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The report also concluded that almost two thirds of Americans with Alzheimer’s disease are women. Another way of looking at this is that Alzheimer’s disease is twice as likely in women over 65 compared to breast cancer.
In 2012, the Australian Institute of Health and Welfare released a report ‘Dementia in Australia’ which found similarly that approximately two thirds of people with dementia in Australia are women. However, the Australian report did vary in results when age groups were further divided. For example, more men under 65 had dementia (53% of cases), but far more women over 85 had dementia (close to 75%).
With this new Alzheimer's Association report receiving a lot of global media attention, Dementia News investigates why women have a greater risk of dementia than men. There are three main hypotheses, as follows.
Hypothesis 1: On average, women survive longer then men and are therefore more likely to develop dementia.
The Alzheimer's Association report references a large population based study, published in 2013 in the Journal Neurology. It was found that of the estimated five million people aged 65 and older with Alzheimer’s in the USA, 3.2 million were women and 1.8 million were men. The Alzheimer's Association report states that the observation that more women than men have Alzheimer’s disease and other dementias is primarily explained by the fact that women live longer, on average, than men, and older age is the greatest risk factor for Alzheimer’s. However, a 2001 study published in the American Journal of Epidemiology followed just over 1,000 participants aged over 65 in the city of Boston, USA. Although the study found that their was no difference between men and women in the risk of dementia at any given age, the fact that women lived longer than men resulted in women having a higher overall risk of having dementia, or developing the condition during the study period.
Scientia Professor Henry Brodaty – Director of the Dementia Collaborative Research Centre – Assessment and Better Care, and Chair of the Alzheimer’s Australia Dementia Research Foundation also agreed.
“It could be put down to simple maths – women live, on average, six years longer then men – which could be increasing their risk of developing dementia.”
While the age hypothesis, is certainly a valid one, many scientists believe that there are other factors at play.
Hypothesis 2: More men die from cardiovascular disease before 65 compared to women.
The Alzheimer’s Association report refers to a study published in the Journal Alzheimer’s and Dementia which suggests more men die from cardiovascular disease between the age of 45-65 compared to women. As with the first hypothesis, this would effectively mean that fewer men than women live to very old ages, at which the likelihood of developing dementia is much greater. The Australian Institute of Health and Welfare released a report in Australia in 2011 which found that the rate of cardiovascular disease in men was higher than in women across all age groups, with males aged 45–64 years experiencing death rates almost three times as high as those for females of the same age.
Hypothesis 3: Women have different hormonal physiology which may affect the risk of developing dementia.
Age-related reduction in levels of sex steroid hormones (which include testosterone, oestrogen, progesterone and others) has been established as a risk factor for Alzheimer's disease in both women and men. A review in the Journal Hormones and Behavior published in February 2013 suggested that oestrogen and testosterone regulate key processes implicated in Alzheimer’s disease, in particular the accumulation of amyloid beta protein. Because sex steroid hormones decrease more rapidly in women (after menopause) than they do in men, it is possible that dementia risk increases more dramatically in post-menopausal women than in men of the same age.
However, recent evidence has cast some doubt on this hypothesis. First, a study published in the Journal Neurology earlier in the year showed that diabetic women with high oestrogen levels were almost 14 times more at risk of dementia compared to those with low oestrogen levels who didn’t have diabetes. This shows that low oestrogen levels may only have a very small impact on overall dementia risk compared to other factors. In addition, trials of hormone replacement therapy as a treatment for Alzheimer’s disease has yet to be proven effective in any clinical trial. Many scientists are still trying to understand the roles that hormones play in cognitive function.
While it is clear that more women develop Alzheimer’s disease and other dementias than men in later life, the reasoning behind this is still unknown and much more research is required to fully understand why.
For more information on reducing your risk of dementia visit the Alzheimer’s Australia risk reduction website www.yourbrainmatters.org.au
Alzheimer’s Association Report - http://www.alz.org/alzheimers_disease_facts_and_figures.asp
AIHW Dementia in Australia - https://www.aihw.gov.au/publication-detail/?id=10737422958
Neuroepidemiology - http://www.ncbi.nlm.nih.gov/pubmed/17975326
Americal Journal of Epidemiology - http://aje.oxfordjournals.org/content/153/2/132.long
Alzheimer’s and Dementia - http://www.ncbi.nlm.nih.gov/pubmed/24418058
Hormones and Behavior - http://www.sciencedirect.com/science/article/pii/S0018506X12001134
Channel 7 News story - http://au.news.yahoo.com/nsw/video/watch/22080150/alzheimer-s-warning-fo...
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