Nutritional status, growth and sleep habits among Senegalese adolescent girls

Objective: To study the relation between sleep habits, nutritional status, growth and maturation in a group of African adolescent girls. The main hypothesis to be tested was that sleep length could be an effective way to spare energy, and thus malnourished girls sleep longer than normal girls. Design: Three repeated yearly surveys (1997 - 1999) on a subsample of girls drawn from a larger study cohort on growth at adolescence. Setting: The Niakhar district in the central part of Senegal. Subject: In total, 40 girls were initially drawn. Missing girls were replaced at each round by girls having the same characteristics and belonging to the same cohort. Intervention: At each round, data on pubertal development ( breast stages and occurrence of menarche), growth and nutritional status were collected. Adolescents wore an accelerometer for three or four consecutive nights and days at each round. Results: At the beginning of the survey, girls were 13.3 +/- 0.5 y old. They were under international reference values in weight and height. Their mean sleep duration was 8.5 +/- 0.9 h. Their puberty status did not influence their sleep habits; however, they slept more in March than in June, which was related to the seasonal change in daylight. There was a significant relation between body mass index and sleep habits: thinner girls slept a longer time and more quietly than the more corpulent girls. Conclusion: The nutritional status of these girls influenced their sleep habits: this may have been either a direct causal relation or a consequence of a protective attitude on the part of the mothers towards the frailer girls.