Researchers have pondered about how sleep relates to cognitive decline.

Answers have been elusive because it is hard to know if insufficient sleep is a symptom of the brain changes that underlie dementia — or if it can actually help cause those changes.

Now, a large new study reports some of the most persuasive findings yet to suggest that people who don’t get enough sleep in their 50s and 60s may be more likely to develop dementia when they are older.

One theory is that the more people are awake, the longer their neurons are active and the more amyloid (a protein in the brain that clumps into plaques in Alzheimer’s) is produced, Dr. Musiek said. 

Another theory is that during sleep, fluid flowing in the brain helps clear out excess proteins, so inadequate sleep means more protein buildup.

Some scientists also think getting sufficient time in certain sleep phases may be important for clearing proteins

Having a regular sleep schedule, avoiding caffeine and alcohol before bedtime and removing phones and computers from the bedroom are among the Centers for Disease Control and Prevention’s “sleep hygiene” guidelines. 

Also, sleep experts say:

• sleeping pills and a lot of other things don’t give you as deep of a sleep and we really want the deep sleep because it’s more restorative.
• naps are OK to catch up on missed sleep, but getting a good night’s sleep should make naps unnecessary.