60% of dementia patients women
New research suggests hormones, number of pregnancies could have a role
Women make up 60 per cent of Alzheimer’s disease patients in the United States, and over her lifetime, a woman is almost twice as likely as a man to develop the memory-robbing condition.
New research offers tantalizing clues as to why that might be, suggesting that either hormonal influences or pregnancy-related changes in the immune system — or both — may nudge a woman’s risk for dementia in one direction or the other.
In a comprehensive study that tracked almost 15,000 U.S. women from middle age into their senior years, researchers found that women who gave birth to three or more children were less likely than those who had a single child to develop dementia.
Reporting their findings Monday, the authors of the new research said also that women whose lifetime span of fertility was shorter appeared more likely to develop dementia than were those who began menstruating earlier.
The new findings, reported at the Alzheimer’s Association’s International Conference in Chicago, offer an early clue that hormones, specifically estrogen, may exert some influence on a woman’s risk of dementia. They emerged from the first study to explore women’s lifetime dementia prospects by tracking a very large group of women over a long period — for some, as long as 53 years.
In other research presented Monday, a pilot study that captured the pregnancy histories of 133 British women offered evidence that a female’s likelihood of developing dementia declined as the number of months she had spent pregnant rose.
In many ways, those findings are consistent with the study suggesting a hormonal influence on dementia risk in women. But the author of the pilot study, UCLA anthropologist Molly Fox, said her findings suggest another influence on a woman’s dementia risk — the profound changes in the immune system wrought by pregnancy.
Collectively, the new research marks a first-ever effort to explore the underpinnings of gender differences in dementia. That effort is certain to uncover insights into the factors that influence the risk of cognitive decline as we age, and possibly ways to counter that risk in both men and women.
For decades, researchers presumed that women were more likely than men to develop dementia because they are more likely than men to survive into old age. As a disease of aging, their reasoning went, dementia is more likely to affect the longer-lived sex.
By suggesting possible roles for hormones and the immune system, the new research has offered some intriguing alternative hypotheses: that women, who evolved to spend much of their fertile years in pregnancy, might long have accrued protections against dementia equal to a man’s. But as families have become smaller, women have lived longer, and their reproductive years have come to account for a smaller share of their lives, it’s possible that women’s dementia risk has risen.
That the female hormone estrogen is at work is suggested by several of the large study’s findings. From 1964 to 1973, the undertaking enrolled female members of Kaiser Permanente ages 40 to 55.
Researchers initially collected data on the number of children the women had birthed, how many miscarriages they had suffered, and the ages at which they began and ceased to menstruate.