Fresh clues have been uncovered that might help explain why men typically don't live as long as women.
On average, in every human population, women’s life span is almost 8% longer than men’s life span, according to researchers. Furthermore, they claim this pattern has held since the first birth records became available in the 18th Century. With nine out of ten people who live to be 110 years old female, scientist have been looking for ways to explain the gender lifespan gap.
A new study has suggested the loss of the male sex Y chromosome could be at play.
‘Disheartening Loss’
Chromosomes - bundles of DNA in each cell - come in pairs. Women have two X chromosomes, while men have an X and a Y chromosome.
Many men as they get older don’t just lose their hair and overall muscle tone, but also start to lose Y chromosomes from their cells.
Scientists have previously linked this to the possibility of a higher risk of death, but up until now the evidence was deemed circumstantial.
For the study, Hematopoietic loss of Y chromosome leads to cardiac fibrosis and heart failure mortality research, Professor Kenneth Walsh, from the University of Virginia (UAV) and his colleagues performed bone marrow transplants on 38 mice.
After that, they used the CRISPR-Cas9 gene-editing tool to remove the Y chromosome number from 49% to 81% of white blood cells. This is estimated to be the same percentage as in many humans with Y-chromosome loss.
For nearly 2 years, the researchers followed both groups of animals, discovering that Y-lacking rodents were more likely to die during this period. Losing the chromosome had spurred on the onset of fibrosis, or scarring, in the heart, resulting in heart failure and an earlier death, the team concluded.
As they published their findings in Science journal, the team underscored the importance of this new evidence that shedding the Y chromosome “leads to a staggering amount of years of life lost” most likely because hearts became stiffer.
By analyzing blood samples - the easiest way to detect loss of Y - researchers have found the chromosome is missing from some white blood cells in about 40% of 70-year-olds and 57% of 93-year-olds. In some older men, more than 80% of the cells can be Y chromosome-deficient.
"Particularly past age 60, men die more rapidly than women. It's as if they biologically age more quickly. This new research provides clues as to why men have shorter lifespans than women," the author of the study, Professor Kenneth Walsh said.
To tackle this problem, men could benefit from an existing drug that targets dangerous tissue scarring. Pirfenidone may help counteract the harmful effects of the chromosome loss, Walsh said.