NEW YORK - Elderly men with naturally higher levels of testosterone may be less likely to suffer a heart attack or stroke than those with lower levels of the hormone, a new study finds.
Researchers found that of 2,400 Swedish men in their 70s and 80s, those with the highest testosterone levels were less likely to have a heart attack or stroke over the next several years than men with the lowest levels.
Of 604 men in the bottom quarter for levels of the "male" hormone at the study's start, 21 per cent had a heart attack, severe chest pain or stroke over roughly five years.
That compared with roughly 16 per cent of the 606 men who started out with the highest testosterone levels.
But the findings, reported in the Journal of the American College of Cardiology, do not prove that testosterone, itself, deserves the credit.
And it's too soon to recommend testosterone replacement to try to lower older men's heart risks, according to Dr. JoAnn E. Manson, chief of preventive medicine at Brigham and Women's Hospital in Boston.
"Low testosterone may be a marker of other health conditions that put men at higher risk of cardiovascular disease," said Manson, who was not involved in the research.
It's known that any serious health condition can lower testosterone levels, as can obesity.
In this study, the researchers accounted for a number of health factors -- including the men's weight, blood pressure and any diagnoses of diabetes, heart disease or stroke at the outset.
And men in the highest-testosterone group still showed a 30 per cent lower risk of heart disease or stroke compared with the other three-quarters of the study group.
But that doesn't rule out the possibility that something other than testosterone is at work, according to Manson.
What's needed, she said, is evidence from clinical trials that actually test whether testosterone replacement in older men cuts the risk of heart disease and stroke.
Those trials are ongoing. So far, Manson noted, the results are mixed on whether testosterone replacement improves "intermediate" outcomes like cholesterol or blood sugar levels.
No one yet knows if it affects the ultimate outcomes of cardiovascular disease and lifespan.
"There are many unanswered questions," Manson said. "And I don't think this means that men should be trying to boost their testosterone with testosterone replacement therapy."
The experience with hormone replacement therapy (HRT) in women offers a cautionary tale.
Before 2002, many women used HRT in the hopes of warding off heart disease and osteoporosis. Then a large US clinical trial found that women given pills containing estrogen and progesterone actually had higher risks of blood clots, heart attack, stroke and breast cancer than women given placebo pills.
Now HRT is largely used only for treating severe hot flashes -- and then, only at the lowest dose and for the shortest time possible.
"So there are concerns about the risks (of testosterone replacement) in men," Manson said.
Among those are the potential for testosterone to contribute to blood clots, liver damage or prostate cancer.
Dr. Asa Tivesten, the senior researcher on the study, agreed that older men should not start on testosterone for the sake of their hearts.
"This is a study of endogenous (natural) hormone production," said Tivesten, of Sahlgrenska University Hospital in Goteborg, Sweden. "It does not provide information about what is happening when hormones are given as a therapy."
"What we can say," Tivesten told Reuters Health in email, "is that elderly men with high testosterone levels are relatively protected against cardiovascular events, and therefore lower testosterone is a marker for increased cardiovascular risk."
As for why higher natural testosterone levels would be good for older men's hearts, there are potential reasons. Higher testosterone, Manson noted, generally means less body fat and more lean muscle, for example.
For now, though, men (and women) should stick with the tried-and-true ways of lowering heart disease risk, Manson said. That includes maintaining a healthy weight through a healthy diet and exercise, and not smoking.
For men with mildly low testosterone, Manson said, those same steps may also help boost levels of the hormone.