Sex differences in the association between sleep duration, diet and body mass index: a birth cohort study.

Sex differences in the effects of sleep duration on dietary intake and eating behaviours were examined prospectively in relation to overweight/obesity at ages 6 and 7. Using data from a representative sample (QLSCD 1998-2010) of children born in the province of Québec (Canada), 1106 children were followed to age 6 and 1015 to 7years. Average nocturnal sleep duration was surveyed annually from 2.5-6years, food-frequency and eating behaviour questionnaires were administered at age 6, and body weight and height were measured at 6 and 7years. Associations were examined longitudinally and mediation examined with adjustments for potential confounders. In boys and girls, shorter sleep duration patterns were associated significantly with less favourable dietary intakes at 6years: boys consumed vegetables and fruits less frequently and meats/alternatives more frequently than boys with longer sleep patterns; and girls consumed vegetables, fruits and milk products less frequently and soft-drinks more frequently than girls with longer sleep patterns. However, boys with shorter sleep patterns were also more likely to eat at irregular hours or to eat too much/fast at 6years. These behaviours, and not dietary intake, mediated an inverse association between sleep duration and overweight/obesity in boys. Sleep duration did not associate with any problem eating behaviours or overweight/obesity in girls. Shorter sleep in early childhood appears to associate with problematic eating behaviours in boys and diet quality in both sexes, regardless of an association with overweight/obesity. This is important for public health and should be considered in relation to other diet-related diseases.