This study analyzed existing data from a long-term study of nearly 8,000 Britons since 1985, conducted by University College London. As part of a research project, participants report how long they slept many times in 25 years. Some of them also wear sleep tracking to make sure they give an accurate figure on how long they sleep.
Then, a team of researchers looked for any correlation between poor sleep and a higher risk of dementia.
Researchers have long suspected that there is a link between sleep and the risk of dementia, but they’re not sure where that link started. That is, we don’t know whether a lack of sleep can make people suffer from dementia or dementia that deprives everyone.
The key part of this study is that it started tracking sleep patterns of people in their 50s, presumably before dementia appeared.