Getting under 6 hours of sleep a night midlife increases risk of dementia, study finds Updated 2:58 PM; Today 2:34 PM Mature couple in bed. Husband sleeping while his unhappy and depressed wife is covering her eyes with hands. (Dreamstime/TNS)Dreaamstime/TNS Facebook Share You’re not doing yourself a favor by working long hours and depriving yourself of sleep. A new study indicates you may be setting yourself up for failure — brain failure, that is. The new study published Tuesday in the journal Nature Communications found those with a “sleep duration of six hours or less at age 50 and 60,” showed a higher risk for dementia compared to those who slept seven hours a night. The study followed nearly 8,000 people for 25 years.