Diabetes and obesity are two debilitating chronic diseases that are increasing at an alarming rate worldwide [1
]. Voluntary sleep restriction may play a role in the rapid increase in the prevalence of diabetes and obesity, and this chapter will review the evidence for such a link. Sleep restriction or impaired sleep may be more common in modern society than in past decades [3
]. A survey study from 1960 found modal sleep duration to be 8.0 to 8.9 hours [5
], while another survey study in 1995 observed a modal category of only 7 hours [6
]. Recent national data also indicate that a greater percentage of adult Americans report sleeping 6 hours or less in 2004 than in 1985 [7
]. Thus, the increase in the prevalence of obesity and diabetes appears to be mirrored by a decrease in average sleep duration in the U.S.
In simplistic terms, weight gain occurs when there is positive energy balance, that is, energy intake is greater than energy expenditure (see ). Sleep restriction could affect endogenous processes related to energy balance, such as impairments in glucose metabolism and an upregulation of appetite. Sleep restriction could also affect exogenous factors such as food choice and increased time available to eat. Sleep loss could also lead to reductions in physical activity or energy expenditure, but evidence in support of this hypothesis is lacking. Both impaired glucose metabolism and excess weight can increase the risk of developing type 2 diabetes. Thus, this chapter will first review laboratory studies that examine the effects of sleep loss on glucose metabolism and appetite regulation. The chapter will then review the epidemiological evidence for an association between sleep restriction and diabetes risk, increased body mass index and risk of obesity.
Schematic representation of potential pathways through which sleep loss may lead to a positive energy balance in which energy intake is greater than energy expenditure.
Sleep disordered breathing is a common sleep disorder that can lead to sleep loss, however it is also associated with sleep fragmentation and hypoxia. Therefore, it is a much more complex condition than behavioral sleep restriction. Chapters 11–13 of this volume discuss the effects of sleep apnea and sleep disordered breathing on health.