Many factors comprise a person's cognitive abilities and IQ score. In fact, new research suggests that changes in sleep can affect cognitive function in later life.

For the study, which is published in the journal Sleep, scientists analyzed 5,431 participants - 1,459 of whom were women and 3,972 were men. They found that those who began sleeping more or less than six to eight hours per night over a five-year period had accelerated cognitive decline that equated to aging between four and seven years.

About 7.4 percent of female participants experienced increases in sleep duration during the study, which was linked to lower scores on five of six cognitive tests. Male volunteers reported similar changes.

"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, lead researcher and senior research fellow in the University College London Medical School Department of Epidemiology and Public Health in the U.K.

The study also revealed that the optimal level of sleep for women is seven hours per night, and between six and eight hours for men.