Getting a good night’s sleep can help keep your immune system strong, maintain your weight, improve your mood, and increase focus throughout the day. It may also help prevent Alzheimer’s, provided you don’t doze too long.
Researchers at Stanford University recently studied the impact a person’s sleep volume had on their brain amyloid-β accumulation and cognitive function, finding that there was a sweet spot that led to the best results. The study can be read in full in JAMA Neurology.
Joe Winer, lead author and postdoctoral research fellow at Stanford, says, “The main takeaway is that it is important to maintain healthy sleep late in life. Additionally, both people who get too little sleep and people who get too much sleep had higher (body-mass index and) more depressive symptoms.”
To conduct the study, researchers looked at data from 4,417 participants in the multi-country Anti-Amyloid Treatment in Asymptomatic Alzheimer’s Disease study. They ranged in age from 65 to 85 and were considered cognitively unimpaired. Participants self-reported their nightly sleep duration, with results grouped into three categories: six or fewer hours, seven to eight hours, and nine or more hours. The responses were compared to the participants’ amyloid- β accumulation, cognitive function, demographics, and lifestyle variables.
Amyloid- β burden was found to increase in those who reported insufficient sleep, but this was not observed in those who had normal and excess sleep levels.
Winer says that elevated numbers are linked with Alzheimer’s, explaining, “Amyloid-β is one of the first detectable markers in the progression of Alzheimer’s disease. In Alzheimer’s disease, amyloid-β proteins start to build up throughout the brain, sticking together in plaques. Amyloid plaques are more likely to appear as we age, and many people with amyloid built up in their brains remain healthy. About 30% of healthy 70-year-olds will have substantial amounts (of) amyloid plaques in their brain.”
While only those who slept too little were found to have elevated amyloid- β burden, those with excess sleep duration suffered other issues. Both groups displayed reduced cognitive abilities, a higher body mass index, depressive symptoms, and more incidence of daytime napping.
There were some differences along racial, educational, and gender lines, as well. Educated women were more apt to sleep longer. In addition, white participants reported an average sleep duration of seven hours and nine minutes, while Black, Asian, and Hispanic white participants reported lower totals. The researchers say this could be linked to other disparities like cardiovascular and metabolic health, socioeconomic factors, and racial discrimination. Other sleep studies have found such correlations.
Though more research needs to be done on the link between sleep and cognitive health, Winer says older adults should consider sleep as important to their health as diet and exercise. The best total is between seven and nine hours per night.