The commonly held explanation has been that women live longer than men and have more time to develop the degenerative brain disease that can come with old age.
Now researchers say that may not be true, and they are finding other explanations.
One theory involves women’s brains, which appear to have higher connectivity among the areas where a toxic protein called tau can build up. The accumulation of tau, a characteristic of Alzheimer’s, causes brain cells to die.
Researchers at the Vanderbilt University Medical Center found the connectivity in women’s brains linked together areas where tau tended to develop, allowing the destructive protein to spread more quickly.
“The majority of people living with Alzheimer’s are women, and it’s imperative we understand why,” said Maria Carrillo, chief science officer at the Chicago-based Alzheimer’s Association. “Alzheimer’s is different in men and women.”
The latest research was presented this week at the Alzheimer’s Association International Conference in Los Angeles.
One study looked at heart disease, which has been linked to Alzheimer’s. It suggested that because men are more likely to die of cardiovascular disease in middle age, those who live past age 65 may have healthier hearts, putting them at a lower risk of dementia than women of the same age.
Epidemiologists caution that the findings showed a “survival bias” because the men who are studied are those who live longer and thus tend to be the healthiest.
Another study found certain genes specifically in men or in women could be linked to the risk and progression of Alzheimer’s and symptoms of memory decline and dementia.
Under investigation is a theory that one gene in particular associated with Alzheimer’s may raise the risk for women because of the way it interacts with estrogen.
Earning a paycheck helps
But the research held out some hopeful news as well.
Women who worked outside the home between ages 16 and 50 had better memories than those who did not, said a study of nearly 7,000 women born between 1935 and 1956.
Women over age 60 who had been in the paid labor force experienced slower memory decline, it said. Memory deterioration was most rapid among women who never did paid work.
“Though preliminary, our research provides evidence that participation in the paid labor force may help prevent late-life memory decline among women in the United States,” said UCLA researcher Elizabeth Rose Mayeda.
While it did not delve into the reasons, the researchers suggested the mental stimulation, social atmosphere and financial benefits of paid work could be factors.
Another study found white adults who often took sleep medication were 43% more likely to develop dementia than those who rarely or never took sleep aids.
Several studies have shown the incidence of Alzheimer’s in the United States and other Western countries may have dropped in the past 25 years, in part due to people taking better care of their hearts’ health.
But worldwide increases in obesity and diabetes, both risk factors for Alzheimer’s, threaten to bring a rebound in the disease, research said.