Longer sleep was associated with a higher kidney-disease risk
Adults with type 2 diabetes who reported sleeping longer were more likely to experience the onset or progression of diabetic nephropathy in a prospective Japanese cohort study. The finding adds another possible signal clinicians may consider when assessing kidney health, but it does not show that sleeping longer causes kidney disease.
The study, published online October 8 in the Journal of the Endocrine Society, followed 678 Japanese outpatients with type 2 diabetes. Researchers led by Fuki Ikeda of Juntendo University Graduate School of Medicine assessed lifestyle habits at the start of the study and again at two and/or five years, then calculated mean values for lifestyle factors.
During an average follow-up of 6.0 years, with a variation of 2.7 years, 215 participants reached a combined endpoint covering the incidence or progression of diabetic nephropathy. The researchers reported that mean sleep duration was the only lifestyle factor associated with that endpoint.
A graded association across reported sleep duration
The analysis compared participants who slept less than six hours a night with groups reporting progressively longer average sleep. After multivariable adjustment, the hazard ratios for the kidney endpoint were 1.08 for people sleeping six to less than seven hours, 1.56 for those sleeping seven to less than eight hours, and 1.92 for those sleeping eight hours or more.
In plain terms, the association was strongest in the group reporting at least eight hours of sleep. The reported relationship remained statistically significant after the researchers adjusted for key lifestyle and diabetes-related factors.
The pattern was also more pronounced among older participants and among people who already had microalbuminuria or reduced kidney function. Microalbuminuria refers to a small but abnormal amount of albumin in the urine and can be an early indicator of kidney damage. Those subgroup findings suggest that sleep duration could be most informative in people who already have reasons to warrant closer kidney monitoring.
An observational result, not a prescription to sleep less
The study’s central limitation is also its most important practical message: it was observational. It tracked an association between reported sleep duration and later kidney outcomes, rather than assigning participants to different sleep schedules. That means the research cannot establish whether longer sleep itself contributes to kidney disease, whether early health changes lead people to sleep longer, or whether another factor influences both.
Tomoya Mita, a co-author at Juntendo University Graduate School of Medicine, said the results may offer a useful clue for identifying people with diabetes who need closer attention to kidney health. But he also cautioned against interpreting the finding as advice to reduce sleep.
That distinction matters. Sleep duration is influenced by many factors, including age, illness, work patterns, medications and sleep quality. A longer reported sleep period does not necessarily reveal how restorative that sleep was, and the study does not establish a target amount of sleep for people with diabetes.
Why diabetic nephropathy matters
Diabetic nephropathy is kidney damage associated with diabetes. Because diabetes can affect the kidneys over time, identifying people at greater risk of deterioration is important for ongoing care. The study’s composite endpoint focused on both new cases and progression, allowing researchers to examine a clinically relevant spectrum rather than a single late-stage outcome.
The result also highlights the limits of treating lifestyle as a simple checklist. In this cohort, the researchers found an association for mean sleep duration while not finding the same relationship for the other lifestyle factors assessed. That does not make sleep duration a proven cause or a standalone screening test. It does suggest that sleep-related information may deserve attention alongside established measures of diabetes and kidney health.
What the study changes—and what it does not
For researchers, the next question is why the association appeared and whether it is replicated in other populations. Further work would need to examine potential biological pathways, sleep quality, underlying illnesses and the possibility that longer sleep is a marker of pre-existing vulnerability rather than a driver of kidney decline.
For patients and clinicians, the study supports careful interpretation rather than abrupt changes in behavior. The evidence does not say that people with type 2 diabetes should curtail sleep. Instead, it suggests that unusually long reported sleep could be one more conversation point when considering kidney risk, especially for older adults and for people with early signs of kidney impairment.
Several authors disclosed ties to biopharmaceutical and medical-technology industries. The study was published as a prospective cohort analysis, a design that can identify meaningful patterns over time but cannot, on its own, prove causation.
This article is based on reporting by Medical Xpress. Read the original article.
Originally published on medicalxpress.com
