Sleep patterns often change as we age, with many older people adding an afternoon snooze to their daily schedule. The meaning of such naps has been unclear: Do they help keep the mind agile, or do they signify incipient dementia? A new study may have the answer.
Older people who take afternoon naps score more highly on cognitive tests than their non-snoozing contemporaries. These nappers exhibit stronger cognitive function, including memory, orientation, and language.
Disturbed sleep linked to dementia
People are living longer, with dementia affecting 5–7% of adults aged over 65 years worldwide, its diagnosis is a common occurrence. In Western countries, the rate of dementia is slightly higher at 8–10%.
Since there is currently no cure for dementia, there is clear value in identifying lifestyle changes that can help reduce the chances of developing the condition.
With disturbed sleep patterns having known associations with dementia, the role of napping in older cognitive health is an obvious area of interest. Unfortunately, previous findings have been inconsistent, say the authors of the current study.
For example, they cite 2012 research that found afternoon naps delay the onset of dementia, and yet another study concluding afternoon sleepiness may increase the risk of dementia or cognitive decline.
Studying napping patterns in older adults
The researchers studied 2,214 healthy people from several large Chinese cities, including Beijing, Shanghai, and Xian. All were at least 60 years old. The average night-time sleep interval of study participants was 6.5 hours.
To evaluate existing dementia, the researchers tested participants using the Beijing version of the Montreal Cognitive Assessment and the Mini-Mental State Exam (MMSE)
The team evaluated participants’ cognitive ability and higher function through 30 measurements of visual space, memory, naming, attention, calculation, abstract, orientation, and language function.
The researchers used the Chinese Neuropsychological Test Battery to measure “digit span, auditory verbal learning, associative learning, visual retention, language fluency, mapping, and a test with blocks.”
The researchers assessed all participants’ health while profiling their blood for cholesterol levels and triglyceride fatty acids, or “TG.” For the purposes of the study, the team defined a nap as anywhere from 5 minutes to 2 hours of sleep after lunch.
Of the group, 1,534 reported regularly taking an afternoon nap, with the frequency of their snoozes ranging from once a week to every day.
The study reports three main results:
- “First, the older individuals who took afternoon naps showed significantly higher cognitive performance compared with those who did not nap.
- Second, it was discovered higher levels of TG in napping older adults.
- Finally, afternoon napping was strongly associated with orientation, language function, and memory.”
The higher TG levels were within a normal range, and therefore may not have impaired cognitive function in the study’s participants.
However, the authors note that not all naps are alike. The study found that longer and more frequent naps tended to be associated with poor cognitive function.
Short and less frequent naps — lasting less than 30 minutes and occurring four times a week — appear to be the most helpful.
These naps lead to an 84% decrease in the chances of developing Alzheimer’s. In addition, people who deliberately nap, instead of simply dozing off in place, are more likely to acquire cognitive benefits.
The researchers suggest that their conclusions may differ from previous contrary research due to the differences in the napping styles studied. The current study is unique in investigating nap frequency.
Also, while some other studies looked primarily into different nap durations, the current research caps it at 2 hours. In addition, “they bring unintentional or intentional napping into analysis while we only assessed afternoon napping (i.e., post-lunch).”
