Sunday, January 24, 2021

Have women been missing out on chances to maintain cognitive reserve?


At present, the majority of people with late-onset Alzheimer's disease are women. While there are a variety of reasons why this may be the case, one possible factor is reduced opportunity to maintain cognitive reserve. (Although it has been defined in subtly different ways, cognitive reserve is essentially the maintenance of cognitive performance in the presence of brain pathology due to a "bank" of greater cognitive resources over the lifespan, such as formal education or an intellectually stimulating job). For example, some women may have (or have had) less cognitive reserve if they have left formal education earlier. 

A recent review paper has looked at this in depth. The authors highlight that much of the evidence that has been used to propose models of cognitive reserve has not looked at whether these models hold to the same extent for men and women, and so there may be underappreciated sex differences. Nonetheless, the authors did identify a number of studies that did grapple empirically with sex differences and cognitive reserve. (Although sex and gender are not the same thing, the authors noted that some studies referred to sex and others to gender, and sex differences may be conflated with gender roles; overall, it was unclear whether existing data would allow anyone to tease apart sex differences and gender differences).    

Focusing on education in particular, the authors found two longitudinal studies that indicated that more years of education led to reduced incidence/prevalence of Alzheimer's disease, and this effect did not differ between the sexes, although two other studies found that years of education were correlated with reduced Alzheimer's risk, but only for women. So it would seem the studies did agree that education reduced Alzheimer's risk for women, although the evidence was more equivocal for men (one might speculate that perhaps young males are more likely to enter more cognitively stimulating work if they leave school early, compared to young females, or at least this has been the case in the recent past). 

However, a cross-sectional study found that men with Alzheimer's disease had better performance on the MMSE than women of the same age with the same level of education, suggesting reserve was more beneficial for men (the authors of the review point out that this study did not assess neural pathology, so it may be the case that the women in this study had more advanced neural pathology than the men).   

Although I've briefly focused on education and women in particular above, it is likely that people from various disadvantaged groups have less opportunity to develop cognitive reserve over their lives. Internationally, there are substantial differences in the average number of years people spend in formal education, and although great progress has been made globally in closing the gender gap over the last century, the female:male ratio for years of schooling is still around 85% for Asia, Africa and the Pacifics. The full paper below looks in more detail at other factors that can help to maintain cognitive reserve:

Subramaniapillai, S., Almey, A., Rajah, M. N., & Einstein, G. (2020). Sex and gender differences in cognitive and brain reserve: Implications for Alzheimer’s disease in women. Frontiers in Neuroendocrinology, 100879.

 Related posts

Conference review: Reserve and resilience

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