Men, that ticking you hear might be your biological clock.
As women age, fertility wanes, and the risk of genetic problems in their babies increases. Now, a growing body of research suggests that middle-aged men might be more likely to father children with mental health problems, as well as rare genetic disorders, such as the most common type of dwarfism. The findings are mixed.
For example, a recent study of Swedes born between 1973 and 2001 found that those born to fathers 45 and older were more likely to have a variety of brain and nervous system conditions — such as autism, bipolar disorder, schizophrenia, and ADHD — because of an increase in mutations in older men’s sperm. Also, children of older fathers were more likely to get bad grades in school, do drugs, and attempt suicide.
‘Men Have Reproductive Aging’
U.S. sperm banks discourage donors who are 40 and older. Research suggests that sperm quality declines with age, although British scientists recently reported that the woman’s age appeared to be more of a factor than the sperm donor’s in achieving a pregnancy.
In the medical community, it isn’t always appreciated that men have reproductive aging as well.Some of the research about age-related decreases in the quality of sperm is controversial, but if you look collectively at the data that’s been published, there seems to be some decline in total sperm count and some decrease in volume. That’s not totally surprising, since testosterone levels gradually fall once men are past young adulthood. But even though semen quality goes down a bit, the men largely are still fertile
In fact, the percentage of U.S. men fathering children in their 40s or early 50s has been growing, according to the National Center for Health Statistics. For men 40-44, the birth rate — the number of men out of 1,000 who fathered a child — has crept up every year since 1980. In 2012, the birth rate for that age group was 26.8, compared to 17.1 in 1980. For men 45-49, the 2012 birth rate was 8.6, up from 6.1 in 1980. And for men 50-54, the 2012 birth rate was 2.6, up from 2.1 in 1980. In case you’re wondering, the birth rate for men 55 and older has held pretty stable for more than 30 years at 0.3.
While women are born with all the eggs they’ll ever have, sperm are constantly turning over. That constant turnover increases the likelihood of spontaneous mutations. So while middle-aged men might not have much trouble fathering children, the extra mutations in their vintage sperm might help explain an increased risk of brain and nervous system problems and rare genetic conditions in their offspring.
One of the most attention-getting studies on this subject involved 78 Icelandic trios consisting of mother, father, and child. In a paper published in 2012 in Nature, the researchers reported that, on average, men had two mutations in their sperm each year. The scientists estimated that the number of new mutations in sperm doubled every 16 ½ years, leading them to conclude that the father’s age at conception, not the mother’s, was the main reason for new hereditary mutations in their children. Their findings raise the question of whether the reported increase in autism spectrum disorder diagnoses might at least partially stem from a rise in the average age of fathers at conception, the scientists concluded.
Source: webmed
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