You probably know the standard advice. Get more sleep, be kinder to your body. For most people, extra hours in bed sound like a win.
But in people with type 2 diabetes, more sleep may be flagging a problem rather than fixing one.
A new six-year study followed 678 Japanese adults with type 2 diabetes. Those who slept eight hours or more a night had nearly double the risk of developing or worsening diabetic kidney disease, compared with those sleeping less than six hours.
The study was published in the Journal of the Endocrine Society and led by researchers at Juntendo University Graduate School of Medicine in Tokyo.
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What the researchers measured
The team tracked Japanese outpatients aged 25 to 70 and sorted them by habitual sleep into four groups. These ran from under six hours up to eight hours or more. Over an average of six years, 215 people hit the study's endpoint.
That endpoint was the first appearance of protein in the urine, or a worsening of protein levels already there. Both are signs the kidneys are under strain.
After adjusting for other lifestyle and diabetes factors, the risk rose steadily with each extra hour of sleep. Compared with the under-six-hour group, the risk was 56 percent higher at seven to eight hours. At eight hours or more, it was 92 percent higher.
Sleep duration was the only lifestyle factor significantly tied to the outcome. The pattern was strongest in older adults and in people who already had early signs of kidney damage.
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Why more sleep might signal a problem
The researchers stress that long sleep did not cause the kidney damage. It is more likely a signal of something else going on in the body.
Co-author Tomoya Mita said longer sleep may be "a readily observable marker of underlying health vulnerability," according to the Endocrine Society statement on the research.
Fatigue, poorly controlled blood sugar, sleep apnea and other conditions can all push a person to sleep longer. Any of those could also be dragging the kidneys down.
That is why the authors do not want the finding read as advice to sleep less. If you have type 2 diabetes and you are regularly sleeping eight hours or more without feeling rested, that is worth mentioning to your doctor.
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Why kidneys matter in type 2 diabetes
Kidney damage is one of the most common serious complications of type 2 diabetes. In the United States, more than 4 in 10 adults with type 2 diabetes are estimated to have chronic kidney disease, according to the Centers for Disease Control and Prevention.
Many do not know it, because early kidney damage rarely causes obvious symptoms.
The new study is observational and comes from a single Japanese cohort, so it cannot prove cause and effect. But sleep is one of the few things a doctor can ask about in a short visit that may hint at trouble long before a lab test does.
Standard checks for diabetic kidney disease still begin with a urine test for albumin and a blood test to estimate kidney function. The study's authors argue sleep duration could be added to that picture, as a simple clue to who may need closer attention.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.