Taking a regular afternoon nap may be linked to better mental agility, a study has found.Researchers found sleeping in the afternoon was associated with better locational awareness, verbal fluency and working memory in an ageing Chinese population.
The study, published in online journal General Psychiatry, examined the sleep patterns of 2,214 healthy people aged 60 and over in several large cities in China, including Beijing and Shanghai.Of those who took part in the study, 1,534 took a regular afternoon nap of between five minutes and two hours, while 680 did not.
Participants in the study were asked how often they napped during the week, with answers ranging from once a week to every day.The average length of nighttime sleep was around 6.5 hours in both groups, though no information was taken on the specific duration or timing of the naps taken.
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All participants took part in a dementia screening test to assess their brain's cognitive functions across a number of areas. This found “significant” differences in locational awareness, verbal fluency and memory, with scores higher among the napping group.
“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,” the study concluded.
However, the authors did point out research to date could not conclude whether afternoon naps stave off dementia and cognitive decline in older people, or whether they might 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 sleep changes could be apparent long before any symptoms like memory loss start to show.
“In this study, scientists were unable to find out whether daytime napping directly affected memory and thinking, with the research merely showing a link between the two.
“While other studies have also indicated a link between changes in sleep quality, a larger study looking at a number of sleep-related factors, not just napping, is needed to paint a clearer picture about the link between dementia and sleep throughout the day.”
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Those in the habit of afternoon napping were also found to have a higher level of triglyceride, a type of fat found in the blood, than their non-napping counterparts. Triglycerides can rapidly cross the blood-brain barrier and interfere with other key proteins. They have been reported to induce leptin and insulin resistance, decreasing cognitive abilities.
Previous research has also linked napping with cardiovascular disease risk factors including age, triglycerides, blood pressure and glucose levels.Thus, these increased levels may be a negative indicator for cardiovascular disease and abilities. Although they were comparatively higher, the triglycerides levels were still within the normal range which researchers suggests may be why cognitive function wasn't negatively impacted.
Increase in life expectancy and associated neurodegenerative changes that come with it means there is an increase in people being diagnosed with dementia. Approximately 5-7 per cent of people over the age of 65 in the developed world have been affected by dementia.
Researchers said one theory which may explain their findings is that sleep regulates the body’s immune response and napping is thought to be an evolved response to inflammation.“Individuals with higher levels of inflammation also nap more frequently,” the study said.
They also noted that there was variation within the benefits observed which need to be further investigated.For instance, longer naps were associated with a decline in cognitive function, while shorter (less than 30 minutes) and more frequent naps have been linked to 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 work with this cohort in the future.
Reader Q&A:Does dreaming affect the quality of our sleep?
Asked by: Ashley Martin, Hampshire
There’s research to suggest that having frequent nightmares is associated with poorer subjective sleep quality. Nightmares can cause anxiety, making it more difficult to fall back to sleep, or nod off in the first place.
However, the link between dreaming and sleep quality goes both ways. We are more likely to remember a dream when we’re woken from it, so if we sleep badly and have multiple wakings during the night, we may be more likely to recall the content of our dreams.
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