Fatherhood may be a kick in the old testosterone, but it may also help keep a man alive. New research suggests that dads are a little less likely to die of heart-related problems than childless men are.
The study -- by the AARP, the government and several universities -- is the largest ever on male fertility and mortality, involving nearly 138,000 men. Although a study like this can't prove that fatherhood and mortality are related, there are plenty of reasons to think they might be, several heart disease experts said.
Marriage, having lots of friends or even having a dog can lower the chance of heart problems and cardiac-related deaths, previous research suggests. Similarly, kids might help take care of you or give you a reason to take better care of yourself.
Also, it takes reasonably good genes to father a child. An inability to do so might mean a genetic weakness that can spell heart trouble down the road.
"There is emerging evidence that male infertility is a window into a man's later health," said Dr. Michael Eisenberg, a Stanford University urologist and fertility specialist who led the study. "Maybe it's telling us that something else is involved in their inability to have kids."
The study was published online Monday by the journal Human Reproduction.
Last week, a study by other researchers of 600 men in the Philippines found that testosterone, the main male hormone, drops after a man becomes a dad. Men who started with higher levels of it were more likely to become fathers, suggesting that low levels might reflect an underlying health issue that prevents reproduction, Eisenberg said.
In general, higher levels of testosterone are better, but too much or too little can cause HDL, or "good cholesterol," to fall -- a key heart disease risk factor, said Dr. Robert Eckel, past president of the American Heart Association and professor of medicine at the University of Colorado, Denver.