A nap a day keeps mental degradation at bay, a new paper suggests. The findings showcase that individuals who took regular afternoon naps showed better mental capacity over time.
As we age, the tissues making up our bodies physically wear down. Given the longer life expectancies of today (compared to our natural baseline), this creates many more opportunities for neurodegenerative conditions, such as dementia. While napping won't keep us perfectly safe from such issues, it does seem to promote mental agility and stave off mental decline over time.
The good sleep
The findings suggest that taking regular naps is associated with locational awareness, verbal fluency, and working memory.
Sleeping patterns change as we age, the team explains, and most people take afternoon naps more frequently as they get older. However, we didn't know for sure whether this change could prevent cognitive decline and the risk of developing conditions such as dementia, or if it was a symptom of such cognitive decline.
Around 1 in 10 people over the age of 65 in the developed world will develop dementia, the authors note, so research such as this can help keep a lot of people mentally healthy.
The study worked with 2214 "ostensibly healthy" participants aged 60 and up, all of them residents in several large Chinese cities including Beijing, Shanghai, and Xian. Out of these, 1534 regularly took an afternoon nap, while 680 didn't. Both groups slept on average 6.5 hours per night, and all participants underwent a series of health checks and cognitive assessments beforehand to check for dementia. The test for dementia (Mini Mental State Exam, MMSE) included 30 items that measured several aspects of cognitive ability and higher functions such as visual and spatial skills, attention span, working memory, and verbal fluency.
Afternoon naps were defined as any period of at least five minutes but no more than 2 hours of uninterrupted sleep taken after lunch. Each participant was asked how often they napped during the week, ranging from once a week to every day. Nappers in the study showed significantly higher scores on the cognitive test than those who didn't nap. The most pronounced differences were in locational awareness, verbal fluency, and memory.
This was an observational study, so the findings aren't the be-all and end-all on the matter. Elements such as nap duration or timing were not taken into account, for example, and they could be very meaningful for the overall effect. At the same time, napping may not be the cause of the cognitive differences between participants. All we know so far is that they happened together in this group; more research is needed to understand what we're seeing.
However, the team does have some hypotheses it wants to test moving forward. One is that inflammatory chemicals, which play an important part in sleep disorders, are the link between poor health outcomes and mid-day naps. Sleep helps regulate our immune system and could be an evolved response to inflammation, as seen in patients with higher levels of inflammation.
The paper "Relationship between afternoon napping and cognitive function in the ageing Chinese population" has been published in the journal General Psychiatry.