Several cultural, social, behavioral, psychological, and environmental factors affect the quality and quantity of sleep. The working professionals often experience fatigue, tiredness, and daytime napping due to irregular working hours and shifts. Evidence shows that the current average sleep of an individual, i.e., 6.8 h/night, is 1.5 h less than that a century ago. The cause of sleep loss is multi-factorial. For instance, 45% of adults report sleeping fewer hours to get more work done, 43% said watching television or using the Internet, and 22% reported suffering from insomnia. The unusual, disturbed, and reduced sleep is associated with glucose intolerance.
An individual suffering from sleep disorder, known as obstructive sleep apnea, experiences: 1) deficiency in the amount of oxygen reaching the tissues by total/partial collapse of upper airways while sleeping (Hypoxia) and 2) inflammation. Frequent Hypoxia triggers an increase in sympathetic activity. Increased sympathetic activity and inflammation lead to insulin resistance condition and eventually to type 2 diabetes.
The results of the studies show that compared to a reference sleep duration of 7-8 h, an individual having either short sleep duration (<6 h) or long sleep duration (>8 h) is at high risk of developing type 2 diabetes. One study looked at the impact of gender on the association between sleep and diabetes. The authors concluded that short sleep duration increases the risk of incidence diabetes in men, whereas, in women, long sleep duration dominates.
Researchers analyzing ethnicity’s effect on the association showed that the prevalence of type 2 diabetes is higher in whites who sleep less than 5 h or more than 8 -9 h compared to blacks. Another study showed that the association is more in Hispanics/Non-Hispanic Whites compared to that in African-Americans. Also, researchers examined the association between daytime napping and type 2 diabetes and showed that an individual taking more than 1 h of daytime nap is at 1.5 times more risk of developing diabetes compared to an individual who does not take a nap during the day.
In the context of sleep quality, the incidence of type 2 diabetes is higher in an individual having difficulty initiating sleep (DIS), and the risk increases with increasing difficulty initiating sleep frequency. Furthermore, the association is more in women having difficulty initiating sleep compared to men.
In summary, there is a strong association between sleep quantity/quality and the incidence of type 2 diabetes. The association is stronger in women sleeping for more duration and in men with short sleep duration. Moreover, this association is affected by ethnicity.
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