Older adults who regularly sleep very long hours are showing a possible warning signal in their blood, according to UT Health San Antonio researchers. In a new analysis, people reporting roughly 8.5 to 9 hours of sleep per night and especially those topping 10 hours had higher levels of a phosphorylated form of tau, a protein tied to Alzheimer’s disease. Scientists stress this is an observational link, not evidence that extra shut-eye causes Alzheimer’s.
Study details
The team drew on 2,410 participants from the long-running Framingham Heart Study, with an average age of about 70 and more than 55% women, and measured plasma p-tau181, a phosphorylated tau species now detectable in blood. Using restricted cubic splines to capture non-linear patterns between self-reported sleep duration and several blood biomarkers, researchers found that the association with p-tau181 held up even after adjusting for age, APOE genotype, kidney function and other factors. The findings appear in the journal Alzheimer's & Dementia.
Researchers' caution
Lead author Vanessa M. Young has been careful not to let anyone run too far ahead of the data. She emphasized that “the study does not prove long sleep causes Alzheimer’s” and suggested that routinely sleeping nine to ten hours or more might be better treated as a signal to check in with a clinician than a reason to abruptly overhaul sleep habits. Her comments and that broader context were reported by the San Antonio Express-News.
How scientists interpret the signal
UT Health San Antonio investigators described long sleep as a “potential behavior marker” of elevated p-tau181, pointing to the fact that the pattern appeared specific to p-tau181 compared with other neurodegeneration markers once covariates were taken into account. According to the university’s press information on EurekAlert!, the team noted that the signal might reflect early, Alzheimer-related neurobiology, while underscoring that only longitudinal studies can clarify timing and cause. For now, they see the sleep finding as a possible clinical flag rather than a proven driver of disease.
Where this fits with prior research
This work lines up with previous large studies that have tied both unusually short and unusually long sleep to Alzheimer-related brain changes and later cognitive decline, hinting at a complicated, two-way relationship between sleep and brain health. Research using actigraphy and PET imaging has linked disturbed 24-hour activity rhythms and sleep duration with amyloid and tau shifts, reinforcing the idea that sleep can act as both a risk factor and an early symptom. Experts continue to call for prospective, multi-modal studies that can sort out whether sleep patterns come before biomarker changes or arise as part of early neurodegeneration, as discussed in JAMA Neurology.
Practical takeaways
Clinicians say this study is not a mandate to suddenly cut back on sleep. Instead, if someone is persistently very sleepy or routinely sleeping 9 or more hours a night, that pattern is worth bringing up with a doctor so potential causes such as sleep apnea, depression or medication effects can be checked out. The National Sleep Foundation recommends about 7 to 8 hours of sleep for older adults, which offers a workable benchmark while questions about very long sleep remain unsettled. Blood p-tau tests are an emerging clinical tool, but the Alzheimer's Association advises that they be used alongside specialist evaluation instead of as routine screening for otherwise healthy people.
Researchers at UT Health San Antonio and their collaborators plan further prospective analyses to see whether sleep changes show up before biomarker shifts or trail in their wake. For now, the takeaway is less panic and more vigilance: habitual, unexplained long sleep is something to flag for a clinician, not a reason for alarm all by itself.
