Taking a regular afternoon nap may be related to better mental alertness, a study found. The researchers found that sleeping in the afternoon was associated with better locational awareness, verbal fluency and working memory in an aging Chinese population.
The study, published in an online newspaper General Psychiatry, examined the sleep patterns of 2,214 healthy people aged 60 and over in several major cities in China, including Beijing and Shanghai. Of those who participated in the study, 1,534 dozed off regularly in the afternoon, from five minutes to two hours, while 680 did not.
Study participants were asked how often they dozed off during the week, with responses ranging from once a week to every day. The average duration of night sleep was about 6.5 hours in both groups, although no information was collected on the specific duration or time of naps.
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All participants participated in a dementia screening test to assess their brain’s cognitive functions in a number of areas. This found “significant” differences in locational awareness, verbal fluency and memory, with higher scores between the group of naps.
“In addition to reducing sleepiness, midday naps offer a variety of benefits, such as memory consolidation, preparation for subsequent learning, improved executive functioning and increased emotional stability, but these effects were not seen at all cases ”, concluded the study.
However, the authors pointed out that research so far has not been able to conclude whether afternoon naps prevent dementia and cognitive decline in older people, or whether they may be a symptom of dementia.
Dr. Sara Imarisio, head of research at Alzheimer’s Research UK, said: “Scientists continue to work to unravel the relationship between sleep and dementia. Unusual sleep patterns are common for people with dementia, but research suggests that changes in sleep may be apparent long before any symptoms such as memory loss start to appear.
“In this study, scientists were unable to find out whether daytime napping directly affected memory and thinking, with the research only showing a connection between the two.
“While other studies have also indicated a link between changes in sleep quality, a larger study that looks at a number of factors related to sleep, not just naps, is needed to draw a clearer picture of the link between dementia and sleep to throughout the day. “
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Those who have a habit of napping in the afternoon also had a higher level of triglycerides, a type of fat found in the blood, than their colleagues who did not nap. Triglycerides can quickly cross the blood-brain barrier and interfere with other key proteins. It has been reported to induce leptin and insulin resistance, decreasing cognitive abilities.
Previous research has also linked napping to risk factors for cardiovascular disease, including age, triglycerides, blood pressure and glucose levels. Thus, these increased levels can be a negative indicator for cardiovascular disease and abilities. Although they were comparatively higher, triglyceride levels were still within the normal range, which the researchers suggest may be the reason why cognitive function was not negatively affected.
The increase in life expectancy and the associated neurodegenerative changes that come with it mean that there is an increase in the number of people diagnosed with dementia. Approximately 5 to 7 percent of people over 65 in the developed world have been affected by dementia.
The researchers said a theory that may explain their findings is that sleep regulates the body’s immune response and napping is believed to be an evolved response to inflammation. “Individuals with higher levels of inflammation also doze more often,” said the study.
They also noted that there was variation in the observed benefits that need to be investigated. For example, longer naps were associated with a decline in cognitive function, while shorter naps (less than 30 minutes) and more frequent naps were associated with a lower risk of developing Alzheimer’s disease.
The authors intend to continue their research to understand the details of these associations and hope to publish more works with this cohort in the future.
Reader Questions and Answers: Does dreaming affect the quality of our sleep?
Asked by: Ashley Martin, Hampshire
Research suggests that having frequent nightmares is associated with worse subjective sleep quality. Nightmares can cause anxiety, making it more difficult to go back to sleep or nap.
However, the connection between dream and sleep quality is twofold. We are more likely to remember a dream when we wake up from it; therefore, if we sleep poorly and wake up several times during the night, we are more likely to remember the content of our dreams.
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