News & Research

Impact of Sleep Duration on Obesity and the Glycemic Level in Patients With Type 2 Diabetes: The Fukuoka Diabetes Registry. By Toshiaki Ohkuma and colleagues. Diabetes Care, March 2013, pages 611–617

What is the problem and what is known about it so far?

People in the United States are getting less sleep now than they used to and what they do get is often of poor quality. Sleep is not only critical for mental acuity, but evidence suggests that poor sleep can negatively affect other systems in the body, such as metabolism.

Why did the researchers do this particular study?

While there is evidence that sleeping too little or too much may increase the risk of developing type 2 diabetes, little is known about how sleep duration affects the health of people who already have diabetes.

Who was studied?

The study included 4,870 Japanese adults with type 2 diabetes.

How was the study done?

Researchers grouped the participants based on how many hours of sleep they got each night, on average: less than 4.5, 4.5 to 5.4, 5.5 to 6.4, 6.5 to 7.4, 7.5 to 8.4, and more than 8.5. They also determined the participants’ body mass index (BMI), a proxy for body fat percentage, and their A1C (average blood glucose levels over the previous two to three months).

What did the researchers find?

Short or long sleep durations were associated with higher A1C levels, regardless of physical activity, diet, obesity, or depressive symptoms. The average A1C level for people who slept between 6.5 to 7.4 hours per night was the lowest at 7.3 percent, while those who slept less than 4.5 hours and more than 8.5 hours had average A1Cs of 7.6 percent and 7.4 percent, respectively. Short and long sleep durations were also linked to higher BMIs.

What were the limitations of the study?

The researchers evaluated sleep duration by asking participants to fill out a questionnaire, which may have introduced some error into the study. Also, they did not study the quality of sleep, which some studies have suggested can have an impact on health. Finally, this type of study—an association study—cannot prove that sleeping too much or too little caused the rise in A1C and body fat.

What are the implications of the study?

The findings suggest that people who get more or less than between 6.5 and 7.4 hours of sleep per night are at increased risk for high blood glucose levels. Future studies will be needed to determine whether interventions that focus on helping people get the right amount of sleep can help lower blood glucose levels.

FOR MORE INFORMATION

The Role of Sleep in Type 2 Diabetes

Lack of Sleep Lowers Insulin Sensitivity in Fat Cells

Exercise Cuts Sleep Disorder Risk