Dementia is a disorder that causes significant decline in cognitive function, impacting around 5%-7% of adults over the age of 65 in most regions of the world, and even more (8%-10%) in the developed countries. There is currently no effective treatment for dementia, however it’s occurrence in the elderly can be reduced by identifying and modifying risk factors such as physical inactivity, hypertension, obesity, and diabetes. It has been confirmed that disturbed night sleep is highly associated with an increased risk of cognitive decline and dementia.
With increasing age comes considerable changes to sleep patterns, and from a cultural perspective, afternoon napping is seen as part of a healthy lifestyle. Additionally, the occurrence of afternoon napping has been increasing in older adults much more than in younger individuals. As we all know, how we live our lives tremendously impacts the course of our cognitive function. Whilst more attention has been paid to napping recently, it remains controversial whether napping could benefit cognitive function or if it might be a risk factor for cognitive impairment in the elderly. For example, a study in 2012 indicated that daytime napping was associated with a lower risk of cognitive decline, whilst a different study showed an increased risk of dementia or cognitive decline associated with reported excessive daytime sleepiness. Now, it has been pointed out that napping might be useful as an early marker of cognitive impairment in the elderly, and its cognitive effects may differ by nighttime sleep. This current study explored the relationship of afternoon napping with cognitive function in a group of community elderly Chinese individuals.
In this study, afternoon napping was defined as periods of a minimum of 5 continuous minutes spent sleeping, but no more than 2 hours, after lunch outside of the main sleep schedule. A total of 2214 healthy individuals were included in this study, with 1534 nappers and 680 non-nappers. Nappers were also categorised by nap frequency: rarely (once a week), some days (1-3 times per week), most days (4 to 6 times per week), or every day (7 times per week). Participants also underwent several screening assessments, including cognitive assessments, and educational attainment was recorded (classified as illiteracy, primary school, junior high school, high school, or technical secondary school, university or above), amongst other components of lifestyle recorded. The data were then analysed with several specialised models and tests.
One of the ways that cognitive function was measured was with the Beijing version of the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE). These screening tests consisted of 30 items that measured multiple cognitive domains, including visual space, memory, naming, attention, calculation, abstract orientation, and language function. The MoCA test contained more attention-executive items than the MMSE. The MoCA is sensitive to detect mild cognitive impairment, and MMSE is suited to distinguish dementia. In both tests, the higher your score is, the better your cognitive function is deemed to be. The tests are also shown below for those of you who would like to give it a go!
The results showed that the MMSE scores were statistically higher in the napping group compared with the non-napping group. Additionally, the researchers also observed significant differences in orientation, language function in MMSE, and orientation in MoCA, with results showing that napping was associated with better cognitive function including orientation, language, and memory.
This study highlighted higher cognitive performance in elderly nappers, supporting previous observational studies. However, these benefits decrease as age increases. In addition to reducing sleepiness, mid-day naps offer a variety of benefits such as memory consolidation, preparation for subsequent learning, executive functioning enhancement and a boost to emotional stability, but these effects were not observed in all cases. Longer and more frequent naps were associated with poorer cognitive functioning, while short (<30 min), frequent (four times weekly) naps were associated with an 84% decreased risk for developing Alzheimer’s disease.
A number of factors, such as the timing, duration, frequency, and planned or unplanned nature of naps, need to be considered when determining the benefit of daytime napping, and so there’s still space for more studies to be carried out regarding these factors. It should be noted that this was an observational study and so is unable to establish cause, however, for the results of this study, the researchers have demonstrated that afternoon napping was associated with better cognitive function including orientation, language, and memory.
Original Source: , et al. (2021) “Relationship between afternoon napping and cognitive function in the ageing Chinese population
Original Link: https://gpsych.bmj.com/content/34/1/e100361.full
Edited by Cyrus Rohani-Shukla