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In traditional epidemiological studies, participants are likely motivated by perceived benefits, feelings of accomplishment, and belonging. No study has explored motives for participation in a Web-based cohort and the associated participant characteristics, although such information is useful for enhancing recruitment and improving cohort retention.
We aimed to evaluate the relationships between motives for participation and sociodemographic, health, and lifestyle characteristics of participants in the NutriNet-Santé Web-based cohort, designed to identify nutritional risk or protective factors for chronic diseases.
The motives for participation were assessed using a specifically developed questionnaire administered approximately 2 years after baseline. A total of 6352 completed the motives questionnaire (43.34%, 6352/15,000 randomly invited cohort participants). We studied the associations between motives (dependent variables) and individual characteristics with multivariate multinomial logistic regression models providing odds ratios and 95% confidence intervals.
In total, 46.45% (2951/6352) of participants reported that they would not have enrolled if the study had not been conducted on the Internet, whereas 28.75% (1826/6352) were not sure. Men (OR 1.21, 95% CI 1.04-1.42), individuals aged 26-35 years (OR 1.51, 95% CI 1.20-1.91), and obese participants (OR 1.30, 95% CI 1.02-1.65) were more inclined to be motivated by the Internet aspect. Compared with younger adults and managerial staff, individuals >55 years (OR 0.60, 95% CI 0.48-0.45) and employees/manual workers were less likely motivated by the Internet aspect (OR 0.77, 95% CI 0.63-0.92). Regarding reasons for participation, 61.37% (3898/6352) reported participating to help advance public health research on chronic disease prevention; 22.24% (1413/6352) to help advance nutrition-focused research; 6.89% (438/6352) in response to the call from the media, after being encouraged by a close friend/associate, or a medical provider. Individuals >45 years (vs younger participants) were more likely (OR 1.62, 95% CI 1.07-2.47), whereas overweight and obese participants (vs nonobese participants) were less likely to participate in the study for reasons related to helping public health research on chronic disease prevention (OR 0.72, 95% CI 0.58-0.89; OR 0.62, 95% CI 0.46-0.84; respectively). Exclusive public funding of the study was important for 67.02% (4257/6352) of the participants. Men (OR 1.37, 95% CI 1.17-1.61) and persons >55 years (OR 1.97, 95% CI 1.57-2.47) were more likely to consider the exclusive public funding as very important.
The use of the Internet, the willingness to help advance public health research, and the study being publicly funded were key motives for participating in the Web-based NutriNet-Santé cohort. These motives differed by sociodemographic profile and obesity, yet were not associated with lifestyle or health status. These findings can help improve the retention strategies in Web-based cohorts, particularly during decisive study periods when principal exposure information is collected.
The successful implementation of very large population-based cohort studies involving collection of comprehensive, high-quality dietary, lifestyle, and health data is both a priority and a challenge in nutritional epidemiology [
Yet Web-based prospective cohort studies are still in their infancy [
Voluntariness refers to the voluntary motivational nature of a person’s participation from the initial decision to participate through the course of the study, and is influenced by external and internal factors [
The NutriNet-Santé study was launched in May 2009 in France to investigate multiple facets of the relationship between nutrition and health along with determinants of dietary behavior [
Participants were part of the NutriNet-Santé Study, a large Web-based prospective observational cohort. It is implemented in a general population targeting Internet-using adult volunteers aged 18 years and older. The design, methods, and rationale have been described elsewhere [
Numerous scientific studies have highlighted the role of nutrition as a protective factor or a risk of many common diseases in France, as in all industrialized countries, such as cancer, cardiovascular diseases, obesity, type 2 diabetes, dyslipidemia, and hypertension. Nutrition is not the only determinant of these health problems. Indeed, genetic, biological, and environmental factors are involved in the onset of these diseases. To highlight the specific role of nutritional factors in health, the development of cohort studies with very large populations (group of participants followed for several years) is essential as they permit to accurately measure food intake, but also take into account other determinants, such as physical activity, weight, smoking, and family history of disease. The purpose of our study is to identify nutritional risk factors or protective factors for these diseases, which is an essential step in establishing dietary recommendations to prevent the risk of disease and improve the health of the current and future generations. This is the ambitious goal of the NutriNet-Santé study and that is why researchers need you.
During each multimedia recruitment campaign and during the enrollment process, participants are informed that follow-up over at least 10 years is planned.
Previous findings showed that most of the participants enrolled after hearing about the study on television because this medium entails the widest reach [
To be included, participants have to fill in on the website an initial set of questionnaires assessing dietary intake, physical activity, anthropometrics, lifestyle, and socioeconomic conditions along with health status. Participants were informed by email that, after inclusion, they would be asked to complete the same questionnaires each year as part of their follow-up. In addition, they are invited to fill in a complementary questionnaire each month. Aspects related to convenience of participation (ie, ≤20 min each month) and confidentiality were also emphasized. In addition, a system of boosting motivation and retention was implemented. In order to forge a sense of community that helps advance research, participants receive a NutriNet-Santé membership card at inclusion and a certificate on completion of each follow-up year/wave. They also receive monthly email with scientific information regarding health and nutrition, and invitations to press conferences about the study results. For purposes of retention, free screening tests for cholesterol, triglycerides, and diabetes are offered to participants (the results are sent back with a special notice in case of abnormal test results).
All baseline questionnaires were first pilot-tested and compared with traditional administration methods (paper-and-pencil versions or interviews by a dietitian) [
This study was conducted according to guidelines laid down in the Declaration of Helsinki, and all procedures were approved by the Institutional Review Board of the French Institute for Health and Medical Research (IRB Inserm no: 0000388FWA00005831) and the Commission Nationale Informatique et Libertés (CNIL no: 908450 and no: 909216). Written electronic informed consent to participate in the study was obtained from all participants.
Participants were asked, “Would you have participated in the NutriNet-Santé study if it were not Internet-based?” (response options: yes, no, I don’t know). We also asked the participants, “What was your main reason for participating in the NutriNet-Santé study?” The response options for the different motives were classified into 2 general categories: (1) intrinsic motives for participation, including, to help advance public health research on chronic disease prevention, to help advance nutrition research, to receive regular scientific information about health and nutrition, out of curiosity, to belong to a group, or other motives and (2) extrinsic motives, including in response to the call from the media, from a close friend/associate, or from a medical provider. Finally, we asked participants, “Is the fact that the study is exclusively funded by public sources important for your participation?” (response options: very important, important, not very important, not important).
At baseline, sociodemographic, lifestyle, and health characteristics were self-reported. Participants indicated their alcohol consumption frequency and quantity over the previous 7 days. Alcohol intake was calculated by multiplying the alcohol content (ie, percentage) of each beverage (wine, beer, spirits, and cider) by the standard ethanol weight content. Body mass index (BMI) was assessed using self-reported height and weight. Status regarding type 2 diabetes, hypertension, and hypercholesterolemia was provided by participants by answering the following question: “Have you been or are you currently being treated for type 2 diabetes / hypertension / hypercholesterolemia?” If the participant answered yes, he/she completed the information by self-reporting the year of diagnosis and current use of medication.
The present analyses focused on data from a random sample of participants in the NutriNet-Santé cohort who had completed the questionnaire assessing their participation motives and who had no missing sociodemographic, lifestyle, anthropometric, or health status data. These characteristics were compared between participants included in our analysis and those who had stopped participating within 6 months after their enrollment (calculated from the date of the last connection on the website), using a chi-square goodness-of-fit test. The possible reasons for participation were grouped into the following 4 categories: (1) to help advance public health research on chronic disease prevention, (2) to help advance nutrition research, (3) in response to the call from the media, from a close friend/associate or from a medical provider, and (4) other motives (ie, to receive regular scientific information about health and nutrition, out of curiosity, to belong to a group, and other). Perceptions/attitudes toward the public funding of the study were categorized into 3 groups: very important, important, and not important.
According to French recommendations [
A total of 6556 of 15,000 persons completed the motives questionnaire (ie, 43.71% of the randomly invited cohort participants). We excluded 61 individuals with missing data regarding the socioeconomic characteristics, 135 participants with missing data regarding weight or height, and 11 participants with missing data regarding alcohol consumption; therefore, data from 6352 participants was available for analysis. At the time of the administration of the questionnaire about motives, the mean duration of participation in the cohort for the participants included in this analysis was 20 months (SD 4.00) and the median was 23 months (range 1-24). Characteristics of the sample are presented in
Compared with nonrespondents (among the 15,000 contacted participants), the percentages of individuals older than 55 years and of managerial staff were higher among participants included in this analysis, whereas the percentage of individuals with at least 1 child at home was lower (data not shown). Compared with participants who stopped participating within 6 months after their inclusion in the cohort (mean duration of participation: 3 weeks after inclusion, SD 1 week), the percentages of individuals older than 45 years, of married persons, managerial staff, persons with high educational level, individuals who reported hypertension, and those who reported hypercholesterolemia were higher among participants included in this analysis, whereas the percentages of individuals with at least 1 child at home, manual workers/employees, infrequent alcohol consumers, smokers, and obese individuals were lower (
Among participants, 46.45% (2951/6352) reported that they would not have enrolled had the study not been conducted on the Internet, whereas 28.75% (1826/6352) were not sure (
Characteristics of the sample.a
Individual characteristics | Present sample, n (%) |
Drop-out,b n (%) |
|
|
|
|
|
|
Female | 4821 (75.90) | 7584 (75.98) |
|
Male | 1531 (24.10) | 2398 (24.02) |
|
|
|
|
|
18-25 | 480 (7.56) | 1482 (14.85) |
|
26-35 | 1133 (17.84) | 2630 (26.35) |
|
36-45 | 1211 (19.06) | 2276 (22.80) |
|
46-55 | 1344 (21.16) | 1843 (18.46) |
|
>55 | 2184 (34.38) | 1750 (17.54 |
|
|
|
|
|
Married or living with a partner | 4680 (73.68) | 6739 (67.51) |
|
Single, divorced, widowed | 1672 (26.32) | 3243 (32.49) |
|
|
|
|
|
Yes | 1976 (31.11) | 3946 (39.53) |
|
No | 4376 (68.89) | 6036 (60.47) |
|
|
|
|
|
Advanced/graduate degree | 2031 (31.98) | 2414 (24.18) |
|
College graduate | 1868 (29.41) | 2856 (28.61) |
|
Secondary | 2233 (35.15) | 4261 (42.69) |
|
Elementary school | 220 (3.46) | 451 (4.52) |
|
|
|
|
|
Managerial staff | 2215 (34.87) | 2437 (24.41) |
|
Self-employed, farmer | 198 (3.12) | 424 (4.25) |
|
Intermediate profession | 1673 (26.34) | 2101 (21.05) |
|
Employee, manual worker | 1959 (30.84) | 4389 (43.97) |
|
Never-employed/homemaker | 307 (4.83) | 631 (6.32) |
|
|
|
|
|
Rural | 1393 (21.98) | 2014 (20.18) |
|
Semiurban, population <20,000 | 997 (15.71) | 1445 (14.48) |
|
Urban, population between 20,000-100,000 | 784 (12.39) | 1243 (12.45) |
|
Urban, population ≥100,000 | 2118 (33.23) | 3408 (34.14) |
|
Urban, Paris | 1060 (16.69) | 1872 (18.75) |
|
|
|
|
|
Abstainers and infrequent consumers (<once a week) | 1635 (25.74) | 2920 (29.25) |
|
Moderate consumption (≤20 g/day for women and ≤30 g/day for men) | 4192 (65.99) | 6308 (63.19) |
|
Heavy consumption (>20 g/day for women and >30 g/day for men) | 525 (8.27) | 754 (7.55) |
|
|
|
|
|
Never smoker | 3195 (50.30) | 4374 (43.82) |
|
Former smoker | 2200 (34.63) | 2858 (28.63) |
|
Current smoker | 957 (15.07) | 2750 (27.55) |
|
|
|
|
|
Normal (<25 kg/m2) | 4410 (69.43) | 6461 (64.73) |
|
Overweight (≥25 kg/m2-30 kg/m2>) | 1382 (21.76) | 2262 (22.66) |
|
Obese (≥30 kg/m2) | 560 (8.82) | 1259 (12.61) |
Self-reported type 2 diabetes (yes) | 157 (2.47) | 206 (2.06) | |
Self-reported hypertension (yes) | 876 (13.79) | 982 (9.84) | |
Self-reported hypercholesterolemia (yes) | 755 (11.89) | 678 (6.79) |
aAll
bIndividuals who stopped participating within 6 months after their inclusion in the cohort.
Motives for participation in the NutriNet-Santé cohort study (N=6352).
Motives for participation | n (%) | |
|
|
|
|
To help advance nutrition research | 1413 (22.24) |
|
To help advance public health research on chronic disease prevention | 3898 (61.37) |
|
In response to the call for volunteers (from media, a friend/associate or a medical provider) | 438 (6.89) |
|
Othera | 603 (9.50) |
|
|
|
|
Yes | 1575 (24.80) |
|
No | 2951 (46.45) |
|
Don’t know | 1826 (28.75) |
|
|
|
|
Very important | 2185 (34.40) |
|
Important | 2072 (32.62) |
|
Not important | 2095 (32.98) |
aOther category includes participation to receive regular scientific information about health and nutrition, out of curiosity, to belong to a group, and other.
Compared to women, men were more inclined to be motivated by the Internet aspect (
Sociodemographic, lifestyle, and health characteristics associated with motives for participation in the study had it not been Internet-based (multivariate analysis, N=6352)
Individual characteristics | No, I would not have enrolleda | I don’t knowa | |||
|
OR | 95% CI | OR | 95% CI | |
|
|
|
|
|
|
|
Female | 1.00 |
|
1.00 |
|
|
Male | 1.22 | 1.04-1.43 | 0.96 | 0.80-1.14 |
|
|
|
|
|
|
|
18-25 | 1.21 | 0.86-1.70 | 1.19 | 0.82-1.73 |
|
26-35 | 1.51 | 1.20-1.91 | 1.39 | 1.08-1.79 |
|
36-45 | 1.00 |
|
1.00 |
|
|
46-55 | 0.90 | 0.74-1.11 | 0.86 | 0.68-1.07 |
|
>55 | 0.61 | 0.49- 0.76 | 0.76 | 0.59-0.96 |
|
|
|
|
|
|
|
Married or living with a partner | 1.00 |
|
1.00 |
|
|
Single, divorced, widowed | 0.97 | 0.83-1.13 | 1.00 | 0.85-1.18 |
|
|
|
|
|
|
|
Yes | 1.00 |
|
1.00 |
|
|
No | 1.23 | 1.04-1.46 | 1.22 | 1.02-1.47 |
|
|
|
|
|
|
|
Advanced/graduate degree | 1.00 |
|
1.00 |
|
|
College graduate | 1.10 | 0.92-1.31 | 0.98 | 0.81-1.19 |
|
Secondary | 1.10 | 0.91-1.33 | 1.00 | 0.82-1.24 |
|
Elementary school | 1.18 | 0.80-1.74 | 1.38 | 0.92-2.07 |
|
|
|
|
|
|
|
Managerial staff | 1.00 |
|
1.00 |
|
|
Self-employed, farmer | 1.09 | 0.74-1.60 | 1.14 | 0.75-1.75 |
|
Intermediate profession | 0.80 | 0.67-0.96 | 1.04 | 0.85-1.26 |
|
Employee, manual worker | 0.77 | 0.63-0.93 | 0.89 | 0.72-1.10 |
|
Never-employed/homemaker | 1.03 | 0.69-1.55 | 1.21 | 0.78-1.87 |
|
|
|
|
|
|
|
Rural | 1.00 |
|
1.00 |
|
|
Semiurban population <20,000 | 1.01 | 0.83-1.23 | 1.07 | 0.85-1.34 |
|
Urban, population between 20,000-100,000 | 0.81 | 0.65-1.01 | 0.85 | 0.67-1.08 |
|
Urban, population ≥100,000 | 0.91 | 0.77-1.08 | 0.98 | 0.81-1.18 |
|
Urban, Paris | 1.00 | 0.81-1.23 | 1.03 | 0.82-1.29 |
|
|
|
|
|
|
|
Abstainers and infrequent consumers (<once a week) | 1.00 |
|
|
|
|
Moderate consumption (≤ 20 g/day for women and ≤30 g/day for men) | 1.18 | 1.02-1.37 | 1.20 | 1.02-1.40 |
|
Heavy consumption (>20 g/day for women and >30 g/day for men) | 1.19 | 0.92-1.53 | 0.98 | 0.74-1.31 |
|
|
|
|
|
|
|
Never smoker | 1.00 |
|
1.00 |
|
|
Former smoker | 0.97 | 0.84-1.12 | 1.01 | 0.86-1.18 |
|
Current smoker | 0.94 | 0.78-1.13 | 1.01 | 0.82-1.24 |
|
|
|
|
|
|
|
Normal (<25 kg/m2) | 1.00 |
|
1.00 |
|
|
Overweight (≥25 kg/m2-30 kg/m2>) | 1.07 | 0.91-1.25 | 1.09 | 0.92-1.30 |
|
Obese (≥30 kg/m2) | 1.32 | 1.04-1.65 | 1.44 | 1.11-1.86 |
Self-reported type 2 diabetes (yes) | 0.90 | 0.61-1.34 | 0.70 | 0.44-1.10 | |
Self-reported hypertension (yes) | 1,06 | 0.87-1.28 | 0.92 | 0.74-1.14 | |
Self-reported hypercholesterolemia (yes) | 1.05 | 0.86-1.28 | 1.04 | 0.83-1.30 |
aThe question was “Would you have participated in the study if it were not Internet-based?” Reference category for the outcome variable was “Yes, I would still participate even if the study was not Internet-based.”
Regarding reasons for participation, 61.37% (3898/6352) reported participating to help advance public health research on chronic disease prevention; 22.24% (1413/6352) to help advance nutrition-focused research; 6.89% (438/6352) in response to a call from the media, a close friend/relative, or a medical professional; and 9.50% (603/6352) for other reasons (
Exclusive public funding for the study was important for two-thirds of the participants. Among them, half (2185/6352, 34.40%) considered it as very important (
Sociodemographic, lifestyle, and health characteristics associated with reasons for participation in the study (multivariate analysis, N=6352).
Individual characteristics | To help advance public research on chronic disease preventiona | To help advance nutrition researcha | In response to the call (from the media, a friend/associate or a medical provider)a | ||||
|
OR | 95% CI | OR | 95% CI | OR | 95% CI | |
|
|
|
|
|
|
|
|
|
Female | 1.00 |
|
1.00 |
|
1.00 |
|
|
Male | 1.02 | 0.82-1.27 | 0.86 | 0.67-1.09 | 0.96 | 0.70-1.32 |
|
|
|
|
|
|
|
|
|
18-25 | 1.00 |
|
1.00 |
|
1.00 |
|
|
26-35 | 1.08 | 0.72-1.61 | 1.43 | 0.91-2.25 | 1.05 | 0.59-1.89 |
|
36-45 | 1.31 | 0.85-2.01 | 1.55 | 0.96-2.51 | 1.00 | 0.53-1.87 |
|
46-55 | 1.63 | 1.07-2.48 | 1.74 | 1.09-2.79 | 1.48 | 0.81-2.69 |
|
> 55 | 1.62 | 1.07-2.46 | 1.43 | 0.90-2.29 | 1.33 | 0.73-2.41 |
|
|
|
|
|
|
|
|
|
Married or living with a partner | 1.00 |
|
1.00 |
|
1.00 |
|
|
Single, divorced, widowed | 0.82 | 0.67-1.01 | 0.79 | 0.63-0.99 | 0.69 | 0.51-0.94 |
|
|
|
|
|
|
|
|
|
Yes | 1.00 |
|
1.00 |
|
1.00 |
|
|
No | 1.02 | 0.82-1.29 | 0.9 | 0.70-1.15 | 1.08 | 0.78-1.49 |
|
|
|
|
|
|
|
|
|
Advanced/graduate degree | 1.00 |
|
1.00 |
|
1.00 |
|
|
College graduate | 1.01 | 0.79-1.28 | 1.17 | 0.90-1.52 | 1.17 | 0.82-1.66 |
|
Secondary | 1.13 | 0.86-1.47 | 0.97 | 0.72-1.31 | 1.21 | 0.82-1.78 |
|
Elementary school | 1.39 | 0.80-2.40 | 0.66 | 0.34-1.29 | 1.26 | 0.59-2.72 |
|
|
|
|
|
|
|
|
|
Managerial staff | 1.00 |
|
1.00 |
|
1.00 |
|
|
Self-employed, farmer | 1.51 | 0.79-2.89 | 1.51 | 0.75-3.04 | 2.23 | 0.99-5.00 |
|
Intermediate profession | 0.97 | 0.75-1.25 | 0.89 | 0.68-1.18 | 1.02 | 0.71-1.48 |
|
Employee, manual worker | 0.85 | 0.65-1.10 | 0.75 | 0.56-1.00 | 1.14 | 0.78-1.67 |
|
Never-employed/homemaker | 0.56 | 0.35-0.91 | 0.77 | 0.46-1.31 | 0.98 | 0.49-1.96 |
|
|
|
|
|
|
|
|
|
Rural | 1.00 |
|
1.00 |
|
1.00 |
|
|
Semiurban, population <20,000 | 1.28 | 0.95-1.72 | 1.15 | 0.83-1.60 | 1.03 | 0.68-1.56 |
|
Urban, population between 20,000-100,000 | 0.99 | 0.73-1.34 | 1.03 | 0.73-1.44 | 1.01 | 0.66-1.56 |
|
Urban, population ≥100,000 | 0.96 | 0.76-1.21 | 0.95 | 0.73-1.23 | 0.91 | 0.65-1.28 |
|
Urban, Paris | 1.28 | 0.95-1.72 | 1.07 | 0.77-1.48 | 1.12 | 0.74-1.70 |
|
|
|
|
|
|
|
|
|
Abstainers and infrequent consumers (<once a week) | 1.00 |
|
1.00 |
|
1.00 |
|
|
Moderate consumption (≤20 g/day for women and ≤30 g/day for men) | 0.84 | 0.68-1.03 | 0.84 | 0.66-1.06 | 0.80 | 0.60-1.08 |
|
Heavy consumption (>20 g/day for women and >30 g/day for men) | 0.85 | 0.59-1.22 | 0.84 | 0.56-1.26 | 0.80 | 0.48-1.34 |
|
|
|
|
|
|
|
|
|
Never smoker | 1.00 |
|
1.00 |
|
1.00 |
|
|
Former smoker | 0.88 | 0.72-1.08 | 0.83 | 0.66-1.04 | 0.83 | 0.62-1.11 |
|
Current smoker | 0.91 | 0.71-1.18 | 0.96 | 0.72-1.27 | 1.02 | 0.71-1.47 |
|
|
|
|
|
|
|
|
|
Normal (<25 kg/m2) | 1.00 |
|
1.00 |
|
1.00 |
|
|
Overweight (≥25 kg/m2-30 kg/m2>) | 0.72 | 0.58-0.89 | 0.72 | 0.57-0.92 | 0.94 | 0.69-1.28 |
|
Obese (≥30 kg/m2) | 0.62 | 0.46-0.84 | 0.71 | 0.50-1.00 | 0.80 | 0.52-1.24 |
Self-reported type 2 diabetes (yes) | 1.77 | 0.87-3.60 | 1.59 | 0.73-3.49 | 2.05 | 0.84-5.01 | |
Self-reported hypertension (yes) | 0.83 | 0.63-1.09 | 0.81 | 0.59-1.11 | 0.83 | 0.56-1.23 | |
Self-reported hypercholesterolemia (yes) | 1.30 | 0.95-1.77 | 1.23 | 0.87-1.74 | 1.08 | 0.70-1.68 |
aThe question was “What was your main reason to participate in the study?” Reference category for the outcome variable was “other reasons” which includes participation to receive regular scientific information about health and nutrition, out of curiosity, to belong to a group, and other.
Sociodemographic, lifestyle, and health characteristics associated with importance for exclusive public funding (multivariate analysis, N=6352).
Individual characteristics | Very importanta | Importanta | |||
|
OR | 95% CI | OR | 95% CI | |
|
|
|
|
|
|
|
Female | 1.00 |
|
1.00 |
|
|
Male | 1.37 | 1.17-1.61 | 1.21 | 1.03-1.42 |
|
|
|
|
|
|
|
18-25 | 0.40 | 0.28-0.58 | 0.57 | 0.41-0.78 |
|
26-35 | 0.63 | 0.51-0.79 | 0.79 | 0.64-0.97 |
|
36-45 | 1.00 |
|
1.00 |
|
|
46-55 | 1.49 | 1.21-1.83 | 1.14 | 0.93-1.40 |
|
> 55 | 1.97 | 1.57-2.47 | 1.37 | 1.09-1.71 |
|
|
|
|
|
|
|
Married or living with a partner | 1.00 |
|
1.00 |
|
|
Single, divorced, widowed | 0.96 | 0.82-1.12 | 1.09 | 0.94-1.26 |
|
|
|
|
|
|
|
Yes | 1.00 |
|
1.00 |
|
|
No | 0.81 | 0.68-0.95 | 0.94 | 0.80-1.11 |
|
|
|
|
|
|
|
Advanced/graduate degree | 1.00 |
|
1.00 |
|
|
College graduate | 0.80 | 0.67-0.96 | 0.92 | 0.77-1.10 |
|
Secondary | 0.41 | 0.34-0.50 | 0.61 | 0.50-0.74 |
|
Elementary school | 0.38 | 0.26-0.57 | 0.63 | 0.44-0.92 |
|
|
|
|
|
|
|
Managerial staff | 1.00 |
|
1.00 |
|
|
Self-employed, farmer | 0.63 | 0.43-0.93 | 0.87 | 0.61-1.26 |
|
Intermediate profession | 0.87 | 0.73-1.04 | 0.90 | 0.75-1.08 |
|
Employee, manual worker | 0.54 | 0.44-0.65 | 0.71 | 0.59-0.86 |
|
Never-employed/homemaker | 0.76 | 0.50-1.15 | 1.16 | 0.81-1.66 |
|
|
|
|
|
|
|
Rural | 1.00 |
|
1.00 |
|
|
Semiurban, population <20,000 | 1.02 | 0.83-1.26 | 1.06 | 0.86-1.30 |
|
Urban, population between 20,000-100,000 | 0.95 | 0.76-1.18 | 0.93 | 0.75-1.16 |
|
Urban, population ≥100,000 | 1.08 | 0.91-1.29 | 1.04 | 0.88-1.24 |
|
Urban, Paris | 0.97 | 0.78-1.19 | 1.01 | 0.82-1.24 |
|
|
|
|
|
|
|
Abstainers and infrequent consumers <once a week) | 1.00 |
|
1.00 |
|
|
Moderate consumption ≤20 g/day for women and ≤30 g/day for men) | 0.99 | 0.86-1.16 | 0.97 | 0.84-1.13 |
|
Heavy consumption >20 g/day for women and >30 g/day for men) | 0.78 | 0.60-1.02 | 1.00 | 0.78-1.29 |
|
|
|
|
|
|
|
Never smoker | 1.00 |
|
1.00 |
|
|
Former smoker | 1.08 | 0.93-1.25 | 1.12 | 0.97-1.30 |
|
Current smoker | 1.12 | 0.93-1.35 | 1.03 | 0.86-1.24 |
|
|
|
|
|
|
|
Normal <25 kg/m2) | 1.00 |
|
1.00 |
|
|
Overweight ≥25 kg/m2-30 kg/m2>) | 0.89 | 0.76-1.05 | 0.92 | 0.78-1.08 |
|
Obese ≥ 30 kg/m2) | 0.80 | 0.63-1.01 | 0.78 | 0.62-0.98 |
Self-reported type 2 diabetes (yes) | 1.06 | 0.69-1.61 | 0.92 | 0.60-1.42 | |
Self-reported hypertension (yes) | 1.16 | 0.94-1.42 | 1.13 | 0.92-1.39 | |
Self-reported hypercholesterolemia (yes) | 1.13 | 0.91-1.40 | 1.18 | 0.95-1.46 |
aThe question was “Is the fact that the study is exclusively funded by public sources important for your participation?” Reference category for the outcome variable was “not important.”
Profiles of participants in a Web-based epidemiological cohort have rarely been studied [
Our findings revealed that almost half of the participants reported that Internet use was a decisive reason for participation. In fact, this element exerted a stronger influence among men, persons younger than 35 years, individuals of higher socioeconomic status, those without children at home, moderate alcohol consumers, and obese persons. Our results are concordant with previous studies that compared sociodemographic and lifestyle characteristics of participants who used Web-based questionnaires with those of participants who used paper-and-pencil instruments [
In addition, our study indicated that participation in an exclusively Web-based nutrition cohort was driven mainly by a desire to help advance research on chronic disease prevention or nutrition, especially among older participants, those with normal weight, and those who lived with a partner. Our results are also consistent with existing knowledge regarding motives for participation in volunteer-based cohorts on health and nutrition, which do not use the Internet [
Two-thirds of our sample found the use of Internet for completion of the questionnaires to be a benefit, given its flexibility, whereas less than 1% found it to be complex. Also, one-quarter of participants felt more comfortable filling in the questionnaires on the website rather than face to face with an investigator. On the other hand, only 22% visited sections of the website of the study regarding news and progress of the study. Thus, in Web-based studies, the reduced participant burden (eg, quick, easy and convenient access, increased distance between participant and investigator allowing participants not to feel judged) [
Participation in the study for altruistic reasons may be reinforced by the public nature of the research. Indeed, two-thirds of the participants considered the exclusive public funding as important or very important, with the link being particularly pronounced in men, older adults, and individuals of higher socioeconomic status. This finding is not surprising in a European context in which the majority of cohort studies are funded by public organizations. Indeed, 94% of French participants in an opinion survey conducted in the general French population reported that a large part of biomedical research needs to be funded by public funding, and 80% of responders feared that the increased participation of private funding in public research could undermine the independence of research and is damaging to certain research areas deemed less profitable [
Our study has several limitations. First, responders were older and belonged to higher socioeconomic strata than nonrespondents, which might have led to an underestimation of the observed associations. Moreover, our result suggests that the influence of weight status on participation is open to question because participants in a long-term cohort are likely to be particularly health conscious and interested in nutritional issues. In addition, results may reflect the motives of participants accustomed to the study rather than their motives for enrollment in the Web-based cohort because the questions about motives were asked approximately 2 years after baseline. However, key information on exposure and potential confounding factors was collected during the first 2 years of participation in the cohort. Thus, a focus on the motives of those participants who actively participated 2 years after their inclusion is useful in terms of retention strategies during decisive periods of data collection in Web-based cohorts. In addition, the percentage distributions of the given reasons for participation could be biased due the use of a predefined list of response options. However, the participants had the opportunity to choose the “other” response option and to specify the exact reason for participation. Another limitation was the lack of information on reasons for declining participation because the call for participation was not delivered to a predefined list of individuals. Finally, anthropometric status was assessed by self-reporting and may have led to misclassification. However, in a separate validation study that used data from a subsample of 2513 participants, we compared self-reported and measured height and weight (and the resulting BMI) [
Our study highlighted that the reliance on the Internet, the willingness to help advance public health research, and the exclusive public funding of the study were key motives for participation in this exclusively Web-based cohort. In addition, these motives for participation differed by sociodemographic profile and BMI, but not by lifestyle or health status. These findings can help improve retention of diverse population samples, particularly during important data collection periods.
body mass index
We thank the scientists, dietitians, technicians, and assistants who helped carry out the NutriNet-Santé study, and all dedicated and conscientious volunteers. We especially thank Gwenaël Monot, Mohand Aït-Oufella, Paul Flanzy, Yasmina Chelghoum, Véronique Gourlet, Nathalie Arnault, and Laurent Bourhis. We thank Voluntis (a health care software company) and MXS (a software company specializing in dietary assessment tools) for developing the NutriNet-Santé Web-based interface according to our guidelines.
The NutriNet-Santé study is supported by the French Ministry of Health (DGS), the Institut de Veille Sanitaire (InVS), the Institut National de la Santé et de la Recherche Médicale (Inserm), the Institut National de la Recherche Agronomique (Inra), the Conservatoire National des Arts et Métiers (CNAM), the Institut National de Prévention et d’Education pour la Santé (INPES), the Fondation pour la Recherche Médicale (FRM), and the Université Paris 13.
None declared.