Too Much or Too Little Sleep Accelerates Cognitive Aging

New research suggests that changes in sleep that occur during late middle-age appear to have a significant effect on cognitive function later in life. Jane Ferrie, a senior research fellow at University College London Medical School in the UK, and colleagues studied data from 5,431 people taking part in the on-going Whitehall II study of more than 10,000 office staff aged 35-55, which began in 1985. Normal sleep duration was measured during Phase 5 (1997-1999) and Phase 7 (2003-2004) of the study. Results showed that 7.4% of women and 8.6% of men reported sleeping for longer than the 7-8 hours reported at Phase 5. In comparison with participants whose sleep duration had not changed, this increase in sleep duration was associated with lower scores at follow-up on five out of six cognitive function tests. On the other hand, 25% of women and 18% of men reported sleeping for less than the “6, 7, or 8 hours” reported at Phase 5. This shift was also associated with a decline in cognitive function, with participants scoring lower at follow-up on three out of six cognitive function tests. Results also showed that, for women, 7 hours of sleep per night was the most beneficial in terms of cognitive function, closely followed by 6 hours of sleep per night. For men, 6-8 hours was optimal. The researchers concluded that their findings suggest that women and men who begin sleeping more or less than 6-8 hours per night are subject to an accelerated cognitive decline that is equivalent to four to seven years of aging. "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," said Ferrie. "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."