Unusual effect of sleep on diabetes risk identified

Compared with people who slept seven to eight hours a day, those who slept less than six hours a day had a higher risk of developing type 2 diabetes later in life, according to a study published Tuesday in the journal JAMA Network Open.

“Previous studies have shown that (insufficient daily rest) increases the risk of developing type 2 diabetes, while healthy eating habits, such as regularly eating fruits and vegetables, may reduce the risk,” said Dr. Diana Noga, first author of the study and researcher sleep in the Department of Pharmaceutical Biosciences at Uppsala University in Sweden.

“However, it remains unclear whether people who get too little sleep can reduce their risk of developing type 2 diabetes through a healthy diet,” adds Diana Noga. The authors believe they are the first researchers to try to answer this question.

The study results come from a large group of participants – almost 247,900 people – who took part in the UK Biobank study, which tracked the health of more than half a million people aged 40 to 69 in the UK for at least 10 years. Participants first answered questionnaires about their dietary habits and how many hours of sleep they got every 24 hours, including naps.

Healthy eating criteria included eating two or more pieces of fruit per day, two or more servings of fish per week, or 4 or more tablespoons of vegetables per day, CNN noted.

The criteria also included eating no more than two servings of unprocessed or processed red meat per week—in other words, someone who ate both one serving of unprocessed red meat and one serving of processed red meat in one week could still be considered eating a healthy diet. Each healthy dietary behavior was scored one point, resulting in a score ranging from zero (unhealthiest) to five (healthiest).

Sleeping seven to eight hours a day was defined as normal sleep duration, while six hours was classified as short sleep, moderate as five hours, and “extremely short” as three to four hours.

By the end of the follow-up period, which averaged 12.5 years, 7,905 participants had been diagnosed with type 2 diabetes. The authors found that those who slept less than six hours a day were almost twice as likely to develop the disease as those who slept a normal amount. Regarding the risk of developing type 2 diabetes, there was no significant difference between those who had normal sleep and those who slept six hours. And even for those who ate the healthiest, their diet did not offset the impact of insufficient sleep on the risk of developing diabetes.

“This is another study that shows that while genetics plays a role in the development of chronic diseases such as diabetes, lifestyle factors also play a big role,” said Dr. Liana Wen, an emergency physician and professor of health policy and management at Milken Institute School of Public Health, George Washington University.

“However, most of the time people think about lifestyle factors such as diet and exercise,” Wen added. The study confirms “how important sleep is in preventing chronic disease.”

The study’s design means the results support an association between poor sleep and diabetes, rather than a cause-and-effect relationship, said Dr. Naveed Sattar, professor of cardiometabolic medicine at the school of cardiovascular and metabolic health at the University of Glasgow in Scotland.

According to the study, the results are also based on participants’ memories of their eating and sleeping habits. Confirming a cause-and-effect relationship “would require randomized studies of sleep habits to increase sleep time and see whether this reduces the risk of developing diabetes in those at risk, such as those with prediabetes,” Sattar added.

However, “there is now a wealth of evidence that short sleep affects appetite regulation and leads to excessive consumption of calories, perhaps more dense in nature,” adds Dr. Sattar.

According to Liana Wen, sleep is also linked to the function of glucose metabolism, which is involved in type 2 diabetes.

Getting enough rest can be difficult, but adjusting your nighttime routine can help — starting with setting consistent sleep and wake times and keeping your environment dark, cool, and quiet. A relaxing ritual—like reading a book instead of scrolling through social media, or taking a warm bath or shower—can put your brain in the right state for sleep.

You should also avoid caffeine at least six hours before bed or alcohol before bed, CNN advises. While this may help you fall asleep, it may prevent you from getting deeper sleep during the night.