Metabolic causes and consequences of sleep disorders

In recent years, an increasing amount of evidence has emerged showing that metabolic disturbances influence sleep and that sleep deprivation adversely affects metabolism. Sleep restriction may impair glucose tolerance and alter leptin levels. Physiologically, sleep deprivation creates a misperception of inadequate caloric intake and potentiates development of the Metabolic Syndrome. Excessive daytime sleepiness (EDS) can be produced by sleep problems such as sleep apnea and has also been shown to have an increased prevalence in individuals with endocrine disorders. The interrelationships between sleep, sex hormones, thyroid disorders, and growth hormone regulation in patients with sleep disordered breathing (SDB) are outlined in the present review. Increased prevalence of SDB is seen in diabetes; moreover, glucose control improves upon treatment with continuous positive airway pressure. Sleepiness, however, is more prevalent in obesity even in the absence of SDB. Diabetes is also associated with both sleep onset and sleep maintenance insomnia. The circadian rhythmicity of hormones can impact sleep stages. Perturbation of the circadian clock (eg, in shift work or jet lag) can contribute toward the development of metabolic disorders. In the past, treatment of the underlying metabolic disturbance was considered the mainstay of therapy to improve sleep. However, recent thinking is that the reverse may also be true, ie, improving the sleep disturbance will favorably affect endocrine function.