Functional gastrointestinal disorders in 35,447 adults and their association with body mass index.

BACKGROUND

Functional gastrointestinal disorders' (FGIDs) associations with body mass index (BMI) have not been thoroughly investigated in the general population.

AIM

To investigate the overlap between functional dyspepsia (FDy), irritable bowel syndrome (IBS), functional constipation (FC) and functional diarrhoea (FDh) and the relationship between BMI and those diagnoses in a large French adult population.

METHODS

Subjects participating in the Nutrinet-Santé cohort study completed a questionnaire based on Rome III criteria. Anthropometrics, socio-demographical and lifestyle data were collected via self-administered questionnaires. Associations between BMI and FGIDs were investigated with multivariate logistic regression.

RESULTS

A total of 35 447 subjects were included in the analysis. Among subjects with FGIDs, 10.4% presented more than one disorder. [FDy coexisted with IBS (23.6%) and FC (15.1%)]. Associations between BMI and FDy differed according to sex. In females, higher odds were observed for underweight and obesity subgroups (OR = 1.26 (95% CI: 0.99-1.59), OR = 1.35 (1.08-1.69), OR = 1.20 (0.81-1.77), OR = 1.47 (0.89-2.42) for underweight, class I, II and III obesity respectively compared with normal BMI), forming a U-shaped relationship confirmed with nonlinear model (P < 0.001). In females, FDh was associated with BMI [OR = 1.05 (1.03-1.07), P < 0.001]. In males, a negative association between BMI and IBS was observed [OR = 0.97 (0.94-0.99), P=0.04]. Other associations were not significant.

CONCLUSIONS

Our study showed an important overlap in FGIDs, supporting the contention of common pathophysiological mechanisms. Relationships between BMI and FGIDs appeared to be sex-dependent. Interaction by sex in the association between BMI and FGIDs should therefore be further explored.