Abstract

There is an obvious lack of validated norms for elderly persons aged 85 and older for the large majority of the neuropsychological tests used in clinical practice. Yet this range of “oldest-old” individuals drastically increases worldwide and is the more likely to develop dementia. Providing clinicians validated and updated norms to accurately evaluate cognitive functioning in this population is an important issue in geriatrics. This study provides normative scores for 7 neuropsychological tests commonly used in clinical practice. Data were collected in a sample of 283 subjects aged 85 and older, included in the PAQUID study, a population-based cohort conducted in France. Normative scores were calculated according to 2 age ranges and 2 educational levels, and are presented in percentiles. The norms provided in the present study involve 7 tests that are widely used in the neuropsychological assessment of geriatrics populations and should be of help for clinicians.

Introduction

The proportion of individuals aged 80 and above often called “oldest old” is increasing dramatically worldwide with huge repercussions on public health. In 2013, 14% of elderly population is 80 and older, and this proportion is expected to reach 19% in 2050 and 28% in 2100 (United Nations, Department of Economic and Social Affairs, Population Division, 2013). By the end of the century, there could be 830 million people aged 80 and over. In developed countries, the proportion of oldest old will peak in 2050 with over 10% of the whole population (United Nations, Department of Economic and Social Affairs, Population Division, 2013).

With age being the strongest risk factor of dementia among the elderly people (e.g., Corrada, Brookmeyer, Paganini-Hill, Berlau, & Kawas, 2010; Helmer, Pasquier, & Dartigues, 2006), the oldest old are the more likely to develop Alzheimer's disease. Indeed, the prevalence of dementia is over 30% in the 85 and older age group (Helmer et al., 2006). Furthermore, beyond 80, four of five demented persons do not have access to recommended diagnosis procedures (Helmer et al., 2008). Such diagnosis procedures involve a neuropsychological assessment. However, there is an obvious lack of tools and norms adapted to this specific population. Most of the studies having computed normative scores for elderly population either excluded persons above 85 (e.g., Grigoletto, Zappala, Anderson, & Lebowitz, 1999; Ostrosky-Solis, Ardila, & Rosselli, 1999; Rossetti, Lacritz, Cullum, & Weiner, 2011) or presented a weak number of participants in that age category (e.g., Bleecker, Bolla-Wilson, Kawas, & Agnew, 1988; Ishizaki et al., 1998; Lechevallier-Michel, Frabrigoule, Lafont, Letenneur, & Dartigues, 2004).

The lack of normative data specifically set up for oldest-old population leads clinicians to use either norms established in samples of younger elderly or obsolete norms provided by dated publications. With the strong effect of age on cognitive performances, the use of norms for elderly individuals of younger age would lead to overdiagnose cognitive impairment. On the other hand, the use of obsolete norms should probably lead to underdiagnose dementia. Indeed, several studies have shown an improvement of general cognitive capacities across generations (Dickinson & Hiscock, 2011; Lynn & Hampson, 1986; Trahan, Stuebing, Fletcher, & Hiscock, 2014), which means that at the same age, elderly individuals have better performances nowadays than they used to have several decades ago due to general improvement of environmental conditions. This phenomenon is known as “cohort effect” or “Flynn effect.”

Scarce studies have provided norms for the oldest-old population. In the 90+ Study, authors have established normative data for various neuropsychological tests such as the Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1975) and the California Verbal Learning Test-II Short Form (Delis, Kramer, Kaplan, & Ober, 2000; Whittle et al., 2007). In this study, norms were based on a particular population. The participants were residents of “Leisure World,” a retirement community in California. Leisure world's population is generally a highly educated population with high socioeconomic status. In the Georgia Centenarian Study, Miller and colleagues (2010) and Rahman-Filipiak and colleagues (2014) provided norms for the MMSE (Folstein et al., 1975), the Severe Impairment Battery (Panisset, Roudier, Saxton, & Boller, 1994), the Behavioral Dyscontrol Scale (Grigsby & Kaye, 1996), and the Fuld Object Memory Evaluation (Fuld, 1981) from a sample of centenarians and octogenarians. However, in this study, participants with dementia were not excluded from the study sample. Therefore, the scores, including both normal and pathological scores, show a huge variability. The Cambridge City over-75s Cohort (Dufouil et al. 2000) provided MMSE (Folstein et al., 1975) norms in the oldest old. This study included participants aged 75 and older followed-up for 9 years who were geographically and socially representative of general practitioners' patients of Cambridge area. The study modeled the evolution of MMSE scores across three age categories including the category of 85 and older. Finally, based on a sample of cognitively normal volunteers recruited in Alzheimer's Disease Centers, Weintraub and colleagues (2009) provided demographically calibrated data for several tests from the Uniform Data Set.

Therefore, even if these studies have provided norms, the results can be hardly generalized due to the sampling selection. The PAQUID cohort is a French prospective population-based study started in 1989. With its still ongoing follow-up, the sample now consists exclusively of participants aged 85 and older. Therefore, we took advantage of the PAQUID cohort to compute norms on several neuropsychological tests for the oldest old.

The aim of this study is to establish norms for seven commonly used tests providing various measures of global cognitive efficiency, visual working memory, verbal fluency, psychomotor speed, selective attention, episodic memory, and abstract verbal reasoning. The tests are the following: MMSE, Benton Visual Retention Test (BVRT), Isaacs' Set Test (IST), Digit Symbol Substitution Test (DSST), Zazzo's Cancellation Task (short 8-line version) (ZCT), Wechsler Paired-Associates Test (WPAT), and Wechsler Similarities Test (WST). The article presents the normative data according to age and education. The indicators reported are the 5th, 10th, 25th, 50th, and 75th percentiles.

Methods

Sample

The PAQUID study (Personnes âgées QUID) is a large French prospective population-based study on functional and brain aging conducted in 75 districts of southwestern France. The baseline sample consisted of 3,777 participants living at home and aged 65 and older. The sample was representative of the general population in terms of age and gender. The detailed methodology has been previously published (Dartigues et al., 1991).

After the baseline visit, the participants had follow-up visits every 2 or 3 years performed at home by trained psychologists. The interviews consisted of a standardized questionnaire including sociodemographics, living conditions, social network, subjective and objective health measures, personal medical history, and sensory deficits. Functional restriction was evaluated by Instrumental Activities of Daily Living (Lawton & Brody, 1969) scales. Depressive symptomatology was assessed by the Center for Epidemiologic Studies Depression Scale (Fuhrer & Rouillon, 1989).

Following the interview, the psychologists completed the DSM-III-R criteria (American Psychiatric Association, 1987) for dementia. Participants suspected to have dementia were visited by a geriatrician or neurologist who confirmed the diagnosis and specified the etiology according to current international diagnostic criteria.

At the 20-year follow-up, the sample was composed of 505 participants. For the present study, participants diagnosed as suffering dementia (n = 176), those with major visual deficits (n = 4), those with major hearing impairment (n = 28), those who were institutionalized (n = 14), and those confined to bed (n = 4) were excluded from the study sample. Finally, the study sample was of 283 participants (see Fig. 1).

Fig. 1.

Flow chart: Study sample for the norms of the different tests (MMSE, BVRT, IST, DSST, ZCT, WPAT, and WST) in the PAQUID cohort at 20-year follow-up. Note: MMSE = Mini-Mental State Examination; BVRT = Benton Visual Retention Test; IST = Isaacs’ Set Test; DSST = Digit Symbol Substitution Test; ZCT = Zazzo's Cancellation Task (short 8-line version); WPAT = Wechsler Paired-Associates Test; WST = Wechsler Similarities Test.

Fig. 1.

Flow chart: Study sample for the norms of the different tests (MMSE, BVRT, IST, DSST, ZCT, WPAT, and WST) in the PAQUID cohort at 20-year follow-up. Note: MMSE = Mini-Mental State Examination; BVRT = Benton Visual Retention Test; IST = Isaacs’ Set Test; DSST = Digit Symbol Substitution Test; ZCT = Zazzo's Cancellation Task (short 8-line version); WPAT = Wechsler Paired-Associates Test; WST = Wechsler Similarities Test.

Measures

The tests administered to participants at the 20-year follow-up of the PAQUID cohort were as follows.

Mini-Mental State Examination

MMSE is a standardized composite scale evaluating global cognitive performances. The 30 items explore orientation in time and space, immediate memory, delayed memory, mental calculation, language, and visual-constructive abilities. Total score varies from 0 to 30 (Folstein et al., 1975).

Benton Visual Retention Test

BVRT assesses visual working memory. The multichoice form (Form F) consists of 15 stimuli cards displaying geometric figures and 15 multichoice cards. A stimulus card is presented during 10 s. Then, the patient has to recognize the initial figure among a choice of four possibilities. One point is given for each correct identified figure. Total score varies from 0 to 15 (Benton, 1965).

Isaacs' Set Test

IST is a categorical verbal fluency test. It assesses the capacity to generate lists of words in four semantic categories (animals, fruits, colors, and cities) in 60 s. According to the original version, the maximum number of words recorded was limited to 10 by category. A massive ceiling effect was observed in normal subjects. For this reason, in the PAQUID cohort, all the words were recorded during 1 min. The score consists of the sum of the words generated at 15 and 60 s for the four categories (Isaacs & Kennie, 1973).

Digit Symbol Substitution Test

DSST is a subtest of the WAIS scale. A table of nine digits corresponding with nine symbols is presented. Under this table, empty boxes displaying digits have to be completed according to the model. The score consists of the number of boxes correctly completed in 90 s (Wechsler, 1981).

Zazzo's Cancellation Task (short 8-line version)

ZCT is a cancellation task consisting of 40 lines of target and distractor signs. The target sign is presented at the top of the page. The subject is asked to cross out all the target signs as fast as possible. The shortened version displaying only the first eight lines was used in this study (Amieva, Rouch-Leroyer, Letenneur, Dartigues, & Fabrigoule, 2004). Scores are the number of correctly crossed out targets (maximum: 29) and the time spent to complete the task (Zazzo, 1974).

Wechsler Paired-Associates Test

WPAT is a subtest of the Wechsler memory scale III. It involves verbal episodic memory. The examiner reads aloud 10 word pairs. After reading the list, the first word of each pair is given. The subject is asked to provide the second word. Six word pairs are easy to associate (e.g., north–south) and four are more difficult (e.g., coleslaw–feather). 0.5 point is attributed to each easy pair retrieved and 1 point is attributed to the more difficult ones. Three successive trials are performed; each of them varies from 0 to 7 (Wechsler, 1945).

Wechsler Similarities Test

WST is an abstract verbal thinking test. The subject is asked to explain in what way two things are alike. Only the first five pairs were administered. Two points are given for an abstract generalization and one point for a common concrete attribute. The score varies from 0 to 10 (Wechsler, 1981).

The French validated versions of the tests have been used. These tests have previously shown their reliability in the cognitive follow-up of elderly participants (Amieva et al., 2005, 2008, 2014).

Data Analysis

Sociodemographic characteristics of the participants included in the study sample and those excluded were compared with t-tests and χ2 tests. The effect of age, gender, and education was assessed with a linear regression analysis. The performances were significantly different according to education and age. No effect of gender was found after adjusting on age and education. Two age groups were set up according to the median age (85–88; 88 and above). Two educational level groups were considered: persons without any diploma or persons with the “Certificat d'Etudes Primaires” (CEP; equivalent to primary school diploma) and higher degree. This cutoff was selected for three reasons. Firstly, in France, the oldest-old population grew up in the context of the Second World War and is mostly low educated. Secondly, the study by Letenneur and colleagues (1999) showed that the CEP level was the more discriminant educational level cutoff in this cohort regarding the risk of developing dementia. Finally, the CEP allowed stratifying our study sample in two groups of relatively similar size (n = 178 for ≤CEP vs. n = 105 for >CEP). Therefore, the sample was stratified according to age and education for all the tests except for the WST for which the effect of age was not statistically significant.

The percentiles have two main advantages: they are adapted for data that are not normally distributed and offers the opportunity to situate a subject's performance compared with a large range of normal individuals. The indicators reported are the 5th, 10th, 25th, 50th, and 75th percentiles stratified on the sample according to the associated factors found for each measure/test. Statistical analyses were performed using Statistical Analysis System (SAS) version 9.3® (SAS Institute, Cary, NC).

Results

Norms have been calculated on a sample of 283 participants. Included subjects presented sociodemographic differences with excluded subjects. They were significantly younger (t = 6.1, p < .0001), had a higher education level (χ2 = 15.9, p < .0001), were less dependent (χ2 = 90.2, p < .0001), more frequently men (χ2 = 8.3, p = .0040), and had a higher mean MMSE score (t = 14.3, p < .0001; Table 1).

Table 1.

Sociodemographic and health-related characteristics of the two groups (n = 283)

Demographic and health-related variables Population included Population excluded Comparison 
(N = 283) (N = 222) p2/t-tests) 
Age (years), mean (SD89.2 (3.1) 91.1 (3.9) <.0001 
Min.–max. 85.2—100.6 85.9—102.8  
Age (years), n (%) 
 <88 132 (46.6) 48 (21.6) <.0001 
 ≥88 151 (53.4) 174 (78.4) 
 Gender, n (%), women 179 (63.3) 167 (75.2) .0040 
Educational level, n (%) 
 ≤CEP 178 (62.9) 176 (79.3) <.0001 
 >CEP 105 (37.1) 46 (20.7) 
Depressive symptomatology, n (%) (MD = 141) 21 (8.1) 11 (10.5) .4698 
MMSE score/30, mean (SD26.7 (2.5) (n = 279) 19.7 (6.4) (n = 181) <.0001 
IADL dependency, n (%) 155 (54.8) 206 (93.2) <.0001 
Subjective health, n (%) (MD = 55) 
 Good 136 (48.1) 72 (43.1) .5906 
 Moderate 108 (38.1) 69 (41.3) 
 Poor 39 (13.8) 26 (15.6) 
Demographic and health-related variables Population included Population excluded Comparison 
(N = 283) (N = 222) p2/t-tests) 
Age (years), mean (SD89.2 (3.1) 91.1 (3.9) <.0001 
Min.–max. 85.2—100.6 85.9—102.8  
Age (years), n (%) 
 <88 132 (46.6) 48 (21.6) <.0001 
 ≥88 151 (53.4) 174 (78.4) 
 Gender, n (%), women 179 (63.3) 167 (75.2) .0040 
Educational level, n (%) 
 ≤CEP 178 (62.9) 176 (79.3) <.0001 
 >CEP 105 (37.1) 46 (20.7) 
Depressive symptomatology, n (%) (MD = 141) 21 (8.1) 11 (10.5) .4698 
MMSE score/30, mean (SD26.7 (2.5) (n = 279) 19.7 (6.4) (n = 181) <.0001 
IADL dependency, n (%) 155 (54.8) 206 (93.2) <.0001 
Subjective health, n (%) (MD = 55) 
 Good 136 (48.1) 72 (43.1) .5906 
 Moderate 108 (38.1) 69 (41.3) 
 Poor 39 (13.8) 26 (15.6) 

Note: CEP = Certificat d'Etudes Primaires (Primary school diploma); MD = missing data; SD = standard deviation; IADL = instrumental activities of daily living; MMSE = Mini-Mental State Examination.

The mean age of the study sample was 89.2 years (standard deviation [SD] = 3.1), 46.6% were in the age range of 85–88 and 53.4% were older, 63.3% were women, 62.9% had low education level (≤CEP), 48.1% of participants reported good health, 38.1% reported moderately good health, and 13.8% reported poor health. The MMSE mean score was 26.7 (SD = 2.5). Table 2 displays the characteristics of the two age groups.

Table 2.

Sociodemographic and health-related characteristics of the two age groups

Demographic and health-related variables Age group <88 years (N = 132) Age group ≥88 years (N = 151) 
Age, mean (SD86.9 (0.6) 91.1 (3.0) 
Gender, n (%), women 74 (56.0) 105 (69.5) 
Educational level, n (%) 
 ≤CEP 75 (56.8) 103 (68.2) 
 >CEP 57 (43.1) 48 (31.8) 
Depressive symptomatology, n (%) 9 (7.4) (MD = 11) 12 (8.7) (MD = 13) 
MMSE score/30, mean (SD27.1 (2.3) 26.3 (2.6) 
IADL dependency, n (%) 55 (41.7) 100 (66.2) 
Subjective health, n (%) 
 Good 65 (49.2) 71 (47.0) 
 Moderate 48 (36.4) 60 (39.7) 
 Poor 19 (14.4) 20 (13.2) 
Demographic and health-related variables Age group <88 years (N = 132) Age group ≥88 years (N = 151) 
Age, mean (SD86.9 (0.6) 91.1 (3.0) 
Gender, n (%), women 74 (56.0) 105 (69.5) 
Educational level, n (%) 
 ≤CEP 75 (56.8) 103 (68.2) 
 >CEP 57 (43.1) 48 (31.8) 
Depressive symptomatology, n (%) 9 (7.4) (MD = 11) 12 (8.7) (MD = 13) 
MMSE score/30, mean (SD27.1 (2.3) 26.3 (2.6) 
IADL dependency, n (%) 55 (41.7) 100 (66.2) 
Subjective health, n (%) 
 Good 65 (49.2) 71 (47.0) 
 Moderate 48 (36.4) 60 (39.7) 
 Poor 19 (14.4) 20 (13.2) 

Note: CEP = Certificat d'Etudes Primaires (Primary school diploma); MD = missing data; SD = standard deviation; IADL = instrumental activities of daily living; MMSE = Mini-Mental State Examination.

For each test, the participants with missing data have been excluded. Normative data for the sample are presented subsequently.

Effect of age and education was significant for MMSE, BVRT, IST-15 s and IST-60 s, DSST, ZCT, and WPAT. No effect of age was observed for the WST. Normative scores are presented in Tables 3 and 4.

Table 3.

Normative scores for the MMSE by age and educational level

Age groups Educational level
 
Total 
≤CEP >CEP 
85–88 years 
N 74 57 131 
  5% 22 24 22 
  10% 23 26 24 
  25% 25 27 26 
  50% 27 28 28 
  75% 28 30 29 
≥88 years 
N 100 48 148 
  5% 22 23 22 
  10% 23 25 23 
  25% 24 26 25 
  50% 26 27 27 
  75% 28 29 29 
Age groups Educational level
 
Total 
≤CEP >CEP 
85–88 years 
N 74 57 131 
  5% 22 24 22 
  10% 23 26 24 
  25% 25 27 26 
  50% 27 28 28 
  75% 28 30 29 
≥88 years 
N 100 48 148 
  5% 22 23 22 
  10% 23 25 23 
  25% 24 26 25 
  50% 26 27 27 
  75% 28 29 29 

Note: CEP = Certificat d'Etudes Primaires (Primary school diploma); MMSE = Mini-Mental State Examination.

Table 4.

Normative scores for the neuropsychological tests by age and educational level

Age groups Benton Visual Retention Test
 
Isaacs' Set Test (15 s)
 
Isaacs' Set Test (60 s)
 
Digit Symbol Substitution Test
 
Zazzo (number of crossed out targets)
 
Zazzo (time to complete test)
 
Wechsler Paired-Associates Test
 
Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total 
≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP 
85–88 years 
N 68 55 123 74 56 130 71 55 126 58 51 109 66 54 120 66 54 120 57 53 110 
  5% 14 18 16 31 45 34 20 11 23 27 24 60 49 53 11 19 15 
  10% 10 18 23 18 34 50 36 11 21 14 25 27 26 66 55 57 16 21 18 
  25% 11 10 21 26 22 39 55 45 18 25 21 27 28 27 79 66 72 19 23 22 
  50% 11 12 12 23 29 27 52 65 59 22 31 26 28 29 28 103 80 88 24 26 25 
  75% 13 13 13 30 32 31 63 75 68 27 37 33 29 29 29 126 104 119 27 28 28 
≥88 years 
N 91 44 135 95 48 143 94 47 141 67 43 110 77 45 122 77 45 122 76 44 120 
  5% 10 15 15 16 32 35 32 10 18 10 21 26 23 58 64 61 11 14 12 
  10% 10 17 19 18 35 40 35 11 18 11 23 26 25 65 69 67 14 17 14 
  25% 11 20 21 21 42 45 44 15 24 18 26 27 27 82 77 80 19 19 19 
  50% 10 12 11 23 23 23 52 57 53 20 27 22 28 28 28 106 87 97 22 23 22 
  75% 12 13 13 27 28 28 60 65 62 23 33 27 29 29 29 128 108 125 26 27 26 
Age groups Benton Visual Retention Test
 
Isaacs' Set Test (15 s)
 
Isaacs' Set Test (60 s)
 
Digit Symbol Substitution Test
 
Zazzo (number of crossed out targets)
 
Zazzo (time to complete test)
 
Wechsler Paired-Associates Test
 
Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total Educational level
 
Total 
≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP ≤CEP >CEP 
85–88 years 
N 68 55 123 74 56 130 71 55 126 58 51 109 66 54 120 66 54 120 57 53 110 
  5% 14 18 16 31 45 34 20 11 23 27 24 60 49 53 11 19 15 
  10% 10 18 23 18 34 50 36 11 21 14 25 27 26 66 55 57 16 21 18 
  25% 11 10 21 26 22 39 55 45 18 25 21 27 28 27 79 66 72 19 23 22 
  50% 11 12 12 23 29 27 52 65 59 22 31 26 28 29 28 103 80 88 24 26 25 
  75% 13 13 13 30 32 31 63 75 68 27 37 33 29 29 29 126 104 119 27 28 28 
≥88 years 
N 91 44 135 95 48 143 94 47 141 67 43 110 77 45 122 77 45 122 76 44 120 
  5% 10 15 15 16 32 35 32 10 18 10 21 26 23 58 64 61 11 14 12 
  10% 10 17 19 18 35 40 35 11 18 11 23 26 25 65 69 67 14 17 14 
  25% 11 20 21 21 42 45 44 15 24 18 26 27 27 82 77 80 19 19 19 
  50% 10 12 11 23 23 23 52 57 53 20 27 22 28 28 28 106 87 97 22 23 22 
  75% 12 13 13 27 28 28 60 65 62 23 33 27 29 29 29 128 108 125 26 27 26 

Note: CEP = Certificat d'Etudes Primaires (Primary school diploma).

Norms have been calculated according to age and education level. The 5th percentile corresponds to the threshold under which 5% of participants get the worst performances and the 75th percentile is the threshold above which 25% of participants get the best performances.

Discussion

Even though numerous normative data for elderly have been published, including for some of the tests considered in the present study (Acevedo et al., 2000; Crum, Anthony, Bassett, & Folstein, 1993; Lechevallier-Michel et al., 2004; Raoux, Le Goff, Auriacombe, Dartigues, & Amieva, 2010; Rullier et al., 2014; Tombaugh, 2004), there is an important lack of normative data specifically set up for oldest-old population. Thus, the aim of the present study was to provide norms for the MMSE, BVRT, IST, DSST, ZCT, WPAT, and WST for elderly participants aged 85 and older. These normative scores have been computed from a study sample composed of 283 elderly participants living in the community.

As expected, cognitive performances were lower in the oldest category of age and higher in the highest category of education for all the tests considered in this study except the Wechsler Similarities subtest for which no effect of age was found. This result is consistent with numerous previous findings showing that semantic knowledge along with crystallized intelligence is poorly affected by advancing age.

The main limit of this study relies on the sample size. The distribution of the 283 subjects in the different age and education level groups resulted in a limited number of participants in some categories. In addition, unlike the study of Lechevallier-Michel and colleagues (2004) conducted within the same cohort, in which three education level groups were provided, in our study, due to the sample size, only two education levels could be considered. Moreover, the normative scores provided in our study may not be appropriate for cross-cultural use. Before generalizing these data, their applicability in non-French population should be assessed. Nevertheless, this study also has several strengths among which its population-based design and the availability of dementia diagnosis give us the opportunity to exclude the participants with dementia from the study sample. Finally, the norms provided in the present study involve seven tests that are widely used in the neuropsychological assessment of geriatrics populations and should be of help for clinicians. A specific study should now be necessary to assess the cutoff scores that should be used in this population in order to draw practical recommendations in the screening of cognitive disorders in the oldest-old population.

Funding

This work was supported by grants from Fondation de France, Novartis Pharma, SCOR, Caisse Nationale d'Assurance Maladie, Conseil Général de la Dordogne, Conseil Général de la Gironde, Mutualité Sociale Agricole, Agrica and IPSEN.

Conflict of Interest

None declared.

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