Men’s health research has been grappling for years with why males consistently die younger than females and suffer higher rates of cardiovascular disease, cancer, and neurodegeneration. A growing body of genetic research now points to one factor that may cut across all of those conditions.
As men age, a significant share of their cells gradually shed the Y chromosome. According to the report, roughly 40% of men in their 60s show some degree of this loss. By age 90, that figure rises to 57%. The process is not uniform — it produces a mixed population of cells, some carrying the chromosome and some without it, a state called mosaicism. Once a cell loses the Y, every subsequent copy it generates will also lack it.
That cellular mix may be doing serious damage.
Studies have connected Y chromosome loss to cardiovascular disease, kidney disease, Alzheimer’s disease, multiple cancers, and worse survival outcomes in affected patients. Large population studies cited in the research found that men over 60 with higher levels of Y-deficient cells face a greater risk of heart attacks. Y chromosome loss also appears more frequently in individuals with Alzheimer’s, and men with elevated loss showed worse outcomes from COVID-19 — a finding that may partly explain the higher male mortality rate observed during that disease.
Why the Y Chromosome Was Underestimated
For decades, scientists considered Y chromosome loss a curiosity rather than a threat. The chromosome carries only 51 protein-coding genes (excluding duplicate copies), compared to thousands on other chromosomes. Laboratory conditions confirmed that cells can survive without it entirely. Some marsupial species lose the Y early in development, and across roughly 150 million years of mammalian evolution the chromosome has been steadily shrinking — in certain rodents, it has disappeared and been replaced altogether. That evolutionary track record made its late-life loss in humans seem unremarkable.
That assumption no longer holds.
Direct Cause or Byproduct of Aging?
Researchers acknowledge the difficulty in establishing whether Y chromosome loss drives disease or simply accompanies it. Illness and tissue repair both trigger accelerated cell division, which increases the probability of the chromosome being excluded and discarded during that process — the Y is particularly vulnerable at that stage, able to be accidentally left behind in a membrane-bound structure that the cell later removes.
Experimental evidence, though, leans toward a direct effect. In one study, mice that received Y-deficient blood cells subsequently developed measurable health problems, suggesting the loss itself contributes to harm rather than merely reflecting it. Genetic inheritance also plays a role: the research indicates approximately one-third of the variation in Y chromosome loss is heritable, involving around 150 genes linked to cell cycle control and cancer risk. Environmental factors — smoking and exposure to carcinogens — further increase the likelihood of the loss occurring.
Cells lacking the Y chromosome also appear to divide faster than normal cells, the research states, potentially giving them a competitive advantage in tissues and within tumors. That growth dynamic may explain why Y-deficient cells accumulate over time and why their concentration correlates with more serious disease outcomes.
Researchers are now working to determine whether interventions targeting Y chromosome loss could reduce its associated health risks.
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