Scientists asked 124 healthy older adults, average age 60, about how often they felt drowsy or fell asleep during the day when they would rather be awake, as well as their napping habits. The group then had regular PET scans over the next 15 years to look for beta-amyloid in the brain, high amounts of which are a hallmark for Alzheimer's.
During the follow-up, the researchers found that people who reported frequent excessive daytime sleepiness were about three times more likely to have beta-amyloid buildup than those who weren't sleepy during the day.
Findings from previous studies suggest that when sleep is inadequate or disrupted — say, because of insomnia, sleep apnea, or any other sleep-related problem — our brains have less time to clear out metabolic debris that can lead to beta-amyloid build up. And if you don't sleep well, you are more likely to fight sleepiness and fatigue the next day.