Sign up for CNN’s Sleep, But Better newsletter series. Our seven-part guide has helpful hints to achieve better sleep.
Getting only a few hours of sleep per day may do more harm than just causing a groggy day at the office — it may put you at higher risk for developing type 2 diabetes, a new study has found.
Compared with people who got seven to eight hours of sleep per day, those who slept less than six hours daily had a higher risk of developing type 2 diabetes later in life, according to the study published Tuesday in the journal JAMA Network Open.
“Previous research has shown that (insufficient rest on a daily basis) increases the risk of type 2 diabetes, while healthy dietary habits such as regularly eating fruit and vegetables can reduce the risk,” Dr. Diana Nôga, first author of the study and a sleep researcher in the department of pharmaceutical biosciences at Uppsala University in Sweden, said in a news release.
“However, it has remained unclear whether people who sleep too little can reduce their risk of developing type 2 diabetes by eating healthily,” Nôga added. The authors believe they are the first researchers to attempt to answer that question.
The study’s findings draw from a large group of participants — nearly 247,900 people who had participated in the UK Biobank study, which has followed the health outcomes of more than half a million people between ages 40 and 69 in the United Kingdom for at least 10 years. At the beginning, participants answered questionnaires about their dietary habits and about how many hours they slept every 24 hours, including naps.
The criteria for a healthy diet included having eaten two or more pieces of fruit daily, two or more servings of fish weekly, or 4 or more tablespoons of vegetables per day.
The criteria also included eating no more than two servings each of unprocessed or processed red meat weekly — in other words, someone who ate both one serving of unprocessed red meat and one serving of processed red meat within one week could still be considered to have a healthy diet. Each healthy dietary behavior was worth one point, resulting in a score ranging from zero (unhealthiest) to five (healthiest).
Sleeping seven to eight hours daily was defined as normal sleep duration, while six hours was classified as short, moderate as five hours and “extreme short” as three to four hours.
By the end of the follow-up period, which was 12.5 years on average, 7,905 participants had been diagnosed with type 2 diabetes. Those who’d slept less than six hours daily were nearly twice as likely to develop the disease than those who had slept a normal amount, the authors found. In terms of risk for type 2 diabetes, there wasn’t a significant difference between those with normal sleep and those who slept six hours. And even for those who ate the healthiest, their diet didn’t offset the effects of insufficient sleep on diabetes risk.
“This is another study that shows while genetics play a role in the development of chronic diseases such as diabetes, lifestyle factors matter a lot, too,” Dr. Leana Wen, CNN wellness contributor, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health, said via email. Wen wasn’t involved in the study.
“Much of the time, though, people think of lifestyle factors like dietary intake and exercise habits,” Wen added. The study adds support for “just how important sleep is to preventing chronic diseases.”
Sleep and diabetes risk
The study’s design means the findings confirm a link between poor sleep and diabetes, not a cause-and-effect relationship, said Dr. Naveed Sattar, a professor of cardiometabolic medicine in the school of cardiovascular and metabolic health at the University of Glasgow in Scotland, via email.
The findings are also based on participants’ recollections of their food and sleep habits, according to the study. Confirming a causal relationship “would require randomized trials intervening on sleeping habits to increase sleep time and see if this reduces risk of diabetes in those at risk, e.g. those with pre-diabetes,” Sattar added.
However, “there is now plentiful evidence that short sleep influences appetite regulation and leads to overconsumption of calories, perhaps more dense in nature,” Sattar added.
Sleep has also been linked to the function of glucose metabolism, Wen said, which is involved in the cause of type 2 diabetes.
Getting enough rest can be difficult, but adjusting your nightly routine can help — starting with establishing consistent sleep and wake times, and a dark, cool and quiet environment. A wind-down ritual — such as reading a book instead of scrolling through social media or taking a warm bath or shower — can get your brain in the right headspace for sleep.
Also avoid caffeine at least six hours before bedtime or drinking alcohol before bed. Although it may help you fall asleep, it can interfere with getting into deeper stages of sleep throughout the night.
