As men age, their brain volume shrinks more significantly, and in more brain regions, than women. This is what a study published Monday October 13 shows in Proceedings of the National Academy of Sciences. But above all, report Nature, “For the authors, this reveals that changes in the brain linked to aging do not explain why Alzheimer’s disease is more often diagnosed in women than in men”.
Considering that Alzheimer’s disease was diagnosed about twice as often in women as in men, that the main risk factor was aging and that those affected suffered atrophy of certain brain regions, the researchers wanted to explore the trail of age-related differences in the brain depending on sex.
As early as 1998, work suggested that men’s brains tend to shrink faster than women’s. But other studies of aging-related gender brain differences have failed to provide a clear picture. Some found that men experienced more gray matter loss than women while others reported the opposite.
A complex cognitive disorder
For this new work, researchers reviewed more than 12,500 magnetic resonance imaging (MRI) images – taken several years apart – of the brains of 4,726 people aged 17 to 95 who did not have any dementia or cognitive impairment. The analysis of these MRIs notably made it possible to note that the part of the cortex responsible for processing the sensations of touch, pain and temperature, as well as the position and movements of the body, decreased by 2% per year in men and by 1.2% per year in women, for example, reveals the British journal.
If this type of change played a role in the development of cognitive impairment, the study should have found that women experienced greater loss in certain areas of the brain, such as those associated with memory. However, this is not the case. And for Fiona Kumfor, a clinical neuropsychologist at the University of Sydney, who was not involved in the study, this is not really a surprise as this type of condition is complex. She insists:
“Just looking at changes in brain size due to age is not enough to understand its full complexity.”
This study therefore does not explain the age-related difference in brain volume between men and women or understand the occurrence of Alzheimer’s disease. On the other hand, it allows, on the one hand, to have a more complete idea of the evolution of “healthy” brains over the years and, on the other hand, to rule out useless avenues for explaining cognitive disorders, and thus to guide future research on the subject.
