In the past two decades, sleep has been noted as a relevant factor in the risk of weight gain, but new findings over the last ten years suggest it is not simply hormones in the gut that are affected. In fact, sleep exerts important modulatory effects on several neuroendocrine functions, including glucose regulation. However, human behaviors have changed significantly, reflecting an ever more industrialized nation. Consequently, people are sleeping less and less. Interestingly, this trend toward shorter sleep times has occurred over the same time period as the dramatic increases in the prevalence of obesity and diabetes.
Recent literature publications have demonstrated the accumulating body of evidence that indicates chronic sleep loss may play a real role in the current epidemics of obesity and diabetes; however, this is not specific to the unhealthy. Investigations of healthy young volunteers have shown across the board that experimental sleep restriction is associated with a dysregulation of the neuroendocrine control of appetite consistent with increased hunger as well as with alterations in parameters of glucose tolerance. Both suggest an increased risk of inflammation and diabetes. Epidemiologic findings in both children and adults are consistent with the risks associated with the laboratory data.
One study published in Sleep 2012 supports this notion. Investigators analyzed 245 healthy, high school students for risk of metabolic dysfunction related to sleep loss. The students were asked to keep a daily sleep log and wear a wrist actigraph for one week during the school year. Researchers tracked their sleep duration and insulin resistance levels by analyzing fasting blood glucose levels during the study period and comparing them with the sleep patterns. Sleep duration, based on actigraphy, averaged 6.4 hours during the week. School night sleep was found to be significantly lower than that of the weekends.
Results demonstrated that higher insulin resistance is associated with shorter sleep duration, independent of race, age, gender, waist circumference, and body mass index. According to the lead researcher, the study is the only one in healthy adolescents that shows a relationship between shorter sleep and insulin resistance, independent of obesity. “High levels of insulin resistance can lead to the development of diabetes…We found that if teens that normally get six hours of sleep per night get one extra hour of sleep, they would improve insulin resistance by 9 percent."
Of further relevance, Swedish investigators identified a consistent link between both reduced sleep and psychological well-being and risk for diabetes based on the data collected from the Norwegian HUNT study (n=53,394). Authors stated, “Sleep disturbances and low psychological well-being were associated with an increased risk of autoimmune diabetes primarily linked to poor sleep in men and low well-being in women.” They found that similar associations were seen with type 2 diabetes in relation to sleep problems in men and low well-being in both men and women. The finding suggests well-being is an additional factor; when combined with sleep loss, it may better explain autoimmune diabetes in adults.
According to researchers “Our findings indicate that psychosocial factors influence the risk of autoimmune diabetes in adults, possibly through mechanisms related to insulin resistance. This supports the notion that the etiology of autoimmune diabetes with adult onset in some respects is similar to that of type 2 diabetes.”
Researchers from the Woolcock Institute of Medical Research in Sydney, Australia investigated how sex differences, aging, and obesity may potentially influence the relationship between sleep, metabolic control and subsequent disease. Their findings were consistent with the others in that sleep restriction impeded daytime glucose control and increased appetite. Of further interest is the role sex hormones play in sleep duration and quality and may account for sex differences in the prevalence of sleep-related disorders. Likewise, aging is associated with decreased sleep duration, decreased muscle mass, and impaired insulin action, whereas obesity impairs insulin action and is associated with the incidence and severity of obstructive sleep apnea. These findings clearly suggest that a combination of poor health, age, and lack of sleep increase the potential problems for the onset of metabolic disease. Researchers concluded that sleep plays an integral role in metabolic control; therefore, when sleep patterns are insufficient, sleep may increase one’s risk for developing of Type 2 diabetes.
While a definite number in terms of hours has not been identified for all populations, there are some consistencies that warrant attention:
While more research is needed to clearly identify the interaction between sleep and health, clearly there exists a relevant relationship. A simple goal should be to attain at least seven hours of sleep per night, an amount that has been associated with improved glucose management. And while 8-9 hours may be a stretch for some people, it seems to provide added benefit for recovery from stress and reduced risk for disease.