“In comparison to 50, which is the average age of menopause, if you have it before the age of 47 [the risk] is 1.32 times higher, ”Gong explained. “Having your uterus removed versus not having your uterus removed is 1.12 times higher.”
Starting your first period before the age of 12 increased the risk of dementia later in life by 1.2 times compared to starting your first period at 13, which is about the average age of girls in Australia start menstruation.
But, the strongest risk factor was a younger age at the first live birth. “If you had birth before the age of 21 compared to 25 or 26 it’s about 1,436 times higher [risk]”Gong says.
During pregnancy, the primary form of estrogen is estriol, not estradiol, which is the form typically known to be neuroprotective. But, Gong says, estrogen levels may not explain the risk associated with giving birth at a younger age: “It may be possible that having children at a younger age (where the association with dementia is the strongest) are linked to other socioeconomic factors and behavioral changes. ”
Associate Professor Fiona Kumfor, a clinical neuropsychologist from the University of Sydney, says that although the role of estrogen levels in the development of dementia is increasingly being considered by researchers, it is still in its early days.
“Acknowledging and investigating sex differences is important as we still understand little about what causes dementia, but it is likely to be complex and multifactorial,” says Kumfor, who was not involved with the study.
What that means is that just because you get your first period before 12, if a hysterectomy or early menopause doesn’t mean you will get dementia later in life, explains Associate Professor Genevieve Steiner-Lim, an NHMRC Emerging Leadership Fellow at the NICM Health Research Institute.
Gong stresses that it is an observational study and some aspects were self-reported, meaning people may have Forgotten exact timings or other influencing factors: “We always talk about nature versus nurture.”
Childhood trauma, socioeconomic status and even where you live and your access to gyms, public pools, green spaces and health care as well as air pollution, all contribute to risk.
But although the study findings might seem “quite scary” because we have little control over them, Gong says she doesn’t want women to worry.
Rather, the point of the research is to recognize the sex-specific risk for dementia and “ensure the future strategies are sex- and gender-sensitive, to promote health equity,” she says.
For instance, Kumfor says: “Understanding if and how premenopausal hormone use (eg, via the pill) and hormone replacement therapy impact on later risk or prevention of dementia is an active area of research.”
Still, there are many things we can do to reduce our dementia risk. These include physical activity, not drinking alcohol excessively, quitting smoking, controlling our blood pressure, cholesterol and weight all well as regular social contact with others.
“We know something between 40 and 50 per cent of our dementia risk is modifiable and goes beyond our Biological sex and reproductive events in life,” says Steiner-Lim. “There are so many things that are within our control.”
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