Alzheimer's disease, APOE4 and gender: the fact is obvious, the reasons are unclear
Why do women suffer from Alzheimer's syndrome more often than men?
Kirill Stasevich, Compulenta
Among the many reasons that can cause Alzheimer's disease, there are also genetic ones. Back in 1993, scientists found out that one of the variants of the apolipoprotein E gene (APOE4) increases the likelihood of illness in old age. There are other versions of this gene: so, APOE3 does not affect the development of alzheimer's in any way, and APOE2 even reduces the likelihood of developing the disease. However, APOE2 is much less common.
But with APOE4 everything is not so simple. In 1997, a comparative analysis of several dozen papers on Alzheimer's disease was conducted, as a result of which scientists found that this gene is dangerous exclusively for women, in whom it increases the likelihood of the disease four times. For men, APOE4 turned out to be almost harmless.
Since then, the genetic-alzheimer's bias between men and women has not been studied in detail, and a 1997 meta-analysis was the only confirmation of the phenomenon. However, in 2008, these data caught the eye of Michael Greicius from Stanford (USA), who undertook directly, in a separate study, to check whether women, so to speak, are genetically more susceptible to Alzheimer's disease compared to men. By the way, some preliminary data obtained by Mr. Greicius and his group also spoke in favor of this: scientists were able to see that even without signs of the disease, women with the APOE4 gene have weaker neural connections in the brain than men with the same gene. The same thing was observed in experiments with rodents: females with APOE4, roughly speaking, were less intelligent with age than males of the same age with the same APOE4.
In the new study, researchers analyzed data on 2,588 patients with mild cognitive impairment and compared them with 5,496 healthy elderly people. Then they tracked who from both groups developed full-fledged Alzheimer's disease, and compared this with the sex of the patients and the presence of one or more copies of APOE4 in their genome.
As the researchers write in the Annals of Neurology (Altmann et al., Sex modifies the APOE-related risk of developing Alzheimer's disease), if a person had a bad variant of the gene in the genome, then cognitive impairment in him quickly developed into a full-fledged disease, regardless of what gender he was. When the comparison was carried out separately among women and separately among men, it turned out that ladies with APOE4 were twice as likely to suffer from mild cognitive impairment and alzheimer's than women with other variants of this gene.
Among men, APOE4 only slightly increased the risk of developing age-related cognitive disorders and Alzheimer's syndrome.
The authors of the work analyzed a large amount of data, in addition, people in this case were observed for quite a long time, so the results obtained can be considered a much more reliable confirmation of the female-male bias in Alzheimer's disease than the 1997 meta-analysis. This, of course, must somehow be taken into account when diagnosing the disease and predicting the condition of a person at risk.
However, in order to finally understand the reason for such a different effect of the APOE4 gene on the disease in men and women, it will be necessary to find out more precisely the molecular-cellular mechanism itself that links this gene with neurodegenerative processes in the brain.
Prepared based on the materials of the Stanford University Medical School:
Gene variant puts women at higher risk of Alzheimer’s than it does men, study finds.
Portal "Eternal youth" http://vechnayamolodost.ru16.04.2014