Too much or too little sleep may accelerate cognitive aging and hurt brain performance
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Research has found that changes in sleep duration resulting in sleeping more or less than 6 to 8 hours per night is associated with a faster decline in cognitive ability for both women and men.
This decline is roughly equal to four to seven years of aging.
The researchers used data for 5,431 participants (1,459 women and 3,972 men) from the Whitehall II study of more than 10,000 London-based office staff working in 20 civil service departments.
The study looked at changes in sleep over a 5 year period.
Six standard tests were used to measure memory, reasoning, vocabulary, phonemic fluency, semantic fluency, and global cognitive status.
Results for both male and female subjects showed that, when compared with participants with unchanged sleep duration:
- Increases in sleep from 7 or 8 hours a night were associated with lower scores on 5 of 6 cognitive tests (the only exception being the test of short-term verbal memory);
- Decreases in sleep from 6, 7, or 8 hours a night were associated with lower scores on 3 of the 6 cognitive tests (reasoning, vocabulary and global cognitive status all declined)
- An increase in sleep duration from 6 hours or less showed no beneficial effect.
For women, sleep duration of 7 hours of sleep per night was associated with the highest score for every cognitive test. This was closely followed by 6 hours of sleep per night.
For men, only short and long sleep durations of less than 6 hours or more than 8 hours were associated with lower cognitive test scores. Sleep duration of 6, 7 or 8 hours showed similar unchanged cognitive test scores.
The lead author Jane Ferrie, PhD, senior research fellow in the University College London Medical School Department of Epidemiology and Public Health in the U.K. said:
The main result to come out of our study was that adverse changes in sleep duration appear to be associated with poorer cognitive function in later-middle age.
Given that our 24/7 society increasingly impinges on the lives of many people, it is important to consider what effects changes in sleep duration may have on health and well-being in the long term.
The researchers adjusted for the effects of education and occupational position due to their known association with cognitive performance.
According to the authors, adequate, good quality sleep is fundamental to human functioning and well-being.
Sleep deprivation and sleepiness have adverse effects on performance, response times, errors of commission, and attention or concentration.
Furthermore, sleep duration is associated with a range of quality of life measures, such as social functioning, mental and physical health, and early death.
The study was published in the journal Sleep (Ferrie et al., 2011).
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