July 16, 2012 -- Getting a recommended seven hours of sleep a night may help women keep their memory sharp, suggests a new analysis of data from the Nurses' Health Study.
The study found that women who slept five hours or less on average per day had lower scores on standard memory tests than those who slept seven hours, reports Elizabeth Devore, ScD, of Brigham and Women's Hospital in Boston.
Similarly, women who slept nine or more hours on average per night had lower memory scores than those who slept seven hours a night, Devore tells WebMD.
"Women who got too little or too much sleep had the memories of women about two years [their senior]," she says.
The link between sleep duration and memory held true both in mid-life and later life, Devore says.
The findings were presented in Vancouver at the Alzheimer's Association International Conference.
Many Don't Get Enough Sleep
A recent CDC study found that more than 40 million workers get less than six hours of sleep per night.
So the researchers examined data for more than 15,000 participants in the Nurses' Health Study. The women answered questions about how many hours they slept a night both in 1986 (when they were aged 40 to 65) and in 2000 (when they were aged 54 to 79).
Then, between 1995 and 2000, when the women were aged 70 or older, they took a series of memory tests. Follow-up memory tests were conducted every other year for six years.
"Interestingly, women whose sleep changed by two or more hours per day on average from mid- to later life had worse memory than those with no change in sleep duration, independent of their initial sleep duration," Devore says.