Extreme sleep durations, such as sleeping too much or too little, may affect brain health later in life, according to a recent study Counsel and Heal reported.

Researchers from Brigham and Women's Hospital found that women who sleep for less than five hours per day, or more than nine hours per day, had worse memory, equivalent to nearly two additional years of age, than those sleeping seven hours per day.

They also found that Women whose sleep duration changed by greater than two hours per day over time had worse memory than women with no change in sleep duration.

"Given the importance of preserving memory into later life, it is critical to identify modifiable factors, such as sleeping habits, that may help achieve this goal," Elizabeth Devore, lead author of the study, said in a statement. "Our findings suggest that getting an 'average' amount of sleep, seven hours per day, may help maintain memory in later life and that clinical interventions based on sleep therapy should be examined for the prevention of cognitive impairment."

For the study, researchers collected data from more than 15,200 participants of the Nurses' Health Study. The participants were female nurses, aged 70 or older and were free of stroke and depression at the initial cognitive assessment.

Based on their findings, extreme sleep durations may adversely affect memory at older ages, regardless of whether they occur at mid-life or later-life. They also found that women with sleep durations that changed by two or more hours per day from midlife to later life performed worse on memory tests than women with no change in sleep duration, equivalent to being one to two years older in age, compared to those whose sleep duration did not change during that time period.

"These findings add to our knowledge about how sleep impacts memory," Devore said. "More research is needed to confirm these findings and explore possible mechanisms underlying these associations."

The findings were recently published in The Journal of the American Geriatrics Society.