A new observational study is building on an increasing body of data finding a correlation between afternoon naps and improved mental agility and cognitive function. The research hypothesizes afternoon naps may help moderate age-related neuroinflammation, helping keep the brain healthy.
The new research recruited more than 1,500 elderly subjects, all self-reported afternoon nappers. For the purposes of this study, afternoon naps were defined as short periods of sleep after lunch lasting longer than five minutes and no more than two hours. An age-matched control group of more than 600 non-nappers were also recruited.
“In this study, three major findings were presented,” the researchers write in the study. “First, the elderly individuals who took afternoon naps showed significantly higher cognitive performance compared with those who did not nap. Second, higher levels of TG [triglycerides] were found in napping elderly individuals. Finally, afternoon napping was strongly associated with orientation, language function and memory.”
Both the control group and the nap group reported an average of 6.5 hours of sleep per night. This is important to note since it makes clear the daytime nappers were not compensating for disruptions to overnight sleep but instead complementing that rest with extra daytime slumber.
The researchers are clear to note that not all daytime naps are beneficial. In fact, the science of sleep is often contradictory. Long daytime naps have been linked to increased risk of stroke and higher rates of all-cause mortality.
“On the one hand, daytime sleep is beneficial to the recovery of the immune system, while naps and night sleep promotes immune repair,” the researchers write in the study. “On the other hand, frequent daytime sleep is associated with the immune decline in both the young and the elderly.”
Prior research has clearly found excessive sleep in the elderly can be associated with the onset of Alzheimer’s disease and neurodegeneration. So, to best ascertain whether one’s napping habits are helping or hindering general health, broad sleeping behaviors must be taken into account.
“…most studies that reported negative effect of napping on cognitive function focused on the napping duration,” the researchers write. “Those who napped more than 2 hours are more likely to show worse cognitive functions. The napping duration of the elderly in our research did not exceed 2 hours, which could also be a reason why we came to different conclusions.”
This new research does not offer evidence of a causal relationship between afternoon naps and brain health. However, it does hypothesize the mechanisms that could underpin this association.
Perhaps the most convincing hypothesis comes from the known link between inflammation and sleep disorders. The researchers suggest sleep helps the body regulate its inflammatory responses, which is why individuals with high levels of inflammation have been found to nap frequently.
“In the elderly, sleep disorders or sleep deprivation at night are caused by increased levels of IL-6 and C reactive protein, the release of inflammatory transmitters, promotion of oxidative stress and accumulation of reactive oxygen species,” the researchers suggest in the study. “At the same time, high levels of inflammatory responses lead to adverse events, such as cognitive impairment and increased mortality. Sleep is known to be a regulator of the immune response that counters these inflammatory mediators, where napping, in particular, is thought to be an evolved response to inflammation.”
The new study was published in the journal General Psychiatry.
Source: BMJ
