As well as drawing the short straw in the childbirth department – it seems that the bad hand dealt to women by mother nature doesn’t end with the menopause. Women are twice as likely to suffer from dementia as men – with two-thirds of sufferers being women. This can partially be attributed to the fact that women live longer but there is new US based research that has now linked the increased development of dementia to those who have shorter reproductive windows. The observational study, based on close to 16,000 women, found that women who started having their periods later than average, or had a hysterectomy/went through the menopause earlier than average, were more likely to develop dementia than women who experienced these life events at average ages.
The researchers believe that this may be due to reduced exposure to oestrogen which could potentially contribute to the development of cognitive decline. Laboratory research initially suggests that oestrogen aids resiliency and repair of brain cells. This correlates with the previous evidence that concludes greater lifetime exposure to oestrogen might be ‘better’ when it comes to brain function. However this can’t prove conclusively that the lack of oestrogen can cause dementia – there could yet be other explanations for the link.
The brain controls the release of hormones, so it is possible that women who started their periods later or ended earlier, simply have different aspects of their brain function which is what causes the prevalence of dementia. The study didn’t track the effect of hormone therapy given after the menopause, record hormone levels or look at other factors that could influence oestrogen levels so there is still a lot more to discover when it comes to female brain function. For example, the number of children a woman has had and whether she breastfed are also important factors. The University of Cambridge has already discovered a ‘highly significant and consistent correlation’ between breastfeeding and Alzheimer’s. Mothers who breastfed their children had a lower risk of developing the disease as opposed to those who hadn’t, with longer periods of breastfeeding also lowering the overall risk. This is thought to be due to the biological effect of breastfeeding, as it restores insulin tolerance after pregnancy, and Alzheimer’s is characterised by insulin resistance in the brain. The number of children a woman has could also be pertinent as more studies in the US concluded that women with three or more children had a 12 percent lower risk of dementia compared to those with only one child.
So what does this mean for the future? Well it could be a great place to start when investigating possible medical intervention – it may be that women who go through early menopause are given targeted hormone therapy for example. However more investigation is needed. Previous research found that oestrogen and progesterone therapy actually increased the risk of dementia in postmenopausal women 65 years and older, however had no negative cognitive effect in women who had started hormone therapy between the ages 50 and 54 – so it is obvious that timing is critical and that hormone therapy is not a cure-all.
It is clear that the hormone factor is just one piece of the puzzle when it comes to discovering why some women develop dementia and why it is more prevalent in women. Luckily, the charity Alzheimer’s Research UK is funding research at the University of Cambridge to further investigate why women have a greater risk of dementia than men so that sometime soon, we will start to fill in more of the missing pieces and gain greater knowledge and clarity on this complex area of human biology.