Not only do women live longer than men, on average, but a new study from the Mayo Clinic suggests they also may keep their cognitive function longer, too.
In a study of more than 2,000 adults 70 to 89 years old, researchers found that men were 1.5 times more likely to experience mild cognitive decline than their female counterparts.
Researchers tested elderly men and women in Olmstead County, Minn., for signs of mild cognitive impairment (MCI), a condition in which people have problems with memory or thinking beyond the decline seen because of normal aging. MCI can be a pre-cursor to Alzheimer's disease or other forms of dementia.
Because some, but not all, patients with MCI go on to develop Alzheimer's, understanding how MCI develops and how it affects the population is integral to early detection of dementia and Alzheimer's specifically says the lead author on the study, Dr. Ronald Petersen of the Mayo Clinic in Rochester, Minn.
Though past research shows that women are more likely to suffer from Alzheimer's in their lifetime, researchers found that there were significantly more men experiencing the early stages of cognitive decline: 19 percent of men had MCI whereas only 14 percent of women did.
When MCI and dementia are taken together, a quarter of the study population was in some state of cognitive decline, a statistic that Petersen believes highlights the public health impact of the conditions and the importance of finding treatments for them.
Why might men decline earlier only to have a lower precedence of Alzheimer's?
It may have to do with the progression of cognitive decline, says Petersen.
"Men may experience cognitive decline earlier but stay in that stage longer, while women don't see cognitive impairment until later in life but have an abrupt decline into dementia," he says.
A popular explanation for the overall gender difference seen in Alzheimer's rates is life span, says Dr. William Thies, chief medical and scientific officer of the Alzheimer's Association.
"Women typically live longer than men and, therefore, are more likely to live through mild cognitive impairment and go on to develop Alzheimer's disease," he says.
Therefore, the men still living and able to be measured by researchers would be more likely to be in the early stages of the disease.
Heart disease also may play a role, according to Dr. Gary Kennedy of the Montefiore Medical Center.
"Because vascular diseases often accompany and exacerbate Alzheimer's disease, one would expect early signs of dementia such as MCI among persons with more vascular disease, namely men," he says.
There is little research on MCI and how it affects the elderly population, Petersen says, but it may become increasingly important as the field focuses on earlier and earlier detection of Alzheimer's disease.
"Can we pick up people at this memory impaired stage and determine which will go on to have Alzheimer's? This would allow us to intervene with treatment as early as possible and hopefully have a greater response to treatment," he says.
But while understanding MCI may help researchers understand the progression and gradations of Alzheimer's, the gender connection is "by no means definitive" at this point, notes Dr. Gregory Jicha, clinical core director of the University of Kentucky Alzheimer's Disease Center.
The study's sample, which drew from a largely Caucasian population, is also not generalizable to the general U.S. population.
"Overall, the risks for MCI are much stronger for age [and] education ... than they are for gender," he adds.
The fact that, regardless of gender, one in four elderly citizens in the population had impairments in memory and other cognitive function, highlights how important it is for researchers to better understand cognitive decline, experts say.