If you have diabetes and love a long nap, a new study suggests your liver health may be at risk.
“We found that in people with type 2 diabetes, poor sleep at night — such as going to bed late, waking up late, sleeping less than seven hours, or poor sleep quality — and naps longer than 30 minutes each increase the risk of developing fatty liver disease,” says the senior author, Xuejiang Gu, MD, PhD, the executive director of the endocrinology department at the First Affiliated Hospital of Wenzhou Medical University in Wenzhou, Zhejiang, China.
The highest risk was seen in those who had both poor nighttime sleep and long naps, says Dr. Gu.
Researchers Compared Nappers and Non-Nappers
The study, which has not yet been published in a medical journal, included nearly 2,000 adults with type 2 diabetes, ages 18 to 85, who didn’t have liver disease when the study began.
Researchers used questionnaires to classify participants as having either good or poor nighttime sleep, depending on four factors: bedtime, wake-up time, nighttime sleep duration, and sleep quality. Then they looked at nap length, defining long naps as more than 30 minutes.
That created four sleep-and-nap groups:
- Good nighttime sleep plus short naps
- Good nighttime sleep plus long naps
- Poor nighttime sleep plus short naps
- Poor nighttime sleep plus long naps
The good-nighttime-sleep, short-nap group served as the comparison group or baseline when estimating how much MASLD risk rose in the other groups.
Finally, investigators tried to control for multiple factors that could affect the findings, including age, sex, diabetes duration, BMI, waist circumference, blood pressure, smoking, drinking, cholesterol problems, HbA1C (a measure of blood sugar levels over several months), and insulin resistance.
During the study period, 379 people developed MASLD.
Compared with people who had good nighttime sleep and short naps, MASLD risk was higher in all other sleep groups:
- Good nighttime sleep plus long naps: 88 percent higher risk
- Poor nighttime sleep plus short naps: More than double the risk
- Poor nighttime sleep plus long naps: More than triple the risk
Naps longer than 30 minutes were also linked with higher MASLD risk within each nighttime sleep group:
- Among people with good nighttime sleep, long naps were associated with an 82 percent higher risk.
- Among people with poor nighttime sleep, long naps were associated with a 40 percent higher risk.
The Study Has Some Limitations
Although the researchers made valid efforts to analyze thoroughly and account for lots of factors, the findings can only show an association between napping and increased risk of MASLD and not that napping caused the increased risk for MASLD, says Joseph Lim, MD, a Yale Medicine hepatologist and professor at Yale School of Medicine in New Haven, Connecticut, who wasn’t involved in the research
According to Dr. Lim, the key issue that the authors could not resolve is the chicken-egg question. Early metabolic changes or another health issue could make people more likely to take longer naps before MASLD is diagnosed, Gu agrees.
More research is needed to better understand the connection. “I don’t think we can conclude that napping is what caused the increased risk in liver disease,” says Marc-Andre Cornier, MD, a professor of medicine and the director of the division of endocrinology, diabetes, and metabolic diseases at the Medical University of South Carolina in Charleston.
“It’s likely that the associated increased risk is due to many factors that can overlap in ways that make cause and effect hard to untangle,” he says.
“Disturbed sleep, whether it’s not enough sleep or poor-quality sleep, can impact circadian rhythms, which then can impact metabolic health, increase appetite, increase food intake, and lead to weight gain,” says Dr. Cornier.
What Is MASLD?
MASLD is the newer name for what many people still know as nonalcoholic fatty liver disease.
In other words, excess fat is stored in the liver, most commonly in people with metabolic problems such as diabetes, obesity, high blood pressure, or high cholesterol, says Cornier.
About 1 in 3 adults have MASLD, but because it often doesn’t cause symptoms, only a fraction of people know that they have it.
For many people, MASLD does not lead to serious complications. But in about 1 in 6 people with MASLD, the liver fat is linked with significant liver injury called MASH, or metabolic dysfunction–associated steatohepatitis, which can lead to liver scarring, cirrhosis (advanced liver scarring), liver failure, or liver cancer, says Lim.
Should You Change Your Sleep Habits to Protect Your Liver?
People with type 2 diabetes should not read this study as a reason to cut out daytime napping or force every nap to be under 30 minutes, says Cornier.
“But the need to take long or frequent naps — especially when they happen alongside poor nighttime sleep or daytime exhaustion — is worth discussing with your doctor because it may be a sign that you’re more likely to develop liver disease or another health issue,” he says.
To reduce the risk of MASLD and protect your overall health:
- Protect nighttime sleep first. Lim recommends keeping a consistent sleep schedule during the week and on weekends, exercising regularly, limiting screen time at night, avoiding alcohol and caffeine in the evening, and aiming for about seven hours of sleep per night.
- Keep naps short when possible. Gu recommends seven to eight hours of good-quality nighttime sleep and naps of 30 minutes or less when needed.
- Focus on evidence-backed lifestyle habits. These include weight loss when appropriate, regular exercise, a balanced diet that focuses on whole foods and lean sources of protein, and diabetes medications that may benefit the liver for some people, says Cornier.
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