Sleeping Less Than Six Hours, Or More Than Eight Hours, Bad For Middle-Aged

Less than six hours of sleep could prove too little for middle-aged. But more than eight hours could prove too much. Healthy cognitive function in later life could depend on the right sleep duration.
A study by researchers with the University College London Medical School Department of Epidemiology and Public Health shows that those without adequate sleep suffer accelerated cognitive decline. The findings have been published in the May 1 issue of the journal Sleep. 

Results show that the sleep duration at follow-up of 7.4 percent of women and 8.6 percent of men had increased from “7 or 8 hours” per weeknight at baseline. Compared with participants whose sleep duration was unchanged, this change to a longer sleep duration was associated with lower scores at follow-up on five of six cognitive function tests, with the only exception being the test of short-term verbal memory. The sleep duration at follow-up of about 25 percent of women and 18 percent of men had decreased from “6, 7, or 8 hours” per night at baseline. This change to a shorter sleep duration was associated with lower scores at follow-up on three of the six cognitive tests, with reasoning, vocabulary and global cognitive status all being affected adversely. Surprisingly, an increase in sleep duration from six hours or less showed no evidence of a beneficial effect.