Folate and vitamin B-12 status and sleep duration in middle childhood

Insufficient sleep duration is prevalent in middle childhood and is associated with substantial health risks. Few investigations have addressed the role of folate and vitamin B-12 on sleep duration, and no studies have evaluated their potential interaction on sleep. We assessed associations of erythrocyte folate and plasma vitamin B-12 on sleep duration in middle childhood longitudinally, among 1642 participants in the Bogotá School Children Cohort. Nighttime sleep duration was assessed through parental report after a median 2 years of follow-up. We estimated adjusted mean differences in sleep hours with 95 % confidence intervals (CI) by micronutrient concentrations using linear regression with restricted cubic splines. Erythrocyte folate concentration was positively associated with nighttime sleep duration in a non-linear manner. Compared with the median (827 nmol/L), children at the 95th percentile of the distribution (1274 nmol/L) had an adjusted 0.26 (95 % CI: 0.07, 0.44) hours longer sleep duration. There was a significant interaction between folate and vitamin B-12; the association between folate and sleep duration was only apparent in children with low vitamin B-12 status (<221 pmol/L). In this group, the adjusted mean difference (95 % CI) in sleep duration between the 95th and the 50th percentiles of folate was 0.61 (0.17, 1.04) hours, whereas in children with vitamin B-12 ≥ 221 pmol/L the difference was 0.11 (-0.10, 0.32) (P, interaction = 0.01). Vitamin B-12 was not associated with sleep duration. Erythrocyte folate is positively associated with nighttime sleep duration in children with low vitamin B-12 serostatus.