Effects of demographic, dietary and other lifestyle factors on the prevalence of hyperlipidemia in Guangxi Hei Yi Zhuang and Han populations

Background

Han is the largest nationality and Zhuang is the largest minority among 56 nationalities in China. Hei Yi (means black-worship and black dressing) Zhuang is a special subgroup of 43 ethnic subgroups of Zhuang. There are limited data about the effect of environmental factors on the prevalence of hyperlipidemia in this population. The aim of this study was to determine the effects of demographic, dietary, and other lifestyle factors on the prevalence of hyperlipidemia in Hei Yi Zhuang and Han populations.

Design

We performed a cross-sectional study of 1166 randomly selected people of Hei Yi Zhuang aged 7–84 years from seven villages in Napo County, Guangxi, China; and 1018 people of Han aged 6–89 years from nine villages in the same region.

Methods

Information on demographic characteristics, dietary patterns, and other lifestyle factors was collected by standard questionnaires. Blood pressure, height, weight, waist circumference, serum lipids and apolipoproteins were measured, and body mass index (BMI) was calculated as a measure of weight relative to height.

Results

The prevalence rates of hypercholesterolemia, hypertriglyceridemia and hyperlipidemia in Hei Yi Zhuang and Han were 23.6 versus 27.0% (P > 0.05), 12.3 versus 14.4% (P > 0.05) and 29.9 versus 34.2% (P < 0.05), respectively. The prevalence of hyperlipidemia was positively correlated with age, BMI and blood pressure (P < 0.05- 0.001) in Hei Yi Zhuang, whereas it was positively associated with age, BMI, blood pressure and alcohol consumption in Han (P < 0.01-0.001). There was no significant correlation between the prevalence of hyperlipidemia and sex or cigarette smoking in Hei Yi Zhuang, Han or a combined population of Hei Yi Zhuang and Han (P > 0.05), and alcohol consumption in Hei Yi Zhuang (P > 0.05).

Conclusion

The current study reveals that there is a significant difference in the prevalence of hyperlipidemia and its risk factors between Hei Yi Zhuang and Han, which might result from different demographic characteristics, dietary habits and other lifestyle factors.

cross-sectional study, diet, hyperlipidemia, prevalence, risk factors

Introduction

The roles of plasma or serum cholesterol [1], triglyceride (TG) [2], low-density lipoprotein cholesterol (LDL-C) [3] and apolipoprotein (Apo) B [4] in atherogenesis and coronary artery disease have been clearly documented. Furthermore, it has been noted that the strength of the relationships between blood lipid levels and atherosclerosis might be influenced by several lifestyle-related factors, such as cigarette smoking, physical activity and psychosocial conditions. In particular, the Framingham Heart Study first reported that glucose intolerance, blood pressure levels and smoking habits modify the effect of total cholesterol (TC) on cardiovascular risk [5]. It is also well known that dietary patterns, such as the Mediterranean diet, are strongly related with blood lipid levels, as well as with the prevalence and the management of dyslipidemia [6]. Recently, although Yusuf et al. [7] reported that, among others, smoking, dietary habits and alcohol intake, as well as a lack of regular physical activity, account for most of the risk of myocardial infarction worldwide in both sexes and at all ages in all regions, very few studies have evaluated the role of diet and other lifestyle-related factors in the prevalence of hyperlipidemia in minority groups.

There are 56 nationalities in China. Han is the largest nationality, and Zhuang is the largest minority. Geographically and linguistically, Zhuang can be classified into 43 ethnic subgroups, among which Hei Yi (means black-worship and black dressing) Zhuang proved to be the most conservative subgroup. They hold that the color black is beautiful, and like to wear black garments and pants. Black color has become the mark of Hei Yi Zhuang. The population of Hei Yi Zhuang is 51655. Because of their remoteness, due to continuous mountain ranges, blocking of passes, an abominable environment, as well as strict intra-nationality marriages, the special customs and culture of this population are still preserved [8]. Little information is available about the associations between lifestyle factors, such as nutrient intakes and lipid profile, in this population. Therefore, the present study was undertaken to compare the effects of demographic characteristics, dietary patterns and other lifestyle factors on the prevalence of hyperlipidemia between Hei Yi Zhuang and Han populations from the same region.

Methods

Subjects

A total of 1166 people of Hei Yi Zhuang from seven villages in Napo County, Guangxi Zhuang Autonomous Region, China were randomly selected according to the population register of each village. The ages of the subjects ranged from 7 to 84 years, with an average age of 44.00 ± 17.54 years. There were 541 males (46.40%) and 625 females (53.60%). All subjects were peasants. There were 98 people aged < 20 years (8.40%), 156 people aged 20–29 years (13.38%), 255 people aged 30–39 years (21.87%), 177 people aged 40–49 years (15.18%), 196 people aged 50–59 years (16.81%), 196 people aged 60–69 years (16.81%), 76 people aged 70–79 years (6.52%) and 12 people aged 80 years and over (1.03%). The subjects accounted for 2.26% of the total Hei Yi Zhuang population. At the same time, a total of 1018 people of Han from nine villages in the same county were also surveyed by the same method. The mean age of the subjects was 42.95 ± 17.11 years (range 6–89 years). There were 426 men (41.85%) and 592 women (58.15%). All of them were also peasants. There were 85 people aged < 20 years (8.35%), 183 people aged 20–29 years (17.98%), 230 people aged 30–39 years (22.59%), 173 people aged 40–49 years (16.99%), 149 people aged 50–59 years (14.64%), 117 people aged 60–69 years (11.49%), 73 people aged 70–79 years (7.17%) and eight people aged 80 years or older (0.79%). All of these subjects were essentially healthy and had no evidence of any chronic illness, including hepatic, renal, thyroid, or cardiac dysfunction. They were not taking medications known to affect serum lipid levels (lipid-lowering drugs such as statins or fibrates, beta-blockers, diuretics or hormones). This study was approved by our institutional ethics committee, and the study participants gave informed consent.

Epidemiological survey

The survey was performed using internationally standardized methods. The medical and family history, socioeconomic and personal information including demography, habitual diet, physical activity, drug use, alcohol consumption, cigarette smoking, occupation, education and other lifestyle behaviors were obtained by standard questionnaires. Dietary information about each subject was obtained using a 24-h dietary recall method [9]. Detailed descriptions of all foods, beverages and supplements consumed during the 24-h period before the interview, including the quantity, cooking method and brand names, were recorded by a chief physician. Quantitative estimate of cumulative nutrient intake per day in each food was based on food tables derived from the 2002 Chinese food composition tables [10]. Overall physical activity was ascertained with the use of a modified version of the Harvard Alumni Physical Activity Questionnaire [11], which included questions about the number of hours per day (mean of a regular weekday and a regular weekend day) spent sleeping and in sedentary, light, moderate and vigorous activities; the interviewer ensured that the total time added up to 24h. The physical examination included blood pressure, height, weight and waist circumference. Systolic and diastolic blood pressure readings were taken with a standard mercury sphygmomanometer after at least 5 min of rest, while the subject was in a sitting position. The values used in the current analysis are means of three measurements taken by the same investigator at about 0.5-h intervals. Systolic blood pressure was determined by the first Korotkoff sound, and diastolic blood pressure by the fifth Korotkoff sound. Body weight, to the nearest 100 g, was measured using a portable balance scale. Subjects were weighed without shoes and in a minimum of clothing. Height was measured, to the nearest 0.5 cm, using a portable steel measuring device. From these two measurements body mass index (BMI, kg/m²) was calculated. Waist circumference was measured with a nonstretchable measuring tape, at the level of the smallest area of the waist, to the nearest 0.1 cm.

Measurements of lipids and apolipoproteins

Blood samples were obtained from an antecubital vein in all subjects after an overnight fast. The blood was transferred into glass tubes and allowed to clot at room temperature. Immediately following clotting, serum was separated by centrifugation for 15 min at 3000 rpm. The levels of TC, TG, high-density lipoprotein cholesterol (HDL-C) and LDL-C in samples were determined enzymatically using commercially available kits, Tcho-1, TG-LH (Randox Laboratories Ltd., Antrim, Northern Ireland), Cholestest N HDL and Cholestest LDL (Daiichi Pure Chemicals Co. Ltd., Tokyo, Japan), respectively. Apo A1 and Apo B levels were measured by an immunoturbidimetric assay (Randox Laboratories Ltd.). All determinations were performed with an autoanalyzer (Type 7170A; Hitachi Ltd., Tokyo, Japan) in our Clinical Science Experiment Center, the First Affiliated Hospital, Guangxi Medical University.

Diagnostic criteria

The normal values of serum TC, TG, HDL-C, LDL-C, Apo A1, Apo B, and the ratio of Apo A1 to Apo B in our Clinical Science Experiment Center were 3.10–5.17, 0.56–1.70, 0.91–1.81, 1.70–3.20 mmol/l, 1.00–1.76, 0.63–1.14 g/l, and 1.00–2.50, respectively. Individuals with TC > 5.17 mmol/l and/or TG > 1.70 mmol/l were defined as hyperlipidemic [8]. Hypertension was defined as a systolic pressure of 140 mmHg or higher and a diastolic pressure of 90 mm Hg or higher [12]. The subjects with BMI > 24 kg/m² were diagnosed as overweight, and > 28 kg/m² as obese [13].

Statistical analysis

The data were organized and analyzed using Excel XP (Microsoft, Seattle, Washington, USA) and SPSS for Windows version 10.0 (SPSS Inc., Chicago, Illinois, USA). Means and standard deviation (SD) as well as frequency distributions of participant characteristics were calculated. The difference of two parameters was tested by the Student's unpaired t-test. One-way analysis of variance (ANOVA) was performed to assess the differences of three and more parameters. Significant differences were then subjected to multiple comparison using the New-man-Keuls test. Differences of percentage were tested by the chi-squared test. In order to evaluate the association of hyperlipidemia and sex (female = 0; male = 1), age (< 20 = 1; 20–29 = 2; 30–39 = 3; 40–49 = 4; 50–59 = 5; 60–69 = 6; 70–79 = 7; ≥ 80 = 8), BMI (≤ 24 kg/m² = 0; > 24 kg/m² = 1), blood pressure (normotensives = 0; hypertensives = 1), alcohol consumption (nondrinkers = 0; < 250 g wine/day = 1; 250–499 g/day = 2; ≥ 500 g/day = 3), cigarette smoking (nonsmokers = 0; < 10 cigarettes/day = 1; 10–19 cigarettes/day = 2; 20–39 cigarettes/day = 3; ≥ 40 cigarettes/day = 4), or nationality (Hei Yi Zhuang = 0; Han = 1), unconditional logistic regression analysis was also performed in combined population of Hei Yi Zhuang and Han, Hei Yi Zhuang, and Han; respectively. The backward multiple logistic regression method was used to select the risk factors significantly associated with hyperlipidemia. Total intake of each nutrient was summed over all foods consumed. Matlab5.0 software was used for processing these procedures by the method of multiplication of matrix [14]. A P value of less than 0.05 was considered significant.

Results

Demographic, dietary and other lifestyle factors between Hei Yi Zhuang and Han

The demographic, dietary and other lifestyle characteristics between Hei Yi Zhuang and Han are shown in Table 1. Systolic blood pressure, pulse pressure, prevalence of hypertension, intakes of carbohydrate and table salt were significantly higher in Hei Yi Zhuang than in Han (P < 0.01–0.001), whereas the education level, waist circumference, body weight, BMI, and the intakes of total energy, fat, protein and cholesterol were significantly higher in Han than in Hei Yi Zhuang (P < 0.001 for all). There were no significant differences of physical activity level, body height, diastolic blood pressure, alcohol consumption, cigarette smoking and age between the two ethnic groups (P > 0.05).

Prevalence of hyperlipidemia between Hei Yi Zhuang and Han

As shown in Table 2, the increased rates of TC, TG, HDL-C, LDL-C, Apo B, the ratio of Apo A1 to Apo B, and the decreased rate of Apo A1 were 23.6% (hyper-cholesterolemia), 12.3% (hypertriglyceridemia), 70.7, 9.5, 9.3, 6.4 and 0.9% in Hei Yi Zhuang, and 27.0% (hypercholesterolemia, P > 0.05), 14.4% (hypertriglyceridemia, P > 0.05), 63.5% (P < 0.001), 13.5% (P < 0.001), 14.4% (P < 0.001), 2.4% (P < 0.001) and 0.9% (P > 0.05) in Han, respectively. The increased rate of both TC and TG was 6.0% (70/1166) in Hei Yi Zhuang and 7.3% (74/1018, P > 0.05) in Han. Thus, the prevalence of hyperlipidemia in Hei Yi Zhuang and Han was 29.9% (349/1166) versus 34.2% (348/1018, P < 0.05). The effects of sex, BMI, hypertension, alcohol consumption, cigarette smoking and age on the prevalence of hyperlipidemia between Hei Yi Zhuang and Han are also shown in Table 2.

Risk factors of hyperlipidemia between Hei Yi Zhuang and Han

Unconditional multiple logistic regression analysis shows that the prevalence of hyperlipidemia was positively correlated with age, BMI, blood pressure, alcohol consumption and nationality (Han) in combined population of Hei Yi Zhuang and Han (P < 0.01–0.001); positively correlated with age, BMI, blood pressure and alcohol consumption in Han (P < 0.01–0.001); and positively associated with age, BMI and blood pressure in Hei Yi Zhuang (P < 0.05–0.001) (Table 3). No significant correlation of the prevalence of hyperlipidemia was observed with sex or cigarette smoking in Hei Yi Zhuang, Han or combined population of Hei Yi Zhuang and Han (P > 0.05), and alcohol consumption in Hei Yi Zhuang (P > 0.05).

Table 1

Comparison of demographic, dietary and lifestyle characteristics between Hei Yi Zhuang and Han

Characteristics	Hei Yi Zhuang (n = 1166)	Han nationality (n = 1018)	t (χ2)	P
Age (years)	44.00 ± 17.54	42.95 ± 17.11	1.4116	0.1582
Education status (years)	2.86 ± 0.97	4.13 ± 1.82	20.6978	0.0000
Physical activity (h/week)	39.25 ± 13.75	38.61 ± 14.47	1.0589	0.2898
Height (cm)	152.41 ± 9.05	152.24 ± 8.65	0.4470	0.6549
Weight (kg)	49.22 ± 8.13	51.71 ± 8.56	6.9660	0.0000
Body mass index (kg/m2)	21.08 ± 2.35	22.22 ± 2.62	10.7186	0.0000
> 24 kg/m2 [n (%)]	127 (10.9)	210 (20.6)	39.4848	0.0000
Waist circumference (cm)	72.16 ± 6.77	73.72 ± 7.54	5.0941	0.0000
Systolic blood pressure (mmHg)	124.01 ± 18.64	120.90 ± 16.06	4.1466	0.0000
Diastolic blood pressure (mmHg)	75.85 ± 11.17	76.26 ± 10.12	0.8939	0.3715
Pulse pressure (mmHg)	48.18 ± 14.53	44.69 ± 11.00	6.2565	0.0000
Hypertension [n (%)]	271 (23.2)	163 (16.0)	17.8425	0.0000
Alcohol intake [n (%)]	608 (52.1)	468 (46.0)	8.2821	0.0040
(g wine/day)	337.38 ± 252.96	353.63 ± 128.08	1.2700	0.2044
Cigarette smokers [n (%)]	343 (29.4)	276 (27.1)	1.4216	0.2326
(cigarettes/day)	21.08 ± 8.99	22.39 ± 9.30	1.7745	0.0765
Energy (kJ/day)	8746.72 ± 274.89	8894.68 ± 323.53	11.5539	0.0000
Fat (% of energy)	17.5 ± 1.9	28.0 ± 2.1	122.6558	0.0000
Carbohydrate (% of energy)	69.0 ± 2.8	53.1 ± 2.3	143.7258	0.0000
Protein (% of energy)	10.2 ± 1.2	15.2 ± 1.8	77.2145	0.0000
Alcohol (% of energy)	3.3 ± 0.7	3.7 ± 0.8	12.4623	0.0000
Carbohydrate (g/day)	368.67 ± 18.37	283.55 ± 16.49	113.2719	0.0000
Protein (g/day)	56.88 ± 2.68	81.64 ± 3.72	179.9916	0.0000
Animal (%)	15.1 ± 1.3	23.8 ± 1.6	140.1111	0.0000
Vegetable (%)	84.9 ± 2.7	76.2 ± 2.2	81.7987	0.0000
Total fat (g/day)	45.56 ± 1.63	72.38 ± 2.15	330.7780	0.0000
Saturated (g/day)	5.68 ± 0.74	12.76 ± 1.42	148.6934	0.0000
Monounsaturated (g/day)	10.81 ± 1.27	28.85 ± 1.87	266.4685	0.0000
Polyunsaturated (g/day)	23.38 ± 1.16	26.46 ± 1.37	56.8864	0.0000
Dietary cholesterol (mg/day)	176.82 ± 102.25	197.44 ± 115.73	4.4207	0.0000
Total dietary fiber (g/day)	8.76 ± 3.59	6.69 ± 2.37	15.6576	0.0000
Sodium intake (g/day)	8.83 ± 3.78	6.47 ± 2.71	16.5498	0.0000

Prevalence of hyperlipidemia in different villages between Hei Yi Zhuang and Han

There were significant differences of the increased rates of TC, TG, HDL-C, LDL-C, Apo B and the ratio of Apo A1 to Apo B in seven villages of Hei Yi Zhuang (P < 0.05–0.001) and TC, HDL-C, LDL–C and Apo B in nine villages of Han (P < 0.05–0.001) (Table 4).

Discussion

Cholesterol and TG are the main components of blood lipids. An excessive source (including intake from food or synthesis in the liver) or a catabolic obstacle, or both, can increase serum levels. The present study shows that the prevalence of hyperlipidemia in Hei Yi Zhuang is significantly lower than that in Han. The effects of genetic factors [15] as well as environmental factors, such as socio-economic milieu [16], dietary constituents [6, 17], alcohol consumption [18], cigarette smoking [18, 19], physical activity [20], and different races [17, 21] on the prevalence of hyperlipidemia have been clearly documented. Although Hei Yi Zhuang and Han live in the same region, the risk factors as mentioned above might be dissimilar. The great majority of Hei Yi Zhuang people live in mountaneous areas. The staple food is corn gruel or corn tortillas. On ordinary days, they are vegetarians. Corn wine and rum comprise about 95% of their beverages. The Han population mostly takes rice as the staple food. The standard of living in Han is higher than that in Hei Yi Zhuang. The intake of animal fat in Han is higher than that in Hei Yi Zhuang, and body weight and BMI are also significantly higher than those in Hei Yi Zhuang. For nearly 50 years it has been widely accepted that high-fat diets, particularly those that contain large quantities of saturated fatty acids, raise blood cholesterol concentrations and predispose individuals to cardiovascular disease [22]. In addition, the other major cause of different lipid levels between Hei Yi Zhuang and Han may relate to the excessive intake of corn in the former. Corn contains abundant dietary fiber and high-quality plant protein [23]. Consumption of dietary fiber, specifically the soluble type, such as pectins and guar gum, can result in a decrease of serum cholesterol levels in healthy and hyperlipidemic subjects [24]. Plant protein might raise the serum levels of HDL-C, and promote the transportation and excretion of free cholesterol. Corn oil is a kind of edible oil that is enriched with polyunsaturated fatty acid and monounsaturated fatty acids [25], and it is mostly used for cooking by Hei Yi Zhuang. A great deal of research has indicated that suitable intakes of polyunsaturated and monounsaturated fatty acids can lower the serum levels of cholesterol and LDL-C [25, 26]. A potential beneficial effect of dietary monounsaturated fatty acid on HDL-C has been suggested [27]. Corn oil could increase the ratio of HDL-C to TC and decrease the ratio of LDL-C to HDL-C [25].

Table 2

Effects of demographic, dietary and lifestyle characteristics on the prevalence of hyperlipidemia between Hei Yi Zhuang and Han

Characteristics	n	TC > 5.17 mmol/l	TG > 1.70 mmol/l	HDL-C > 1.81 mmol/l	LDL-C > 3.20 mmol/l	Apo A1 < 1.0 g/l	Apo B > 1.14 g/l	Apo A1/B > 2.50
Hei Yi Zhuang	1166	275 (23.6)	144 (12.3)	824 (70.7)	111 (9.5)	10 (0.9)	109 (9.3)	75 (6.4)
men	541	120 (22.2)	79 (14.6)	363 (67.1)	46 (8.5)	6 (1.1)	47 (8.7)	45 (8.3)
women	625	155 (24.8)	65 (10.4)∗	461 (73.8)∗	65 (10.4)	4 (0.6)	62 (9.9)	30 (4.8)∗
BMI ≤ 24 (kg/m2)	1039	233 (22.4)	115 (11.1)	737 (70.9)	89 (8.6)	9 (0.9)	87 (8.4)	72 (6.9)
BMI > 24 (kg/m2)	127	42 (33.1)∗∗	29 (22.8)∗∗∗	87 (68.5)	22 (17.3)∗∗	1 (0.8)	22 (17.3)∗∗	3 (2.4)∗
Normotensive	895	190 (21.2)	96 (10.7)	626 (69.9)	80 (8.9)	8 (0.9)	78 (8.7)	66 (7.4)
Hypertensive	271	85 (31.4)∗∗∗	48 (17.7)∗∗	198 (73.1)	31 (11.4)	2 (0.7)	31 (11.4)	9 (3.3)∗
No drinking	558	131 (23.5)	54 (9.7)	373 (66.8)	60 (10.8)	5 (0.9)	54 (9.7)	29 (5.2)
Alcohol intake	608	144 (23.7)	90 (14.8)∗∗	451 (74.2)∗∗	51 (8.4)	5 (0.8)	55 (9.0)	46 (7.6)
Nonsmoker	823	201 (24.4)	87 (10.6)	590 (71.7)	80 (9.7)	5 (0.6)	76 (9.2)	46 (5.6)
Cigarette smoking	343	74 (21.6)	57 (16.6)∗∗	234 (68.2)	31 (9.0)	5 (1.5)	33 (9.6)	29 (8.5)
< 20	98	8 (8.2)	11 (11.2)	38 (38.8)	2 (2.0)	3 (3.1)	3 (3.1)	10 (10.2)
20–29	156	27 (17.3)	21 (13.5)	101 (64.7)	13 (8.3)	3 (1.9)	8 (5.1)	13 (8.3)
30–39	255	50 (19.6)	25 (9.8)	191 (74.9)	19 (7.5)	2 (0.8)	17 (6.7)	20 (7.8)
40–49	177	42 (23.7)	21 (11.9)	131 (74.0)	13 (7.3)	1 (0.6)	14 (7.9)	18 (10.2)
50–59	196	61 (31.1)	24 (12.2)	153 (78.1)	30 (15.3)	0	30 (15.3)	8 (4.1)
60–69	196	55 (28.1)	27 (13.8)	148 (75.5)	20 (10.2)	1 (0.5)	23 (11.7)	5 (2.6)
70–79	76	26 (34.2)	12 (15.8)	44 (57.9)	10 (13.2)	1 (1.3)	10 (13.2)	1 (1.3)
≥ 80	12	6 (50.0)	3 (25.0)	8 (66.7)	4 (33.3)	0	4 (33.3)	0
χ2 for 8 age subgroups	−	36.348	4.833	65.835	25.652	9.133	29.423	19.040
P for 8 age subgroups	−	< 0.001	> 0.05	< 0.001	< 0.001	> 0.05	< 0.001	< 0.01
Han nationality	1018	275 (27.0)	147 (14.4)	646 (63.5)c	137 (13.5)c	9 (0.9)	147 (14.4)c	24 (2.4)c
men	426	113 (26.5)	67 (15.7)	245 (57.5)b	61 (14.3)b	7 (1.6)	61 (14.3)b	15 (3.5)b
women	592	162 (27.4)	80 (13.5)	401 (67.7)∗∗∗, a	76 (12.8)	2 (0.3)	86 (14.5)a	9 (1.5)∗, b
BMI ≤ 24 (kg/m2)	808	183 (22.6)	98 (12.1)	525 (65.0)b	90 (11.1)	8 (1.0)	93 (11.5)a	22 (2.7)c
BMI > 24 (kg/m2)	210	92 (43.8)∗∗∗	49 (23.3)∗∗∗	121 (576)∗, a	47 (22.4)∗∗∗	1 (0.5)	54 (25.7)∗∗∗	2 (1.0)
Normotensive	855	203 (23.7)	108 (12.6)	540 (63.2)b	102 (11.9)a	7 (0.8)	103 (12.0)a	20 (2.3)c
Hypertensive	163	72 (44.2)∗∗∗  b	39 (23.9)∗∗∗	106 (65.0)	35 (21.5)∗∗∗  b	2 (1.2)	44 (27.0)∗∗∗  c	4 (2.5)
No drinking	550	129 (23.5)	67 (12.2)	329 (59.8)a	72 (13.1)	5 (0.9)	69 (12.5)	11 (2.0)b
Alcohol intake	468	146 (31.2)∗∗, b	80 (17.1)∗	317 (67.7)∗∗, a	65 (13.9)b	4 (0.9)	78 (16.7)c	13 (2.8)
Nonsmoker	742	202 (27.2)	104 (14.0)a	484 (65.2)b	101 (13.6)a	4 (0.5)	108 (14.6)b	12 (1.6)c
Cigarette smoking	276	73 (26.4)	43 (15.6)	162 (58.7)a	36 (13.0)	5 (1.8)	39 (14.1)	12 (4.3)∗, a
< 20	85	7 (8.2)	13 (15.3)	41 (48.2)	4 (4.7)	2 (2.4)	3 (3.5)	4 (4.7)
20–29	183	32 (17.5)	15 (8.2)	104 (56.8)	18 (9.8)	3 (1.6)	13 (7.1)	2 (1.1)b
30–39	230	50 (21.7)	32 (13.9)	146 (63.5)b	23 (10.0)	1 (0.4)	25 (10.9)	8 (3.5)a
40–49	173	56 (32.4)	27 (15.6)	110 (63.6)a	27 (15.6)a	1 (0.6)	27 (15.6)a	4 (2.3)b
50–59	149	59 (39.6)	25 (16.8)	109 (73.2)	32 (21.5)	1 (0.7)	35 (23.5)	4 (2.7)
60–69	117	45 (38.5)	18 (15.4)	83 (70.9)	25 (21.4)b	0	29 (24.8)b	1 (0.9)
70–79	73	24 (32.9)	17 (23.3)	49 (67.1)	7 (9.6)	1 (1.4)	13 (17.8)	1 (1.4)
≥ 80	8	2 (25.0)	0	4 (50.0)	1 (12.5)	0	2 (25.0)	0
χ2 for 8 age subgroups	−	50.423	12.786	21.875	26.154	5.388	40.132	6.284
P for 8 age subgroups	−	< 0.001	> 0.05	< 0.01	< 0.001	> 0.05	< 0.001	> 0.05

TC, total cholesterol; TG, triglyceride; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; Apo A1, apolipoprotein A1; Apo B, apolipoprotein B; Apo A1/Apo B, the ratio of apolipoprotein A1 to apolipoprotein B; BMI, body mass index;

∗ P < 0.05,

∗∗P < 0.01 and

∗∗∗P < 0.001 in comparison with men, BMI ≤ 24 (kg/m²), normotensive, no drinking, or nonsmoker of same nationality;

^a  P < 0.05,

^b  P < 0.01 and

^c  P < 0.001 in comparison with same subgroup of Hei Yi Zhuang.

Strict intra-nationality marriages have taken place from time immemorial in this population. Namely, only partners who are both Hei Yi Zhuang can marry, and individuals can not intermarry with members of the other groups of Zhuang or other nationalities [8]. Therefore, the hereditary characteristics and gene phenotypes of lipids in Hei Yi Zhuang may be different from those in Han, but this still needs to be determined.

Currently it is thought that androgens induce disadvantageous effects on lipids, whereas estrogens are held to have opposite effects [28]. In the present study, we show that the increased rates of TG and the ratio of Apo A1 to Apo B in Hei Yi Zhuang are higher in males than in females, but the increased rate of HDL-C is lower in males than in females; the increased rate of the ratio of Apo A1 to Apo B in Han is higher in males than in females, but the increased rate of HDL-C is also lower in males than in females. However, there is no significant correlation between the prevalence of hyperlipidemia and sex in both Hei Yi Zhuang and Han. The reason for this discrepancy is unclear.

Epidemiological studies have provided abundant evidence that lipid levels are closely related to age [29]. In the present study, we show that the increased rates of TC, HDL-C, LDL-C, Apo B and the ratio of Apo A1 to Apo B in Hei Yi Zhuang and TC, HDL-C, LDL-C and Apo B in Han increase with increasing age. The prevalence of hyperlipidemia is positively correlated with age in both Hei Yi Zhuang and Han. This is in agreement with previous studies. The exact mechanisms of age on the prevalence of hyperlipidemia are not known. It may due, in part, to the hereditary characteristics and aging of the population.

Table 3

The risk factors of the prevalence of hyperlipidemia between Hei Yi Zhuang and Han

Populations	Risk factors	Regression coefficient	Standard error	Wald	P	OR
Han plus Hei	Age (years)	0.457	0.043	150.156	0.000	1.577
	Body mass index (kg/m2)	0.442	0.128	12.132	0.000	1.556
	Blood pressure (mmHg)	0.571	0.134	9.986	0.002	1.223
	Alcohol consumption (g/day)	0.198	0.064	8.388	0.004	1.236
	Nationality	0.398	0.127	11.042	0.001	1.496
Han nationality	Age (years)	0.455	0.058	61.458	0.000	1.568
	Body mass index (kg/m2)	0.624	0.198	10.345	0.001	1.871
	Blood pressure (mmHg)	0.543	0.207	7.221	0.008	1.734
	Alcohol consumption (g/day)	0.273	0.106	7.604	0.006	1.312
Hei Yi Zhuang	Age (years)	0.453	0.049	92.314	0.000	1.565
	Body mass index (kg/m2)	0.422	0.223	3.968	0.043	1.526
	Blood pressure (mmHg)	0.628	0.182	12.239	0.000	1.846

Wald, the value of the Wald test; OR, odds ratio.

Table 4

The prevalence of hyperlipidemia in different villages between Hei Yi Zhuang and Han [n (%)]

Villages	n	TC > 5.17 mmol/l	TG > 1.70 mmol/l	HDL-C > 1.81 mmol/l	LDL-C > 3.20 mmol/l	Apo A1 < 1.0 g/l	Apo B > 1.14 g/l	Apo A1/Apo B > 2.50
Hei Yi Zhuang
Longhua	343	76 (22.2)	48 (14.0)	221 (64.4)	29 (8.5)	2 (0.6)	30 (8.7)	18 (5.2)
Gonghe	109	38 (34.9)	23 (21.1)	91 (83.5)	10 (9.2)	1 (0.9)	8 (7.3)	6 (5.5)
Guotao	182	23 (12.6)	13 (7.1)	140 (76.9)	7 (3.8)	2 (1.1)	5 (2.7)	13 (7.1)
Tuanjie	201	56 (27.9)	24 (11.9)	139 (69.2)	30 (14.9)	2 (1.0)	30 (14.9)	7 (3.5)
Yongan	141	29 (20.6)	9 (6.4)	104 (73.8)	11 (7.8)	1 (0.7)	11 (7.8)	18 (12.8)
Nianyan	80	15 (18.8)	10 (12.5)	48 (60.0)	9 (11.3)	0	12 (15.0)	6 (7.5)
Shanhe	110	38 (34.5)	17 (15.5)	81 (73.6)	15 (13.6)	2 (1.8)	13 (11.8)	7 (6.4)
χ2	−	31.304	18.777	24.244	17.013	2.400	21.607	13.564
P	−	< 0.001	< 0.01	< 0.001	< 0.01	> 0.05	< 0.01	< 0.05
Han nationality
Yongle	150	56 (37.3)	27 (18.0)	92 (61.3)	26 (17.3)	0	22 (14.7)	3 (2.0)
Zhemiao	78	27 (34.6)	17 (21.8)	37 (47.4)	18 (23.1)	1 (1.3)	24 (30.8)	0
Dala	72	19 (26.4)	11 (15.3)	49 (68.1)	5 (6.9)	0	8 (11.1)	0
Xiaoguola	149	28 (18.8)	18 (12.1)	104 (69.8)	9 (6.0)	1 (0.7)	15 (10.1)	4 (2.7)
Longdi	184	48 (26.1)	20 (10.9)	122 (66.3)	26 (14.1)	2 (1.1)	23 (12.5)	7 (3.8)
Nianyan	70	12 (17.1)	7 (10.0)	47 (67.1)	9 (12.9)	0	6 (8.6)	1 (1.4)
Pohe	13	8 (61.5)	1 (7.7)	10 (76.9)	3 (23.1)	0	5 (38.5)	0
Chaoqun	86	21 (24.4)	9 (10.5)	49 (57.0)	12 (14.0)	2 (2.3)	11 (12.8)	2 (2.3)
Longping	216	56 (25.9)	37 (17.1)	136 (63.0)	29 (13.4)	3 (1.4)	33 (15.3)	7 (3.2)
χ2	−	27.333	11.525	15.816	18.937	5.693	28.688	6.756
P	−	< 0.001	> 0.05	< 0.05	< 0.05	> 0.05	< 0.001	> 0.05

TC, total cholesterol; TG, triglyceride; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; Apo A1, apolipoprotein A1; Apo B, apolipoprotein B; Apo A1/Apo B, the ratio of apolipoprotein A1 to apolipoprotein B.

The relationship between obesity and dyslipidemia has been clearly documented [30]. Obesity not only increases the prevalence of hyperlipidemia, but is also associated directly with diabetes, high blood pressure and coronary artery disease. The current study shows that the increased rates of TC, TG, LDL-C and Apo B in subjects with BMI > 24 kg/m² are higher than those in subjects with BMI ≤ 24 kg/m² in both Hei Yi Zhuang and Han. The prevalence of hyperlipidemia is also positively correlated with BMI in both ethnic groups. This is in agreement with previous studies [30, 31]. Dyslipidemia in obesity may result from insulin resistance [32]. The liver is an important target organ of insulin effects. Insulin resistance can lower the repression by insulin of the concentrations of plasma free fatty acids, increase the plasma levels of free fatty acids, promote free fatty acids transport into the liver, and stimulate the synthesis and release of very low-density lipoprotein (VLDL) in the liver. At the same time, insulin resistance can also lower the activity of lipoprotein lipase, reducing the metabolism of VLDL, and increasing the levels of plasma VLDL.

The association between serum lipids and blood pressure is not well known. Studies have shown that the levels of triglyceride, VLDL cholesterol and Apo E were significantly higher and the levels of Apo A1, Apo AII and Apo CII significantly lower in untreated hypertensives than those in controls [33]. TC and non-HDL-C levels increased significantly with increasing systolic or diastolic blood pressure in both sexes [34]. Some authors thought that this relation may be a kind of random phenomenon [35], but our study reveals that the increased rates of TC and TG in subjects with hypertension are higher than those in subjects without hypertension in Hei Yi Zhuang, and the increased rates of TC, TG, LDL-C and Apo B in hypertensives are higher than those in normotensives in Han. The prevalence of hyperlipidemia is also positively correlated with blood pressure in both Hei Yi Zhuang and Han. We suggest that there may be a biological interrelation between blood pressure and lipids [36].

The effects of alcohol consumption [18] and cigarette smoking [18, 19] on plasma or serum lipid concentrations and their effects on cardiovascular health have been studied extensively. Low amounts of alcohol, when taken on a regular basis, have been shown to protect against cardiovascular disease and death [37], whereas heavy drinking and cigarette smoking constitute a severe risk condition. In the present study, we show that the increased rates of TG and HDL-C in Hei Yi Zhuang are higher in drinkers than in nondrinkers, and the increased rate of TG is higher in smokers than in nonsmokers; also the increased rates of TC, TG and HDL-C in Han are higher in drinkers than in nondrinkers; but there is no significant correlation between the prevalence of hyperlipidemia and alcohol consumption or cigarette smoking in either Hei Yi Zhuang or Han, suggesting that alcohol consumption and cigarette smoking may not be independent risk factors for hyperlipidemia in these populations.

In the present study, we also show that there are significant differences of the increased rates of TC, TG, HDL-C, LDL-C, Apo B and the ratio of Apo A1 to Apo B in seven villages of Hei Yi Zhuang and TC, HDL-C, LDL-C and Apo B in nine villages of Han. The reason for these differences is not well understood.

In conclusion, the present study indicates that the prevalence of hyperlipidemia is significantly lower in Hei Yi Zhuang than in Han. The prevalence of hyperlipidemia is positively correlated with age, BMI and blood pressure in Hei Yi Zhuang, whereas it is positively associated with age, BMI, blood pressure and alcohol consumption in Han, which might result from different demographic characteristics, dietary habits and other lifestyle factors.

Author notes

Sponsorship: This study was supported by the National Natural Science Foundation of China (No. 30360038).