Whether you find yourself sleeping much less or much more as you reach your middle ages, it could indicate that your brain is ageing prematurely.
A study attended by over 5,400 people aged 45-69 showed there was significant decline in brain power in those people, who had, over the course of a five-year period, changed the amount they slept from the optimum six to eight hours per night, reported The Guardian on its website.
"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 Jane Ferrie of the department of epidemiology and public health at University College London Medical School, who led the study.
The results are published in the May 1 edition of the journal Sleep.
The participants were asked about their sleeping habits in 1997-1999 to establish baseline numbers and again in 2002-2004 for a follow-up.
Their cognitive functions were monitored using a range of tests that included measurements of memory, vocabulary and reasoning.
They also carried out the mini mental state examination, designed to test for the early signs of dementia.
When compared with people whose sleep patterns had not changed since their baseline, those who had been sleeping more showed lower scores on five of the six cognitive function tests.