Four new studies suggested this idea and presented the findings at the Alzheimer's Association meeting. Too little, or too much, sleep was equated with two years of brain aging in one study.
Another study found that people with sleep apnea were more than twice as likely to develop mild thinking problems or dementia.
Researchers working on another study reported that excessive daytime sleepiness may predict diminished memory and thinking skills in older people.
Experts say the studies pave the way for sleep interventions that could stave off mental deterioration.