The most common mutation in humans, and most men don't know they have it
For generations, the shorter lives of men have been attributed to behavior — the cigarettes, the risks, the habits. A study published in Science now points to something quieter and more fundamental: a genetic mutation in the Y chromosome that causes blood cells to gradually shed their chromosomal identity with age, accelerating the body's decline in ways that may account for more than three-quarters of the longevity gap between men and women after sixty. It is a reminder that the human story is written not only in choices, but in the slow, invisible language of biology.
- A mutation called mLOY causes men's blood cells to lose the Y chromosome with age, and it is now confirmed — not merely suspected — to accelerate disease and death.
- The scale is unsettling: one in five men over 60 carries this mutation, rising to nearly half by age 70, with those affected losing up to five and a half years of life and facing triple the Alzheimer's risk.
- Swedish researchers traced the mechanism to rogue immune cells that scar heart tissue, linking Y chromosome loss to a 30% higher risk of dying from cardiovascular disease.
- Animal trials offered a rare note of hope — mice engineered to replicate the mutation responded to an already-approved drug, pirfenidone, reversing the cardiac damage.
- Smoking dramatically accelerates the mutation's progression, but quitting allows healthier cells to recover ground, giving men one concrete lever to pull while deeper treatments are sought.
Men have long been known to smoke more, drink more, and take greater physical risks — but a new study in Science suggests the male longevity gap runs deeper than behavior. Researchers have identified a mutation called mLOY, in which blood cells gradually shed the Y chromosome as men age. A Swedish team at Uppsala University has now confirmed what scientists long suspected: this loss actively causes disease, potentially explaining more than three-quarters of the life expectancy difference between men and women after age 60.
The mutation is strikingly common. One in five men over 60 carries it; by 70, that figure rises to nearly one in two. Lead researcher Lars Forsberg calls it the most common mutation in humans. Men with significant Y chromosome loss live four to five and a half years less on average, and face three times the risk of Alzheimer's disease.
The biological pathway is now mapped. When blood cells lose the Y chromosome, immune cells called macrophages begin behaving abnormally, triggering fibrosis — scarring — in heart tissue. An analysis of nearly 16,000 cardiovascular patients confirmed a 30% higher risk of dying from heart disease among affected men. In animal studies, mice engineered without the Y chromosome developed fibrosis and died earlier; when given pirfenidone, a drug already approved for human use, the damage reversed.
Of the three known drivers of Y chromosome loss — age, inherited genetics, and smoking — only the last is controllable. Researchers found that quitting smoking allows healthy cells to gradually recover, offering men a meaningful way to slow the mutation's advance. The broader scientific work ahead involves confirming whether fibrosis is the direct cause of heart attacks in affected men, and understanding why losing a single chromosome can so profoundly reshape the aging process.
Men smoke more, drink more, and take more physical risks than women—that much has long been obvious. But a new study published in Science suggests there's something deeper happening at the genetic level, something that may finally explain why men age faster and die younger. Researchers have identified a mutation in the Y chromosome that appears to accelerate aging itself, independent of lifestyle choices.
The mutation, known as mLOY, involves the gradual loss of the Y chromosome in blood cells as men age. For years, scientists could observe this happening but couldn't prove it actually caused disease. A Swedish research team led by Lars Forsberg at Uppsala University has now done exactly that. The findings are striking: men who lose Y chromosome material in their blood face a substantially higher risk of heart disease, immune system failure, and cognitive decline. The effect is so pronounced that it may account for more than three-quarters of the life expectancy gap between men and women after age 60.
The scope of the problem is larger than many might expect. One in five men over 60 carries this mutation. By age 70, that number doubles to four in ten. Forsberg calls it "without question the most common mutation in humans." Men with significant Y chromosome loss in their blood live on average four to five and a half years shorter than those who don't experience it. The cognitive consequences are equally sobering: men with the mutation face three times the risk of developing Alzheimer's disease.
The mechanism behind the damage has now been mapped. When the Y chromosome is lost from blood cells, immune cells called macrophages begin behaving abnormally. This triggers scarring in heart tissue—a condition called fibrosis—which weakens the organ's ability to pump blood. In a study of nearly 16,000 patients with cardiovascular disease drawn from a British biobank, researchers found that Y chromosome loss was associated with a 30 percent increase in the risk of dying from heart disease. Animal studies confirmed the pathway: mice engineered to lack the Y chromosome developed fibrosis and died earlier than normal mice. When researchers gave these mice a drug already approved for human use—pirfenidone—the damage reversed.
Three factors drive Y chromosome loss, and only one is within a person's control. Age and inherited genetic mutations are inevitable. Smoking, however, is not. Kenneth Walsh, a biochemist at the University of Virginia and coauthor of the study, explained that smoking accelerates the loss of the Y chromosome dramatically. The encouraging part: if a man quits smoking, healthy cells gradually return to dominance in the bloodstream. The damage is not permanent.
The research opens significant questions for the years ahead. Scientists want to know whether men carrying the mLOY mutation actually develop fibrosis in their hearts, and whether that fibrosis is the direct cause of heart attacks and other cardiovascular events. They also want to understand the deeper biology—why losing a single chromosome has such outsized effects on aging and disease. The answers could reshape how doctors screen for and treat age-related illness in men, and might even point toward new ways to slow aging itself.
Citas Notables
It is, without question, the most common mutation in humans.— Lars Forsberg, Uppsala University
Smoking causes you to lose the Y chromosome from your blood at an accelerated rate; if you stop smoking, healthy cells return to dominance.— Kenneth Walsh, University of Virginia
La Conversación del Hearth Otra perspectiva de la historia
So this mutation—mLOY—it's not something men are born with. It happens over time?
Exactly. It's a gradual loss of Y chromosome material in blood cells as you age. Most men don't have it in their 40s. But by 60, one in five do. By 70, it's one in two.
And the study proves it actually causes disease, not just correlates with it?
That's the breakthrough. They showed it in mice—engineered them without the Y chromosome, and the animals developed heart scarring and died early. Then they reversed the damage with a drug. That's proof of causation.
Four to five years of life lost. That's enormous. Is there any way to prevent it?
Smoking accelerates it dramatically. If you quit, your healthy cells come back. But age and inherited mutations—those you can't control. The mutation itself is inevitable for many men.
So a 65-year-old man with this mutation—what does that mean for his future?
Higher risk of heart disease, cognitive decline, earlier death. But it's not a death sentence. The research is still new. They're looking at treatments now, and understanding why this happens could open doors to slowing it.
Why does losing one chromosome matter so much?
That's what they don't fully understand yet. The Y chromosome is small, carries relatively few genes. But when it's lost, immune cells malfunction in a specific way that scars the heart. The mechanism is clear now. The deeper why—that's still being worked out.