoms tended to occur together, as did gastrointestinal symptoms, and so on). The cooccurrence of symptoms in different categories, however, varied in veteran subgroups (e.g., PGW vs. non-PGW veterans, males vs. females, PGW veterans deployed to different areas). This method was therefore not considered a reliable way to define illness subtypes in this population. Instead, a more descriptive approach was taken, defining symptom groups based on measures of correlation and comparisons between PGW and non-PGW veterans. Veterans were asked about symptoms in several general categories (e.g., respiratory, gastrointestinal, neuropsychological, sleep disturbances, pain), as well as symptoms (e.g., fatigue, headache) for which no single category was apparent. Gulf War illness criteria symptoms must have persisted or recurred in the year prior to interview and first have been a problem for respondents in 1990 or later. The correlation of symptom scores was assessed among PGW veterans who did not report exclusionary conditions. The internal reliability of each symptom grouping was determined using Cronbach's alpha (22). Symptom groups were considered reliable constructs if they were associated with an alpha of 0.70 or greater; individual items were retained within symptom groups if they had item-scale correlations of 0.50 or greater. Symptoms not included in a group were iteratively correlated with all symptom groups in order to identify additional associations according to the above criteria. In this manner, five highly reliable symptom groups were identified: 1) fatigue/sleep problems (α = 0.81), 2) pain symptoms (α = 0.78), 3) neurologic/cognitive/mood symptoms (α = 0.89), 4) gastrointestinal symptoms (α = 0.77), and 5) respiratory symptoms (α = 0.76). One additional symptom group, skin symptoms, was identified. Veterans were asked specifically about only one skin symptom (rashes), dis-allowing correlation assessments. This symptom was frequently reported, strongly associated with deployment, and relatively independent of other symptom groups. Veterans also frequently reported other skin problems, about which they had not specifically been asked.

A similar proportion of PGW and non-PGW veterans reported a very low level of symptomatology within most symptom groups (e.g., 9 percent of non-PGW veterans reported a single, mild fatigue/sleep problems symptom, compared with 10 percent of PGW veterans). Greater symptom burdens were significantly associated with PGW deployment in all symptom categories. Therefore, only respondents with at least one moderately severe symptom or two or more symptoms within a group were considered to have an elevated level of symptoms in that group.

Criteria for other symptom-defined outcomes.

Cases of multisymptom illness as defined by the Centers for Disease Control and Prevention were required to have one or more chronic symptoms from at least two of the following three groups: 1) fatigue; 2) mood/cognition (feeling down or depressed, memory problems, difficulty concentrating, trouble finding words, problems falling or staying asleep); and 3) musculoskeletal (joint pain, muscle pain) (14). Cases of chronic fatigue syndrome were defined on the basis of self-reported symptoms, fatigue characteristics, and medical diagnoses, according to established criteria (21).

Data analyses

Analyses compared the health of PGW veterans with that of non-PGW veterans using several health indicators, including 1) general health status, 2) medical and psychiatric conditions reported to have been diagnosed or treated by a physician since 1990, 3) symptoms persisting over the prior year, and 4) defined symptom complexes (Gulf War illness, Centers for Disease Control and Prevention-defined multisymptom illness, chronic fatigue syndrome). The incidence of physician-diagnosed conditions and the prevalence of symptoms were assessed among veterans who did not have each problem prior to 1990. All outcomes among non-PGW veterans were stratified by veterans' self-reported receipt of vaccines or injections from the military during the index year.

Among both PGW and non-PGW veterans, health outcomes were frequently associated with veterans' sex, age, income level, and education level. Therefore, all analyses controlled for the effects of these variables. Indicators of general health status were compared using Mantel-Haenszel chi-square tests (23). Odds ratios for the association of deployment and vaccine status with conditions diagnosed or treated by a physician and prevalence odds ratios associated with chronic symptoms were determined using logistic regression. Prevalence odds ratios for defined symptom complexes were also determined by logistic regression, controlling for military as well as demographic variables.

Statistical analyses were performed using SAS version 6.12 computer software (24).

RESULTS

Study population

Of 3,138 veterans randomly selected for contact and screening, 2,396 (76 percent) were located using in-state contact information. Twenty-four of those located were unable to participate because family members reported them as being deceased, hospitalized, or unreachable by telephone. Of the remaining veterans, 7 percent were ineligible for the study because they did not fulfill residency or military service requirements. The remaining 2,211 veterans were invited to be interviewed for the study; 2,030 (92 percent) agreed and 181 declined. PGW veterans (93 percent vs. 88 percent non-PGW) and women (95 percent vs. 91 percent males) were significantly more likely to agree to participate. Characteristics of the target and study populations are provided in table 1.

TABLE 1.

Distribution of January 1991 characteristics of Kansas Gulf War-era veterans and interviewed sample

 All Kansas PGW*-era veterans
 
Interviewed veterans
 
% of PGW (n = 6,235) % of non-PGW* (n = 10,331) % of total (n = 16,566) % of PGW (n = 1,548) % of non-PGW (n = 482) % of total (n = 2,030) 
Demographic characteristics       
 Sex       
  Male 92 86 88 86 87 87 
  Female 14 12 14 13 13 
 Age (years)       
  17–21 26 26 26 19 16 19 
  22–25 26 23 24 22 18 21 
  26–33 26 25 26 27 23 26 
  ≥34 22 26 24 32 42 34 
 Race/ethnicity       
  White 79 83 82 87 91 88 
  Black 15 12 13 
  Hispanic 
  Other 
Military characteristics       
 Component       
  Active 78 89 85 47 42 45 
  Reserve/Guard 22 11 15 53 58 55 
 Branch       
  Army 68 50 56 66 43 61 
  Air Force 11 29 22 16 39 22 
  Navy 13 14 13 11 11 
  Marines 
  Coast Guard <1 
 Rank       
  Enlisted 89 84 86 85 80 84 
  Officer 11 16 14 15 20 16 
 All Kansas PGW*-era veterans
 
Interviewed veterans
 
% of PGW (n = 6,235) % of non-PGW* (n = 10,331) % of total (n = 16,566) % of PGW (n = 1,548) % of non-PGW (n = 482) % of total (n = 2,030) 
Demographic characteristics       
 Sex       
  Male 92 86 88 86 87 87 
  Female 14 12 14 13 13 
 Age (years)       
  17–21 26 26 26 19 16 19 
  22–25 26 23 24 22 18 21 
  26–33 26 25 26 27 23 26 
  ≥34 22 26 24 32 42 34 
 Race/ethnicity       
  White 79 83 82 87 91 88 
  Black 15 12 13 
  Hispanic 
  Other 
Military characteristics       
 Component       
  Active 78 89 85 47 42 45 
  Reserve/Guard 22 11 15 53 58 55 
 Branch       
  Army 68 50 56 66 43 61 
  Air Force 11 29 22 16 39 22 
  Navy 13 14 13 11 11 
  Marines 
  Coast Guard <1 
 Rank       
  Enlisted 89 84 86 85 80 84 
  Officer 11 16 14 15 20 16 
*

PGW, Persian Gulf War veterans; non-PGW, Persian Gulf War-era veterans who did not serve in the Persian Gulf War.

Distribution among non-PGW veterans differs significantly from that of PGW veterans (p < 0.01).

For 143 (7 percent) of the 2,030 study participants, self-reported deployment status differed from that in military personnel records. This was a particular problem among the 482 veterans whose records indicated they had not served in the war, 70 (15 percent) of whom reported they had. Additional study data (e.g., veteran-reported time period and location of service) were used to clarify deployment status, where possible. Veterans for whom additional study data were insufficient to verify deployment status (n = 50) were excluded from subsequent analyses.

Health indicators among PGW and non-PGW veterans

PGW veterans generally reported worse overall health and more symptoms than did non-PGW veterans (table 2). Forty-seven percent of all PGW veterans reported a lower level of health in 1998 than in 1990, compared with 19 percent of non-PGW veterans. Non-PGW veterans who received vaccines during the war were more likely to report a worsened health status since 1990 than were non-PGW veterans who did not receive vaccines, and the former endorsed a greater number of symptoms.

TABLE 2.

General health status of Kansas Gulf War-era veterans, 1990–1998

 PGW* vs. all non-PGW*
 
Non-PGW only, by vaccine status
 
% PGW (n = 1,545) % non-PGW (n = 435) % receiving vaccines (n = 208) % receiving no vaccines (n = 187) 
Health status in August 1990     
 Excellent 61 59 62 53 
 Good 37 38 37 43 
 Fair/poor 
Health status in 1998     
 Excellent 25 45 47 43 
 Good 51 47 47 48 
 Fair/poor 24 10 
Difference in health status category, 1990–1998     
 Same or better 53 81 78 86 
 Worse 47 19 22 14 
No. of chronic symptoms in 1998     
 0–3 symptoms 42 74 72 77 
 4–6 symptoms 14 13 11 14 
  ≥7 symptoms 44 13 17 
Hospitalized for any reason, 1991–1998 34 31 29 34 
Applied for VA* disability benefits, 1991–1998§ 22 19 13 25 
Believes she/he has had health problems related to 1990–1991 military service 46 11 10 11 
 PGW* vs. all non-PGW*
 
Non-PGW only, by vaccine status
 
% PGW (n = 1,545) % non-PGW (n = 435) % receiving vaccines (n = 208) % receiving no vaccines (n = 187) 
Health status in August 1990     
 Excellent 61 59 62 53 
 Good 37 38 37 43 
 Fair/poor 
Health status in 1998     
 Excellent 25 45 47 43 
 Good 51 47 47 48 
 Fair/poor 24 10 
Difference in health status category, 1990–1998     
 Same or better 53 81 78 86 
 Worse 47 19 22 14 
No. of chronic symptoms in 1998     
 0–3 symptoms 42 74 72 77 
 4–6 symptoms 14 13 11 14 
  ≥7 symptoms 44 13 17 
Hospitalized for any reason, 1991–1998 34 31 29 34 
Applied for VA* disability benefits, 1991–1998§ 22 19 13 25 
Believes she/he has had health problems related to 1990–1991 military service 46 11 10 11 
*

PGW, Persian Gulf War veterans; non-PGW, Persian Gulf War-era veterans who did not serve in the Persian Gulf War; VA, US Department of Veterans Affairs.

Excludes 40 non-PGW veterans who could not recall if they had received vaccines or injections during the war.

Distributions differ significantly (p < 0.05), adjusted for sex, age, income level, and education level.

§

Compensation for service-connected disabilities from the US Department of Veterans Affairs.

A significantly higher proportion of PGW than non-PGW veterans reported being diagnosed or treated by a physician for 10 of 21 types of medical conditions since 1990 (table 3). One condition, hypertension, was significantly higher among non-PGW veterans who had received vaccines than among those who had not (not shown; 11 percent vs. 5 percent, odds ratio (OR) = 2.99, 95 percent confidence interval (CI): 1.19, 7.54).

TABLE 3.

Number and proportion of Kansas Gulf War-era veterans reporting medical conditions diagnosed or treated by a physician, with new onset, 1990–1998

Condition(s) PGW* (n = 1,545)
 
Non-PGW* (n = 435)
 
OR*, 95% CI* 
No. % No. % 
Skin condition(s) (other than skin cancer) 299 21 26 3.83 2.50, 5.87 
Stomach or intestinal condition(s) 219 15 32 2.13 1.43, 3.17 
Depression 179 12 30 1.85 1.22, 2.81 
Arthritis 161 11 24 1.99 1.27, 3.14 
Migraine headaches 160 11 21 2.25 1.39, 3.64 
High cholesterol 155 11 36 1.24 0.84, 1.84 
Chronic fatigue syndrome 142 8.70 3.53, 21.46 
Bronchitis 138 10 19 2.61 1.53, 4.47 
High blood pressure 134 33 1.24 0.82, 1.89 
Allergies 119 10 23 1.41 0.88, 2.26 
Posttraumatic stress disorder 98 4.74 2.05, 10.94 
Asthma 63 2.08 1.02, 4.26 
Alcohol or drug dependence 43 1.47 0.65, 3.31 
Heart disease 37 1.56 0.69, 3.56 
Lung disease 37 <0.5 4.77 1.14, 20.04 
Thyroid condition 30 2.32 0.81, 6.67 
Fibromyalgia 24 <0.5 3.69 0.86, 15.84 
Skin cancer 23 1.17 0.47, 2.90 
Diabetes 21 1.22 0.45, 3.30 
Cancer (other than skin cancer) 18 1.21 0.40, 3.69 
Seizures 15 <0.5 4.17 0.51, 31.90 
Condition(s) PGW* (n = 1,545)
 
Non-PGW* (n = 435)
 
OR*, 95% CI* 
No. % No. % 
Skin condition(s) (other than skin cancer) 299 21 26 3.83 2.50, 5.87 
Stomach or intestinal condition(s) 219 15 32 2.13 1.43, 3.17 
Depression 179 12 30 1.85 1.22, 2.81 
Arthritis 161 11 24 1.99 1.27, 3.14 
Migraine headaches 160 11 21 2.25 1.39, 3.64 
High cholesterol 155 11 36 1.24 0.84, 1.84 
Chronic fatigue syndrome 142 8.70 3.53, 21.46 
Bronchitis 138 10 19 2.61 1.53, 4.47 
High blood pressure 134 33 1.24 0.82, 1.89 
Allergies 119 10 23 1.41 0.88, 2.26 
Posttraumatic stress disorder 98 4.74 2.05, 10.94 
Asthma 63 2.08 1.02, 4.26 
Alcohol or drug dependence 43 1.47 0.65, 3.31 
Heart disease 37 1.56 0.69, 3.56 
Lung disease 37 <0.5 4.77 1.14, 20.04 
Thyroid condition 30 2.32 0.81, 6.67 
Fibromyalgia 24 <0.5 3.69 0.86, 15.84 
Skin cancer 23 1.17 0.47, 2.90 
Diabetes 21 1.22 0.45, 3.30 
Cancer (other than skin cancer) 18 1.21 0.40, 3.69 
Seizures 15 <0.5 4.17 0.51, 31.90 
*

PGW, Persian Gulf War veterans; non-PGW, Persian Gulf War-era veterans who did not serve in the Persian Gulf War; OR, odds ratio; CI, confidence interval.

Odds ratio adjusted for sex, age, income, and education level.

Among veterans who did not have condition prior to 1990.

Table 4 shows the proportion of veterans who reported each of 37 symptoms as persistent problems in the year prior to interview, in the absence of exclusionary conditions. Prevalence odds ratios for the association of symptoms with PGW deployment ranged from 1.95 to 6.63. Among non-PGW veterans, six symptoms, all in the pain and neurologic/cognitive/mood symptom categories, were endorsed by significantly more veterans who received vaccines during the war.

TABLE 4.

Prevalence of chronic symptoms with onset since 1990 among Kansas Gulf War-era veterans reporting no exclusionary conditions

 PGW* vs. all non-PGW*
 
Non-PGW only, by vaccine status
 
% PGW (n =1,435) % non-PGW (n = 409) OR*, 95% CI* % receiving vaccines (n =197) % receiving no vaccines (n = 177) OR 95% CI 
Fatigue/sleep problems         
 Not feeling rested after sleep 42 21 2.69 2.04, 3.54 24 18 1.43 0.83, 2.46 
 Fatigue 36 12 4.10 2.94, 5.72 14 1.77 0.89, 5.68 
 Problems falling or staying asleep 33 14 2.98 2.18, 4.08 15 12 1.22 0.65, 2.31 
 Feeling unwell after exercise or exertion 17 4.28 2.57, 7.13 1.84 0.58, 5.83 
 Moderate or multiple fatigue symptoms 47 21 3.32 2.52, 4.38 25 17 1.46 0.84, 2.55 
Pain symptoms         
 Pain in joints 37 15 3.27 2.40, 4.44 17 11 1.94 1.02, 3.70 
 Pain in muscles 21 4.57 2.90, 7.19 1.89 0.74, 4.81 
 Body pain-hurt all over 16 3.93 2.39, 6.48 3.78 1.13, 12.66 
 Moderate or multiple pain symptoms 34 13 3.57 2.57, 4.98 14 10 2.07 1.01, 4.25 
Neurologic/cognitive/mood symptoms         
 Problems remembering recent information 32 4.92 3.35, 7.21 12 3.02 1.28, 7.11 
 Feeling irritable/angry outbursts 31 5.18 3.47, 7.73 10 2.28 0.94, 5.53 
 Numbness or tingling in extremities 29 14 2.33 1.70, 3.18 17 12 1.63 0.86, 3.08 
 Headaches 29 12 2.96 2.11, 4.15 13 11 1.44 0.73, 2.83 
 Eyes very sensitive to light 25 11 2.62 1.84, 3.74 14 2.25 1.02, 4.94 
 Trouble finding words when speaking 24 4.20 2.76, 6.39 10 4.48 1.61, 12.48 
 Feeling down or depressed 23 2.99 2.07, 4.31 11 1.64 0.78, 3.48 
 Difficulty concentrating 22 4.60 2.92, 7.26 2.51 0.95, 6.64 
 Night sweats 20 5.33 3.21, 8.84 1.68 0.53, 5.29 
 Feeling dizzy, lightheaded, or faint 19 3.35 2.18, 5.17 2.20 0.86, 5.68 
 Low tolerance for heat or cold 18 3.67 2.30, 5.87 1.35 0.51, 3.58 
 Symptomatic response to chemicals, odors 17 4.62 2.73, 7.81 1.63 0.52, 5.06 
 Blurred or double vision 13 2.49 1.55, 4.00 3.53 1.13, 11.03 
 Tremors or shaking 1.95 1.17, 3.25 2.31 0.74, 7.24 
 Moderate or multiple neurologic symptoms 59 27 3.94 3.05, 5.10 32 20 2.07 1.23, 3.45 
Gastrointestinal symptoms         
 Diarrhea 19 3.38 2.18, 5.23 2.60 0.96, 7.02 
 Nausea or upset stomach 17 4.25 2.55, 7.08 1.69 0.59, 4.88 
 Abdominal pain or cramping 15 4.23 2.46, 7.25 2.59 0.75, 8.94 
 Moderate or multiple gastrointestinal symptoms 22 3.63 2.38, 5.53 3.13 1.17, 8.32 
Respiratory symptoms         
 Difficulty breathing or catching breath 18 4.09 2.49, 6.71 0.91 0.34, 2.42 
 Persistent cough when don't have cold 17 2.20 1.49, 3.26 1.18 0.55, 2.52 
 Wheezing in chest 13 2.51 1.57, 4.01 0.89 0.35, 2.23 
 Moderate or multiple respiratory symptoms 21 3.37 2.19, 5.18 0.81 0.35, 1.87 
Skin symptoms         
 Rashes 20 5.73 3.41, 9.62 1.03 0.33, 3.22 
 Moderate or multiple skin symptoms 19 4.09 2.53, 6.63 1.70 0.56, 5.15 
Other symptoms         
 Sinus congestion 33 15 2.64 1.90, 3.68 17 13 1.37 0.70, 2.68 
 Ringing in ears 23 4.06 2.60, 6.34 1.91 0.72, 5.09 
 Hearing loss 19 3.34 2.13, 5.23 1.68 0.65, 4.38 
 Problems with teeth or gums 14 2.04 1.33, 3.14 1.03 0.44, 2.42 
 Sore or swollen glands in neck 12 2.94 1.73, 5.01 1.25 0.40, 3.87 
 Sore throat 11 2.39 1.42, 4.03 1.44 0.49, 4.26 
 Unusual hair loss 10 5.79 2.67, 12.52 1.64 0.30, 8.87 
 Veteran or partner feels a burning sensation after sex 3.75 1.88, 7.49 2.20 0.52, 9.25 
 Mouth sores 6.63 2.68, 16.38 1.25 0.20, 7.86 
 PGW* vs. all non-PGW*
 
Non-PGW only, by vaccine status
 
% PGW (n =1,435) % non-PGW (n = 409) OR*, 95% CI* % receiving vaccines (n =197) % receiving no vaccines (n = 177) OR 95% CI 
Fatigue/sleep problems         
 Not feeling rested after sleep 42 21 2.69 2.04, 3.54 24 18 1.43 0.83, 2.46 
 Fatigue 36 12 4.10 2.94, 5.72 14 1.77 0.89, 5.68 
 Problems falling or staying asleep 33 14 2.98 2.18, 4.08 15 12 1.22 0.65, 2.31 
 Feeling unwell after exercise or exertion 17 4.28 2.57, 7.13 1.84 0.58, 5.83 
 Moderate or multiple fatigue symptoms 47 21 3.32 2.52, 4.38 25 17 1.46 0.84, 2.55 
Pain symptoms         
 Pain in joints 37 15 3.27 2.40, 4.44 17 11 1.94 1.02, 3.70 
 Pain in muscles 21 4.57 2.90, 7.19 1.89 0.74, 4.81 
 Body pain-hurt all over 16 3.93 2.39, 6.48 3.78 1.13, 12.66 
 Moderate or multiple pain symptoms 34 13 3.57 2.57, 4.98 14 10 2.07 1.01, 4.25 
Neurologic/cognitive/mood symptoms         
 Problems remembering recent information 32 4.92 3.35, 7.21 12 3.02 1.28, 7.11 
 Feeling irritable/angry outbursts 31 5.18 3.47, 7.73 10 2.28 0.94, 5.53 
 Numbness or tingling in extremities 29 14 2.33 1.70, 3.18 17 12 1.63 0.86, 3.08 
 Headaches 29 12 2.96 2.11, 4.15 13 11 1.44 0.73, 2.83 
 Eyes very sensitive to light 25 11 2.62 1.84, 3.74 14 2.25 1.02, 4.94 
 Trouble finding words when speaking 24 4.20 2.76, 6.39 10 4.48 1.61, 12.48 
 Feeling down or depressed 23 2.99 2.07, 4.31 11 1.64 0.78, 3.48 
 Difficulty concentrating 22 4.60 2.92, 7.26 2.51 0.95, 6.64 
 Night sweats 20 5.33 3.21, 8.84 1.68 0.53, 5.29 
 Feeling dizzy, lightheaded, or faint 19 3.35 2.18, 5.17 2.20 0.86, 5.68 
 Low tolerance for heat or cold 18 3.67 2.30, 5.87 1.35 0.51, 3.58 
 Symptomatic response to chemicals, odors 17 4.62 2.73, 7.81 1.63 0.52, 5.06 
 Blurred or double vision 13 2.49 1.55, 4.00 3.53 1.13, 11.03 
 Tremors or shaking 1.95 1.17, 3.25 2.31 0.74, 7.24 
 Moderate or multiple neurologic symptoms 59 27 3.94 3.05, 5.10 32 20 2.07 1.23, 3.45 
Gastrointestinal symptoms         
 Diarrhea 19 3.38 2.18, 5.23 2.60 0.96, 7.02 
 Nausea or upset stomach 17 4.25 2.55, 7.08 1.69 0.59, 4.88 
 Abdominal pain or cramping 15 4.23 2.46, 7.25 2.59 0.75, 8.94 
 Moderate or multiple gastrointestinal symptoms 22 3.63 2.38, 5.53 3.13 1.17, 8.32 
Respiratory symptoms         
 Difficulty breathing or catching breath 18 4.09 2.49, 6.71 0.91 0.34, 2.42 
 Persistent cough when don't have cold 17 2.20 1.49, 3.26 1.18 0.55, 2.52 
 Wheezing in chest 13 2.51 1.57, 4.01 0.89 0.35, 2.23 
 Moderate or multiple respiratory symptoms 21 3.37 2.19, 5.18 0.81 0.35, 1.87 
Skin symptoms         
 Rashes 20 5.73 3.41, 9.62 1.03 0.33, 3.22 
 Moderate or multiple skin symptoms 19 4.09 2.53, 6.63 1.70 0.56, 5.15 
Other symptoms         
 Sinus congestion 33 15 2.64 1.90, 3.68 17 13 1.37 0.70, 2.68 
 Ringing in ears 23 4.06 2.60, 6.34 1.91 0.72, 5.09 
 Hearing loss 19 3.34 2.13, 5.23 1.68 0.65, 4.38 
 Problems with teeth or gums 14 2.04 1.33, 3.14 1.03 0.44, 2.42 
 Sore or swollen glands in neck 12 2.94 1.73, 5.01 1.25 0.40, 3.87 
 Sore throat 11 2.39 1.42, 4.03 1.44 0.49, 4.26 
 Unusual hair loss 10 5.79 2.67, 12.52 1.64 0.30, 8.87 
 Veteran or partner feels a burning sensation after sex 3.75 1.88, 7.49 2.20 0.52, 9.25 
 Mouth sores 6.63 2.68, 16.38 1.25 0.20, 7.86 
*

PGW, Persian Gulf War veterans; non-PGW, Persian Gulf War-era veterans who did not serve in the Persian Gulf War; OR, prevalence odds ratio; CI, confidence interval.

Excludes 35 non-PGW veterans who could not recall if they had received vaccines or injections during the war.

Prevalence odds ratio adjusted for sex, age, income, and education level.

Prevalence of symptom-defined health outcomes

A certain level of morbidity was common to all veterans, independent of deployment status. The proportion of veterans reporting any exclusionary condition was similar among PGW and non-PGW veterans (7 percent vs. 6 percent, p = 0.41), as was the proportion reporting moderate or multiple symptoms in only one or two defined symptom groups (30 percent vs. 29 percent, p = 0.78). For symptomatology in three or more symptom groups, however, a significant difference by deployment status emerged. This pattern of morbidity—moderate or multiple symptoms in at least three of the six defined groups, in the absence of diagnosed exclusionary conditions—was associated with deployment to the Gulf War and defined “Gulf War illness” for purposes of the present study.

Table 5 provides estimates of prevalence and prevalence odds ratios for the association of Gulf War illness with deployment and vaccine status. A similar pattern of association between PGW deployment, vaccine status, and illness was observed for Gulf War illness, Centers for Disease Control and Prevention-defined multisymptom illness, and chronic fatigue syndrome.

TABLE 5.

1998 prevalence of symptom-defined health outcomes in Kansas Gulf War-era veterans

 Total Gulf War illness (Kansas defined) CDC*-defined multisymptom illness Chronic fatigue syndrome 
No. Pre-valence (%) OR*, 95% CI* No. Pre-valence (%) OR 95% CI No. Pre-valence (%) OR 95% CI 
PGW* vs. all non-PGW* veterans              
 All non-PGW veterans 435 36 8.3 1.0  86 19.8 1.0  0.7 1.0  
 PGW veterans 1,545 529 34.2 4.68 3.25, 6.75 729 47.2 3.26 2.48, 4.28 110  8.21 2.58,26.10 
PGW vs. non-PGW veterans, by vaccine status              
 Non-PGW veterans/no vaccines 187 3.7 1.0  28 15.0 1.0    
 Non-PGW veterans/received vaccines 208 24 11.5 3.78 1.50, 9.54 48 23.1 2.04 1.15, 3.60 1.4 Undefined  
 PGW veterans 1,545 529 34.2 10.64 4.91, 23.06 729 47.2 4.77 3.07, 7.41 110 7.1 Undefined  
 Total Gulf War illness (Kansas defined) CDC*-defined multisymptom illness Chronic fatigue syndrome 
No. Pre-valence (%) OR*, 95% CI* No. Pre-valence (%) OR 95% CI No. Pre-valence (%) OR 95% CI 
PGW* vs. all non-PGW* veterans              
 All non-PGW veterans 435 36 8.3 1.0  86 19.8 1.0  0.7 1.0  
 PGW veterans 1,545 529 34.2 4.68 3.25, 6.75 729 47.2 3.26 2.48, 4.28 110  8.21 2.58,26.10 
PGW vs. non-PGW veterans, by vaccine status              
 Non-PGW veterans/no vaccines 187 3.7 1.0  28 15.0 1.0    
 Non-PGW veterans/received vaccines 208 24 11.5 3.78 1.50, 9.54 48 23.1 2.04 1.15, 3.60 1.4 Undefined  
 PGW veterans 1,545 529 34.2 10.64 4.91, 23.06 729 47.2 4.77 3.07, 7.41 110 7.1 Undefined  
*

CDC, Centers for Disease Control and Prevention; OR, prevalence odds ratio; CI, confidence interval; PGW, Persian Gulf War veterans; non-PGW, Persian Gulf War-era veterans who did not serve in the Persian Gulf War.

Prevalence odds ratio adjusted for sex, age, income, education, rank, and service branch and component.

Excludes 40 veterans who could not recall if they had received vaccines or injections during the war.

Distribution of Gulf War illness in PGW veterans

The prevalence of Gulf War illness among PGW demographic, military, and deployment subgroups is shown in table 6, with unadjusted and adjusted prevalence odds ratios. After adjustment, the prevalence of Gulf War illness was significantly elevated among women, veterans with lower household incomes and less education, Army veterans, and enlisted personnel.

TABLE 6.

1998 prevalence of Gulf War illness (GWI) among Kansas Gulf War veterans, stratified by demographic, military, and wartime service characteristics

 Total % with GWI Unadjusted
 
Adjusted
 
OR* 95% CI* OR 95% CI 
Demographic characteristics       
 Sex       
  Male 1,358 33 1.0  1.0  
  Female 187 41 1.36 1.00, 1.87 1.49 1.06, 2.08 
 Age (years)       
  24–29 362 35 1.0  1.0  
  30–39 621 36 1.07 0.82, 1.41 1.16 0.86, 1.57 
  40–49 374 34 0.96 0.71, 1.31 1.23 0.84, 1.80 
≥50 188 27 0.68 0.46, 1.00 1.40 0.83, 2.34 
 Race       
  White 1,309 33 1.0  1.0  
  Black 112 48 1.93 1.32, 2.83 1.23 0.81, 1.87 
  Other 118 39 1.32 0.90, 1.95 1.08 0.70, 1.65 
 Annual income ($)       
≥35,000 931 31 1.0  1.0  
  <35,000 577 41 1.56 1.26, 1.93 1.30 1.02, 1.66 
 Education       
≥4-year college degree 436 24 1.0  1.0  
  <4-year college degree 1,102 38 1.93 1.51, 2.48 1.60 1.18, 2.15 
Military characteristics, 1990–1991       
 Branch       
  Air Force 284 19 1.0  1.0  
  Navy 176 23 1.32 0.84, 2.09 1.18 0.62, 2.21 
  Marines 94 33 2.14 1.28, 3.60 1.26 0.65, 2.44 
  Army 991 41 3.00 2.19, 4.11 1.71 1.12, 2.61 
 Component       
  Active 687 36 1.0  1.0  
  Reserves 507 38 1.08 0.85, 1.37 1.21 0.93, 1.59 
  National Guard 348 26 0.62 0.47, 0.83 1.10 0.77, 1.58 
 Rank       
  Officer 224 18 1.0  1.0  
  Enlisted 1,318 37 2.61 1.84, 3.69 1.70 1.12, 2.58 
Time and location of Gulf War service       
 Months in theater (August 1990–July 1991)       
  1–3 months 290 26 1.0  1.0  
  4–6 months 889 37 1.66 1.24, 2.23 0.91 0.63, 1.32 
  7–12 months 350 36 1.61 1.15, 2.27 1.01 0.65, 1.60 
 Notified of proximity to Khamisiyah demolition site       
  No 1,156 33 1.0  1.0  
  Yes 271 42 1.47 1.12, 1.92 1.28 0.95, 1.73 
 Location in theater       
  On board ship 121 21 1.0  1.0  
  Saudi Arabia/Bahrain (not Iraq/Kuwait) 792 31 1.64 1.04, 2.58 1.73 0.99, 3.04 
  Entered Iraq/Kuwait 606 42 2.62 1.67, 4.11 2.73 1.52, 4.90 
 Time period in theater       
  Left Gulf area prior to January 1991 56 1.0  1.0  
  Present during war, left March 1991 295 25 3.35 1.35, 8.33 3.27 1.19, 8.96 
  Present during war, left April–May 1991 779 36 5.85 2.56, 13.40 3.22 1.17, 8.83 
  Present during war, left June–July 1991 311 43 7.72 3.38, 17.66 11.70 3.16, 43.40 
 Total % with GWI Unadjusted
 
Adjusted
 
OR* 95% CI* OR 95% CI 
Demographic characteristics       
 Sex       
  Male 1,358 33 1.0  1.0  
  Female 187 41 1.36 1.00, 1.87 1.49 1.06, 2.08 
 Age (years)       
  24–29 362 35 1.0  1.0  
  30–39 621 36 1.07 0.82, 1.41 1.16 0.86, 1.57 
  40–49 374 34 0.96 0.71, 1.31 1.23 0.84, 1.80 
≥50 188 27 0.68 0.46, 1.00 1.40 0.83, 2.34 
 Race       
  White 1,309 33 1.0  1.0  
  Black 112 48 1.93 1.32, 2.83 1.23 0.81, 1.87 
  Other 118 39 1.32 0.90, 1.95 1.08 0.70, 1.65 
 Annual income ($)       
≥35,000 931 31 1.0  1.0  
  <35,000 577 41 1.56 1.26, 1.93 1.30 1.02, 1.66 
 Education       
≥4-year college degree 436 24 1.0  1.0  
  <4-year college degree 1,102 38 1.93 1.51, 2.48 1.60 1.18, 2.15 
Military characteristics, 1990–1991       
 Branch       
  Air Force 284 19 1.0  1.0  
  Navy 176 23 1.32 0.84, 2.09 1.18 0.62, 2.21 
  Marines 94 33 2.14 1.28, 3.60 1.26 0.65, 2.44 
  Army 991 41 3.00 2.19, 4.11 1.71 1.12, 2.61 
 Component       
  Active 687 36 1.0  1.0  
  Reserves 507 38 1.08 0.85, 1.37 1.21 0.93, 1.59 
  National Guard 348 26 0.62 0.47, 0.83 1.10 0.77, 1.58 
 Rank       
  Officer 224 18 1.0  1.0  
  Enlisted 1,318 37 2.61 1.84, 3.69 1.70 1.12, 2.58 
Time and location of Gulf War service       
 Months in theater (August 1990–July 1991)       
  1–3 months 290 26 1.0  1.0  
  4–6 months 889 37 1.66 1.24, 2.23 0.91 0.63, 1.32 
  7–12 months 350 36 1.61 1.15, 2.27 1.01 0.65, 1.60 
 Notified of proximity to Khamisiyah demolition site       
  No 1,156 33 1.0  1.0  
  Yes 271 42 1.47 1.12, 1.92 1.28 0.95, 1.73 
 Location in theater       
  On board ship 121 21 1.0  1.0  
  Saudi Arabia/Bahrain (not Iraq/Kuwait) 792 31 1.64 1.04, 2.58 1.73 0.99, 3.04 
  Entered Iraq/Kuwait 606 42 2.62 1.67, 4.11 2.73 1.52, 4.90 
 Time period in theater       
  Left Gulf area prior to January 1991 56 1.0  1.0  
  Present during war, left March 1991 295 25 3.35 1.35, 8.33 3.27 1.19, 8.96 
  Present during war, left April–May 1991 779 36 5.85 2.56, 13.40 3.22 1.17, 8.83 
  Present during war, left June–July 1991 311 43 7.72 3.38, 17.66 11.70 3.16, 43.40 
*

OR, prevalence odds ratio; CI, confidence interval.

Prevalence odds ratio adjusted for sex, income, education level, branch of service, rank, location in theater, and time period in theater.

Age, annual household income, and level of education at time of interview.

Fewer than 10 percent of Kansas veterans served primarily on board ship during the war. Nearly all remaining veterans were stationed for some period of time in Saudi Arabia and/or the island nation of Bahrain off the coast of Saudi Arabia. About 40 percent also entered Iraq and/or Kuwait, countries in which the ground war and coalition air strikes occurred. Overall, veterans who served primarily on board ship were least affected by Gulf War illness. The prevalence of Gulf War illness was somewhat higher among those serving in only Saudi Arabia or Bahrain and highest among those who entered Iraq and/or Kuwait.

Most PGW veterans were present in the Gulf region during the ground and air wars in January and February of 1991. Only 56 (4 percent) left the Gulf area prior to January 1991, and 29 (2 percent) arrived in the area in March 1991 or later. The prevalence of Gulf War illness was lowest among veterans who departed the region prior to the war, higher for those present during the war who left the region by March, and highest for those departing in June or July of 1991.

The association of Gulf War illness with time period differed by location in theater (not shown in table). The prevalence of Gulf War illness was highest among veterans who served in Iraq or Kuwait (42 percent), regardless of when they left the region. For veterans not in Iraq or Kuwait, Gulf War illness occurred in 9 percent of those departing prior to the war (referent), 21 percent of those departing in March (OR = 2.86, 95 percent CI: 1.05, 7.78), 32 percent of those departing in April or May (OR = 3.55, 95 percent CI: 1.28, 9.84), and 41 percent of those departing in June or July (OR = 10.31, 95 percent CI: 2.61, 40.78). This pattern was maintained after adjusting for the number of months veterans spent in the region, with odds ratios ranging from 2.54 for veterans leaving the region in March to 6.04 for those departing in June or July of 1991.

Finally, among non-PGW veterans, Gulf War illness was significantly associated only with self-reported receipt of vaccines (table 5) and being female (OR = 3.19, 95 percent CI: 1.23, 8.29). In multivariable modeling, there was no significant association of Gulf War illness with age, income level, education level, rank, component, or branch of service.

DISCUSSION

The results of this study indicate that, 7 years after serving in the Persian Gulf War, Kansas veterans experienced substantially more health problems than did era veterans who did not serve in the war. Increased morbidity was reflected in worse overall health status, higher rates of medical and psychiatric diagnoses, and more frequent and severe chronic symptoms.

Among Gulf War veterans, the prevalence of Gulf War illness was most strongly associated with the time period and location in which they served. Earlier reports have hinted at similar associations. US PGW veterans were least likely to participate in government registries if they were in the Gulf region before the war and most likely to participate if they served during Desert Storm (25). A report on veterans participating in the US Department of Veterans Affairs' registry suggested that veterans exhibit different illness profiles in connection with their location of service during the war (26). Iowa PGW veterans were found to have more health problems if they served in Iraq, Kuwait, or Saudi Arabia than if they served elsewhere in the region (13). In addition, Kansas Army veterans, enlisted personnel, and women were disproportionately affected by Gulf War illness, supporting previous indications that ground troops, enlisted personnel, and women may have more health problems than other PGW veterans (7, 10, 14, 27).

A question of central importance to veterans, government officials, and healthcare providers is, “How many veterans are affected by Gulf War-related health problems?” The answer depends on how such problems are conceptualized and defined, but a surprisingly consistent estimate for the excess burden of symptom-defined illness is emerging from existing population-based studies. Among four Air National Guard units, 45 percent of PGW veterans and 15 percent of non-PGW veterans met criteria for Centers for Disease Control and Prevention-defined multisymptom illness, an excess of 30 percent associated with PGW deployment (14). Among servicemen from the United Kingdom, 62 percent of PGW and 36 percent of non-PGW veterans met similar criteria, an excess of 26 percent among PGW veterans (15). In the present study, 47 percent of Kansas PGW veterans met criteria for Centers for Disease Control and Prevention-defined multisymptom illness, compared with 20 percent of non-PGW veterans, an excess of 27 percent. In addition, 34 percent of PGW veterans met the more restrictive criteria for Kansas-defined Gulf War illness, compared with 8 percent of non-PGW veterans, an excess of 26 percent among PGW veterans. Thus, using two definitions in three distinct veteran populations, the excess burden of illness associated with deployment to the Gulf War has consistently been between 25 and 30 percent.

Nearly all PGW veterans were likely to have received vaccines prior to or during the war. Inoculations are routinely given in the military prior to overseas duty (28), and about 98 percent of Iowa veterans reported receiving vaccines in association with PGW deployment (13). The results of the present study suggest that non-PGW veterans who received vaccines during the war may experience some of the same health problems as PGW veterans. The observed association of Gulf War illness with vaccines among non-PGW veterans is based on self-reported receipt of vaccines and so must be considered preliminary in nature. It does not appear to be due to a general overreporting of health problems in this group, however, since only one medical condition (hypertension) and two types of symptoms were significantly associated with receiving vaccines. Additionally, non-PGW veterans who received vaccines were no more likely to attribute health problems to their wartime service than were non-PGW veterans who did not receive vaccines.

A relation between vaccinations and illness has been observed among Gulf War veterans from the United Kingdom and Canada, and a mechanism for an association of illness with multiple vaccinations has been proposed (29). The prevalence of multisymptom illness was associated with reports by veterans from the United Kingdom of receiving vaccines against biologic warfare agents (anthrax, plague, pertussis adjuvant) and with receiving multiple vaccinations during deployment (15, 30). A 1998 study of Canadian Gulf War veterans found a significant association between receiving “nonroutine immunizations” (anthrax, plague) and several symptom-defined outcomes (10).

Patterns associated with where and when a veteran served suggest that multiple factors likely contributed to the excess morbidity experienced by Gulf War-era veterans. Fewer than 4 percent of era veterans with no identified PGW-related exposures experienced symptoms of Gulf War illness. Between 9 and 12 percent of veterans likely to have had the lowest level of Gulf War-related exposures (non-PGW veterans who received vaccines during the war and veterans returning from the Gulf region prior to Desert Storm) had symptoms of Gulf War illness. The highest rate of illness, independent of time period, occurred among veterans who were in Iraq and/or Kuwait, suggesting that the factor or factors contributing to Gulf War illness were most concentrated in battlefield areas. Veterans in those areas might have encountered a greater number or concentration of potentially toxic exposures and experienced more battle-related trauma.

The observation that veterans in support areas who departed the region soon after the war were less likely to be ill than those who departed months later is particularly intriguing. It suggests an association of illness with toxic exposures, since battle-related stressors were reduced in later months. Potential risk factors that would have been more prevalent in support areas in later months might include exposure to contaminants from oil well fires, exposure to toxicants transferred via people or equipment from battlefield areas, and exposures associated with cleanup and refurbishing of equipment.

The results of this study raise methodological issues likely to be important in other Gulf War-related research. Fifteen percent of Gulf War-era veterans whose military records indicated they had not served in the Gulf War reported that they had. If the discrepancies observed here are representative, large studies of Gulf War-era military populations that rely on military personnel databases to compare outcomes between PGW and non-PGW veterans may be seriously affected by inaccurate assessment of deployment status.

Another important methodological issue relates to the use of non-PGW veterans as an “unexposed” referent group in cross-sectional and cohort studies. If vaccines administered to troops are one of the factors contributing to excess morbidity in Gulf War veterans, studies comparing PGW with non-PGW veterans should assess and control for the effects of vaccines received by non-PGW veterans.

There are limitations to consider in interpreting the findings reported here. First, all health and most military information was self-reported. The considerable amount of media attention given to issues surrounding Gulf War-related health problems may have generated an increased awareness of symptoms among PGW veterans and an increased willingness to report them. The possible impact of differential recall or reporting on apparent increases in morbidity among Gulf War veterans is difficult to quantify but has been assessed in previous studies. A large national survey of Gulf War-era veterans found that veteran-reported information relating to clinical encounters was in good agreement with medical records in 93 percent of cases and in partial agreement in 4–6 percent of cases (31). The Iowa Persian Gulf Study Group, using measures of physical function and veterans' tendency to respond to questions in a socially desirable way, concluded that recall bias may not explain the higher prevalence of health problems observed among PGW veterans (13). It is also unlikely that increased symptom awareness or reporting among PGW veterans would fully account for the high odds ratios associated with Gulf War illness in the present study. In particular, media influence would not explain the nonrandom distribution of Gulf War illness observed here, since associations of illness with time and place of Gulf War service have not been widely reported.

Limitations generally associated with self-reported exposures in the Gulf War theater were minimized in this study by including only more objective service-related indicators—rank, branch of service, dates of service, and the countries in which veterans served. The accuracy of self-reported receipt of vaccines by non-PGW veterans is open to question, however, and could have biased the associations observed here in either direction.

Further, it is not known whether the health experience of Kansas veterans is representative of Gulf War veterans nationally. Overall, Kansas Gulf War veterans were similar to their national peers with respect to rank, gender, and age distribution but included fewer non-Caucasians and a lower proportion of Navy and Marine Corps veterans (25). Still, the prevalence of Centers for Disease Control and Prevention-defined multisymptom illness observed in Kansas veterans was similar to that found among Air National Guard units (14), and the estimated prevalence of chronic fatigue syndrome in Kansas PGW veterans (7 percent) was similar to that reported from a nationwide survey of PGW veterans (5 percent) (27).

Over a decade after Iraq invaded Kuwait, the health problems reported by Gulf War veterans remain largely an unsolved mystery. These health problems appear to be complex, and their understanding will likely require an approach that considers “clusters of causes” and “combinations of effects” (32). The basic epidemiologic approach taken here—describing excess health problems reported by veterans and their association with person, place, and time—provides answers to preliminary questions and suggests areas of follow-up that might produce useful insights regarding etiology and illness subtypes. Such investigations should include comparisons between veteran subgroups with higher and lower rates of illness and among those with different types of symptoms. In this way, as the results of this study and of other recent studies suggest, many of the outstanding questions regarding Gulf War-related health problems may be answerable.

Reprint requests to Dr. Lea Steele, Kansas Commission on Veterans Affairs, 700 S.W. Jackson, Suite 701, Topeka, KS 66603 (e-mail: kspgwvets@cjnetworks.com).

This study was funded by the state of Kansas.

The author gratefully acknowledges members of the Kansas Persian Gulf War Veterans Health Initiative Advisory Board: Jim Bunker, Robert Hayes, Jeff Lawson, Dr. John Neuberger, Dr. Fred Oehme, Sharon Raby, Larry Salmans, and Dan Thimesch, as well as Don Myer for advice and support in project development. The author also thanks Dr. John Neuberger, Jeff Ford, Dr. Walter Schumm, and Dr. Tony Jurich for suggestions regarding questionnaire development; Dr. Robert Poresky, Dr. Minakshi Tikoo, and Jeremy Yorgason for supervising computer-assisted telephone interviewing data collection; the Defense Manpower Data Center for providing data on Kansas veterans; the Information Network of Kansas for assistance with state data; Jay Hemenway, Nicole Charles, and Amy Meier for assistance in locating veterans; Jill Covert and Rebecca Smith for assistance in data management; and Dr. Jeff Levin, Dr. Fred Oehme, Dr. John Neuberger, and Dr. Irving Cohen for helpful suggestions on earlier versions of this manuscript. Special acknowledgment is given to Dan Thimesch, whose persistent efforts made this study possible.

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