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13 April 2005
Obesity And Insomnia Linked In Brain Cells 
Unusual "wiring" in the parts of the brain that control sleep and waking might explain the prevalence of insomnia and the condition's association with obesity, according to new research appearing in Cell Metabolism. As obesity has reached epidemic proportions, the incidence of insomnia and sleep deprivation has also risen. Studies of this apparent insomnia-obesity association have suggested a causal link between the two, but the underlying mechanism has remained unclear. The brain cells identified in the new study are called hypocretin/orexin cells, and are located in the region of the brain called the hypothalamus. The researchers found that hypocretin neurons - having important roles in both arousal and appetite - lack the ability of most neurons to filter "noise" from signal, said researchers Tamas Horvath and Xiao-Bing Gao of Yale University School of Medicine. The neurons also rapidly reorganize themselves, becoming even more excitable, in response to stresses such as food deprivation. "If these neurons are over-activated by environmental or mental stress in daily situations, they may support sustained arousal, triggering sleeplessness, leading to overeating," said Horvath. "The more stress you have, the lower the threshold becomes for exciting these hypocretin neurons." "This unique wiring and acute stress-induced plasticity of the hypocretin neurons correlates well with its involvement in the control of arousal and alertness, which are vital to survival," said Horvath. "But it may also be an underlying cause of insomnia and associated metabolic disturbances, including obesity. In addition, insomnia is characteristic of perimenopause, which may lead to increased prevalence of obesity in postmenopausal women." Horvath found that the neurological basis of the link between obesity and insomnia makes them both independent and related products of the overactivated hypocretin system. "People with weight and sleep problems could benefit from cutting back on stressful aspects of their lives, rather than trying to specifically medicate either insomnia or obesity," he concluded.
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