Many people believe that getting more sleep is always better for health. While enough sleep is important, a new study suggests that regularly sleeping for very long periods may not always be a good sign for the brain.
Researchers found that older adults who usually slept more than about eight and a half hours a night tended to have higher levels of a blood protein linked to Alzheimer’s disease. The findings were published in Alzheimer’s & Dementia, the Journal of the Alzheimer’s Association.
Scientists from UT Health San Antonio analyzed data from 2,410 participants in the long-running Framingham Heart Study. The volunteers had an average age of about 70 years, and just over half were women. Researchers compared participants’ usual sleep duration with several blood markers associated with brain health and neurodegenerative disease.
One protein attracted particular attention. It is called phosphorylated tau 181, or p-tau181, which is a modified form of the tau protein. Abnormal tau proteins build up inside brain cells in people with Alzheimer’s disease, and new blood tests now allow researchers to measure this process without needing more invasive procedures.
The results showed that people who regularly slept between about eight and a half and nine hours had higher p-tau181 levels than those with shorter sleep. The increase became even steeper among people sleeping ten hours or more each night.
This pattern remained even after researchers accounted for factors such as age, sex, depression, sleep apnea, kidney function, and a genetic risk factor for Alzheimer’s disease.
The researchers emphasized that this study does not prove that sleeping longer causes Alzheimer’s disease. Because the research looked at people at only one point in time, it cannot determine which came first. Instead, long sleep may be an early sign that changes are already occurring in the brain before memory problems become obvious.
Previous research has linked both very short and very long sleep with a greater risk of dementia, but the relationship has been difficult to understand. Instead of assuming the relationship followed a straight line, the researchers used advanced statistical methods that allowed them to detect curved patterns.
This approach revealed that the risk marker rose mainly after sleep exceeded about eight and a half hours.
The team also examined three other blood markers linked to brain damage. Once kidney function was considered, those associations disappeared. Only p-tau181 remained strongly linked with long sleep, suggesting the finding may be more specific to Alzheimer’s-related changes than to general aging.
Alzheimer’s disease affects millions of people worldwide and is the leading cause of dementia. Although new treatments can slow the disease for some patients, there is still no cure. Identifying simple warning signs that appear years before symptoms develop could help doctors identify people who may benefit from closer monitoring or future treatments.
The researchers say people should not panic if they occasionally sleep longer than usual. Illness, stress, medications, and poor-quality sleep can all increase the amount of time people spend in bed. However, consistently needing nine to ten hours of sleep without a clear reason may be worth discussing with a healthcare professional.
In review, this study suggests that unusually long sleep may serve as a useful early clue to changes linked with Alzheimer’s disease rather than being a direct cause. The findings need to be confirmed in long-term studies that follow people over many years.
Until then, maintaining healthy sleep habits and speaking with a doctor about persistent changes in sleep remain sensible steps for protecting brain health.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
Source: UT Health San Antonio.
