Sex-specific associations of anxiety, insomnia, and their comorbidity with incident obesity in a general-population cohort.

Sleep disorders and, to a lesser extent, anxiety disorders, have been studied independently for their association with weight status. However, these mental disorders are highly comorbid. We investigated the prospective associations of anxiety, insomnia, and anxiety-insomnia comorbidity with obesity risk in general-population adults. Enrollees in the ongoing NutriNet-Santé cohort were selected if they had anxiety (Spielberger's State-Trait Anxiety Inventory [STAI-T], 2013-16) and insomnia data (sleep questionnaire, 2014), were without obesity at baseline, and had body mass index (BMI) data during follow-up. Four baseline morbidity groups were modeled: neither insomnia nor anxiety (reference), high anxiety only (STAI-T ≥ 40), insomnia only, comorbid anxiety, and insomnia. The associations between each of these morbidity groups and incident obesity (BMI ≥30 kg/m2) were assessed using adjusted Cox proportional hazards models. Among 23 797 participants, anxiety, insomnia, and comorbid anxiety and insomnia were present in 21%, 6%, and 7% of men, respectively, and in 29%, 8%, and 14% of women, respectively. Mean follow-up was 6.2 ± 2.0 years. An adjusted significant association between anxiety-insomnia comorbidity and incident obesity was found in men (HR = 1.71, 95% CI: 1.06-2.76) but not in women (HR = 1.00, 95% CI: 0.77-1.30) or in the full sample (HR = 1.12, 95% CI: 0.89-1.42). No associations were observed between anxiety alone or insomnia alone and incident obesity. This large prospective study advances public health knowledge about multimorbidity by suggesting a prospective, sex-specific association between anxiety-insomnia comorbidity and increased risk of new-onset obesity. Upon replication, the findings could help inform obesity prevention programs.