Déterminants et conséquences de l’obésité – apport de la cohorte française NutriNet-Santé

Résumé Les études épidémiologiques d’observation à grande échelle fournissent des informations essentielles au développement des politiques de prévention des maladies chroniques comme l’obésité. Depuis 2009, 29 études sur l’obésité ont été publiées à partir des données de la cohorte française NutriNet-Santé. L’objectif de cet article est d’en présenter pour la première fois une synthèse et d’en déduire l’apport de NutriNet-Santé à la compréhension de l’obésité. Parmi ces études, 5 ont investigué les conséquences de l’obésité, 23 ses déterminants, et 1 son rôle médiateur. Parmi les conséquences de l’obésité étudiées, des facteurs comme la migraine ou la dyspepsie fonctionnelle ont été positivement associés à l’obésité. En revanche, parmi les déterminants de l’obésité, de nombreux facteurs liés à l’alimentation ont été positivement associés à l’obésité (ex : proportion d’aliments ultra-transformés au sein des apports) ou inversement associés (ex : alimentation issue de l’agriculture biologique). Aussi, certains facteurs psychologiques ont été positivement associés (ex : impulsivité) ou inversement associés (ex : optimisme) à l’obésité. Dans NutriNet-Santé, de nouvelles études en lien avec l’obésité sont en cours sur des sujets peu traités comme le COVID-19 ou les troubles mentaux. Summary Large-scale observational epidemiological studies provide essential information for the development of prevention policies for chronic diseases such as obesity. Since 2009, the French NutriNet-Santé cohort has been used as the basis for 29 empirical studies on obesity. The aim of this review is to present a summary of the findings of those studies and to deduce the contribution of NutriNet-Santé to the understanding of obesity. Among the 29 studies, 5 analyzed obesity as an exposure variable, 23 – as an outcome, and 1 – as a moderator. When modelled as a determinant (or exposure), obesity was cross-sectionally and positively associated with migraine and functional dyspepsia, respectively. In turn, when modelled as a consequence (or outcome), obesity was positively associated with different dietary factors, such as the proportion of ultra-processed foods in the diet and preference for fatty food. Other factors were inversely associated with obesity, such as following an organic diet. Some psychological factors were positively (e.g. impulsivity) or inversely associated (e.g. optimism) with obesity risk. In NutriNet-Santé, further studies on obesity are underway, dealing with its association with COVID-19 and mental disorders.

Nutritional risk factors for SARS-CoV-2 infection: a prospective study within the NutriNet-Santé cohort.

BACKGROUND: Nutritional factors are essential for the functioning of the immune system and could therefore play a role in COVID-19 but evidence is needed. Our objective was to study the associations between diet and the risk of SARS-CoV-2 infection in a large population-based sample. METHODS: Our analyses were conducted in the French prospective NutriNet-Santé cohort study (2009-2020). Seroprevalence of anti-SARS-CoV-2 antibodies was assessed by ELISA on dried blood spots. Dietary intakes were derived from repeated 24 h dietary records (at least 6) in the two years preceding the start of the COVID-19 pandemic in France (February 2020). Multi-adjusted logistic regression models were computed. RESULTS: A total of 7766 adults (70.3% women, mean age: 60.3 years) were included, among which 311 were positive for anti-SARS-CoV-2 antibodies. Dietary intakes of vitamin C (OR for 1 SD=0.86 (0.75-0.98), P=0.02), vitamin B9 (OR=0.84 (0.72-0.98), P=0.02), vitamin K (OR=0.86 (0.74-0.99), P=0.04), fibers (OR=0.84 (0.72-0.98), P=0.02), and fruit and vegetables (OR=0.85 (0.74-0.97), P=0.02) were associated to a decreased probability of SARS-CoV-2 infection while dietary intakes of calcium (OR=1.16 (1.01-1.35), P=0.04) and dairy products (OR=1.19 (1.06-1.33), P=0.002) associated to increased odds. No association was detected with other food groups or nutrients or with the overall diet quality. CONCLUSIONS: Higher dietary intakes of fruit and vegetables and, consistently, of vitamin C, folate, vitamin K and fibers were associated with a lower susceptibility to SARS-CoV-2 infection. Beyond its established role in the prevention of non-communicable diseases, diet could therefore also contribute to prevent some infectious diseases such as COVID-19.

Spatial determinants of excess all-cause mortality during the first wave of the COVID-19 epidemic in France.

BACKGROUND: The first wave of the COVID-19 pandemic in France was associated with high excess mortality, and anecdotal evidence pointed to differing excess mortality patterns depending on social and environmental determinants. In this study we aimed to investigate the spatial distribution of excess mortality during the first wave of the COVID-19 pandemic in France and relate it at the subnational level to contextual determinants from various dimensions (socioeconomic, population density, overall health status, healthcare access etc.). We also explored whether the determinants identified at the national level varied depending on geographical location. METHODS: We used available national data on deaths in France to calculate excess mortality by department for three age groups: 0-49, 50-74 and > 74 yrs. between March 1st and April 27th, 2020. We selected 15 variables at the department level that represent four dimensions that may be related to overall mortality at the ecological level, two representing population-level vulnerabilities (morbidity, social deprivation) and two representing environmental-level vulnerabilities (primary healthcare supply, urbanization). We modelled excess mortality by age group for our contextual variables at the department level. We conducted both a global (i.e., country-wide) analysis and a multiscale geographically weighted regression (MGWR) model to account for the spatial variations in excess mortality. RESULTS: In both age groups, excess all-cause mortality was significantly higher in departments where urbanization was higher (50-74 yrs.: ß = 15.33, p < 0.001; > 74 yrs.: ß = 18.24, p < 0.001) and the supply of primary healthcare providers lower (50-74 yrs.: ß = - 8.10, p < 0.001; > 74 yrs.: ß = - 8.27, p < 0.001). In the 50-74 yrs. age group, excess mortality was negatively associated with the supply of pharmacists (ß = - 3.70, p < 0.02) and positively associated with work-related mobility (ß = 4.62, p < 0.003); in the > 74 yrs. age group our measures of deprivation (ß = 15.46, p < 0.05) and morbidity (ß = 0.79, p < 0.008) were associated with excess mortality. Associations between excess mortality and contextual variables varied significantly across departments for both age groups. CONCLUSIONS: Public health strategies aiming at mitigating the effects of future epidemics should consider all dimensions involved to develop efficient and locally tailored policies within the context of an evolving, socially and spatially complex situation.

Diet and physical activity during the coronavirus disease 2019 (COVID-19) lockdown (March-May 2020): results from the French NutriNet-Santé cohort study.

BACKGROUND: Since December 2019, coronavirus disease 2019 (COVID-19) has been spreading steadily, resulting in overwhelmed health-care systems and numerous deaths worldwide. To counter these outcomes, many countries, including France, put in place strict lockdown measures, requiring the temporary closure of all but essential places and causing an unprecedented disruption of daily life. OBJECTIVES: Our objective was to explore potential changes in dietary intake, physical activity, body weight, and food supply during the COVID-19 lockdown and how these differed according to individual characteristics. METHODS: The analyses included 37,252 adults from the French web-based NutriNet-Santé cohort who completed lockdown-specific questionnaires in April-May 2020. Nutrition-related changes and their sociodemographic, lifestyle, and health-status correlates were investigated using multivariable logistic regression models. Clusters of participants were defined using an ascending hierarchical classification of change profiles derived from multiple correspondence analyses. RESULTS: During the lockdown, trends of unfavorable changes were observed: decreased physical activity (reported by 53% of the participants), increased sedentary time (reported by 63%), increased snacking, decreased consumption of fresh food (especially fruit and fish), and increased consumption of sweets, cookies, and cakes. Yet, the opposite trends were also observed: increased home cooking (reported by 40%) and increased physical activity (reported by 19%). Additionally, 35% of the participants gained weight (mean weight gain in these individuals, 1.8 kg ± SD 1.3 kg) and 23% lost weight (2 kg ± SD 1.4 kg weight loss). All of these trends displayed associations with various individual characteristics. CONCLUSIONS: These results suggest that nutrition-related changes occurred during the lockdown in both unfavorable and favorable directions. The observed unfavorable changes should be considered in the event of a future lockdown, and should also be monitored to prevent an increase in the nutrition-related burden of disease, should these diet/physical activity changes be maintained in the long run. Understanding the favorable changes may help extend them on a broader scale. This trial was registered at clinicaltrials.gov as NCT03335644.