Cross-sectional versus Prospective Associations of Sleep Duration with Changes in Relative Weight and Body Fat Distribution: The Whitehall II Study

Saverio Stranges; Francesco P. Cappuccio; Ngianga-Bakwin Kandala; Michelle A. Miller; Frances M. Taggart; Meena Kumari; Jane E. Ferrie; Martin J. Shipley; Eric J. Brunner; Michael G. Marmot

Disclosures

Am J Epidemiol. 2008;167(3):321-329. 

In This Article

Abstract and Introduction

A cross-sectional relation between short sleep and obesity has not been confirmed prospectively. The authors examined the relation between sleep duration and changes in body mass index and waist circumference using the Whitehall II Study, a prospective cohort of 10,308 white-collar British civil servants aged 35-55 years in 1985-1988. Data were gathered in 1997-1999 and 2003-2004. Sleep duration and other covariates were assessed. Changes in body mass index and waist circumference were assessed between the two phases. The incidence of obesity (body mass index: ≥30 kg/m2) was assessed among nonobese participants at baseline. In cross-sectional analyses (n = 5,021), there were significant, inverse associations (p < 0.001) between duration of sleep and both body mass index and waist circumference. Compared with 7 hours of sleep, a short duration of sleep (≤5 hours) was associated with higher body mass index (β =0.82 units, 95% confidence interval (CI): 0.38, 1.26) and waist circumference (β = 1.88 cm, 95% CI: 0.64, 3.12), as well as an increased risk of obesity (odds ratioadjusted = 1.65,95% CI: 1.22, 2.24). In prospective analyses, a short duration of sleep was not associated with significant changes in body mass index (β = –0.06, 95% CI: –0.26, 0.14) or waist circumference (β = 0.44, 95% CI: –0.23,1.12), nor with the incidence of obesity (odds ratioadjusted= 1.05, 95% CI: 0.60, 1.82). There is no temporal relation between short duration of sleep and future changes in measures of body weight and central adiposity.

Numerous epidemiologic studies indicate possible associations between sleep disturbances or voluntary shortened sleep duration and several health outcomes, including total mortality, cardiovascular disease, type 2 diabetes mellitus, respiratory disorders, and poor self-rated health.[1,2,3,4,5,6,7,8,9,10,11,12,13] In addition, several studies have suggested a relation between short sleep duration and increased body weight or obesity in both children and adults.[14,15,16,17,18,19,20,21,22,23,24,25,26] Specifically, an inverse association has been reported between the number of hours of sleep and body weight or body mass index. However, these observations come predominantly from cross-sectional studies.[14,15,16,17,18,19,20,21,22] Results from a few longitudinal analyses have been inconsistent, with only one study showing significant,consistent associations.[23,24,25,26] Specifically, a recently published report from the Nurses' Health Study has shown that a habitual sleep time of less than 7 hours predicted a modest increase in weight and incident obesity independent of baseline weight.[26] This analysis, however, was based on self-reported measures of body weight, was limited to a large cohort of highly selected middle-aged women, and did not take measures of body fat distribution into account. Altogether, the current epidemiologic evidence does not allow for conclusive inferences in favor of a causal link between short sleep duration and obesity because of a number of unresolved issues.[27,28] First, sleep disorders are often comorbid, especially in the elderly, with medical and psychiatric conditions that can compromise the quality and duration of sleep,[29] thus increasing the likelihood of reverse causality and bidirectional relations, especially in cross-sectional studies. Second, the biologic mechanisms underlying the observed associations are unclear, although the evidence from experimental studies suggests possible explanations, such as alterations in hormonal and neurovegetative responses, and effects on the immune function. Third, given the lack of specificity of the observed associations, it is possible that other factors or comorbid conditions may confound the associations between duration and quality of sleep and health outcomes.

The Whitehall II Study gives a unique opportunity to address several of the open questions discussed above. Specifically,in this study, we sought to examine the cross-sectional and longitudinal relations between sleep duration and changes in continuous measures of relative weight (i.e., body mass index (BMI)) and body fat distribution (i.e., waist circumference),as well as the incidence of obesity and overweight, taking into account a number of potential confounding factors.

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