A study published June 18, 2019 in Alzheimer’s & Dementia suggests that napping may also precede the risk of dementia and cognitive decline, reports UCSF.

The study found that men who had napped for an average of two hours or more per day at the beginning of the study were 66 percent more likely to develop clinically significant cognitive impairment than men who had only napped for 30 minutes or less a day. Excessive napping was most strongly linked to later cognitive impairment in men who slept well at night, suggesting that night-time sleep disruption was unlikely to directly explain the relationship, though more subtle interactions could not be ruled out.

Prior studies have suggested a connection between napping and age-related cognitive decline and dementia, but most have relied on retrospective self-reports, which are not very reliable, and none have tracked the consequences of objectively measured 24-hour sleep patterns over such a long period.