Diabetes
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Some of the association between development of type 2 diabetes and sleep deprivation is probably due to the increased risk of obesity. In addition, poor sleep may alter the hormones involved in glucose metabolism. Sleep also seems to decrease the activity of the parasympathetic nervous system, which plays a role in insulin control and release. One study found that people who were restricted to four-and-a-half hours of sleep for four nights showed a 16-percent drop in their body's overall ability to properly respond to insulin compared to people who slept an average of 7.87 hours.