Sleep duration and body mass index: moderating effect of self-perceived stress and age. Results of a cross-sectional population-based study.

The objective of this analysis was to assess whether the association between sleep duration and BMI and between sleep duration and waist circumference is moderated by age and self-perceived stress. We analyzed data from 2034 participants enrolled in 2014 in the cross-sectional study Obesity in Romania Study-study of the prevalence of obesity and related risk factors in Romanian general population (ORO study). Interaction between sleep duration, self-perceived stress and age, with BMI as dependent variable, was statistically significant after adjustment for demographic and lifestyle factors (p value for interaction 0.003). In participants without self-perceived stress, a linear negative association between sleep duration and BMI was observed only in those 18-39 years old (p = 0.049), with BMI decreasing in parallel with increased sleep duration. In participants with self-perceived stress, a U-shaped relationship was observed between BMI and sleep duration in those 40-64 years old, with higher BMI in those sleeping ≤ 6 h and ≥ 9 h/night compared to those sleeping > 6 and < 9 h/night (p = 0.002 and 0.005). Those ≥ 65 years old with self-perceived stress sleeping ≥ 9 h/night had a significantly higher BMI compared to those in other sleep duration categories (p = 0.041 vs. those sleeping ≤ 6 h/night and p = 0.013 vs. to those sleeping > 6 and < 9 h/night). No interaction between age, self-perceived stress and sleep duration, with waist circumference as dependent variable was observed. In our sample, the association between sleep duration and BMI was moderated by self-perceived stress and age.