There has been for many decades a discussion as to whether women might be at a higher risk to develop dementia compared to men. The original notion for this idea came with the insight that more women than men were diagnosed with dementia and Alzheimer’s disease.
Epidemiologist [scientists specialised in health on a population level], however, pointed quickly out that women are on average having a higher life expectancy than men. Indeed, the average life expectancy for women and men in the UK today is 82.9 years and 79.3 years, respectively. Basically, women life nearly 3 years – on average – longer than males. The reasons for this increased longevity are still being explored, however, the difference has also implications for dementia prevalence [prevalence = how common dementia is in the general population].
We know that the biggest risk factor for dementia is age. This means the older we get, the more likely we are to develop dementia. No wonder the epidemiologists pointed out that if women get on average older, then there should be a higher number of women affected by the disease. This would also mean that women are not at higher risk of developing dementia than men in general, instead, they are simply getting older which increases their risk for dementia. However, even after statistical models were corrected for the greater longevity in women, many studies have found that women are still at a higher of dementia compared to men.
What might be the cause for this difference?
Several theories have been proposed and the emphasis is clearly on ‘theories’, as there is no definitive scientific proof as to why women are more prone to develop dementia than men. Still, there is one obvious factor which distinguishes women and men and has been of particular focus for these scientific investigations – estrogen.
Estrogen is a sex hormone which is found in higher levels in women than men and determines part of women’s menstrual cycle. But hang on, should older women at the age of dementia not have had their menopause, which should have reduced their estrogen? Exactly!
It is in fact less estrogen in the body which has been associated with an increased risk of dementia. We also know that dementia takes a long time to establish itself in the brain, so after women are through the menopause, this can lead years or even decades later to dementia. Importantly, some studies have shown that women who are on Hormone Replacement Therapy (HRT) after their menopause do not have an increased of dementia. The reason is that they keep their estrogen levels high by taking HRTs.
Why is estrogen so important for development of dementia?
The short answer is that we do not know at this stage what the actual mechanism is for estrogen to provide some form of protection against dementia. However, what is known is that estrogen has some neuroprotective mechanisms in the brain. Neuroprotection means that estrogen helps to protect the nerve cells, which might therefore also protect the nerve cells from developing dementia.
Does this mean all women should consider being on HRTs post-menopause to reduce their risk of dementia?
This is an interesting question and the answer is not clear. We need to point out that although some studies have shown that HRT can reduce the risk of dementia in women, other studies have shown no such effect. It seems, therefore, as always, that the issue is more complex than previously thoughts. This is, therefore, further under scientific investigation.
Still, the overall impact of the menopause and its reduction in estrogen highlights again that events in mid-life – such as the menopause – can have a potential long-term effect for dementia development in late-life.
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