The finding comes from a study of British men aged 40 to 79 by University of Cambridge gerontologist Kay-Tee Khaw, MBBCh, and colleagues.
"The men with lower testosterone levels had an increased risk of dying from any cause, but most particularly of cardiovascular disease," Khaw tells WebMD. "We looked at cancer, too, and found no evidence of a link to cancer with higher testosterone levels."
Nearly 12,000 men enrolled in the long-term study from 1993 to 1997. More than 800 of the men died by 2003; Khaw compared these men's testosterone levels to those of some 1,500 living study participants.
After adjusting for factors that might affect risk of death -- including age, weight, smoking, alcohol use, high blood pressure, diabetes, physical activity, education, and social class -- the link between low testosterone and earlier death remained.
Compared to men with the lowest quartile (25%) of testosterone levels:
- Men in the second lowest quartile were 25% less likely to die.
- Men in the second highest quartile were 38% less likely to die.
- Men in the highest quartile were 41% less likely to die.
"We found that low testosterone predicts early mortality in men over the next 10 years or so," Khaw says. "But we think this finding needs to be replicated. We would like others to look at this in other populations of men and see if they get the same results."
The findings make sense to Robert Davis, MD, professor of urology at the University of Rochester, N.Y. Davis says low testosterone is common among men with metabolic syndrome -- a constellation of risk factors including abdominal fat, high blood sugar, high blood pressure, low HDL cholesterol, and high blood-fat levels.
"Certainly I'm not surprised at this finding. It's been shown that low testosterone correlates with metabolic syndrome, which is related to diseases like diabetes, heart disease, and vascular disease," Davis tells WebMD. "The need to check testosterone levels in people with metabolic syndrome is being recognized more and more among physicians."
Testosterone Therapy: Studies Needed
Low testosterone may be bad, but it is not clear that testosterone replacement therapy corrects this problem. Only clinical trials can prove whether testosterone supplementation can lower the risk of death linked to low testosterone levels. Ironically, researchers have been reluctant to test testosterone replacement in clinical trials because of worries that the treatment may increase men's risk of prostate cancer.
"Our study may provide some reassurance of those planning trials of testosterone supplementation," Khaw says. "The irony is that while a lot of men believe testosterone supplements may be good for their health, those trials have not been done because of ethical concerns of testosterone causing prostate cancer."
Davis worries that doctors are too wary of prescribing testosterone supplements for men with too-low testosterone levels.
"It is a very underdiagnosed and undertreated problem," he says. "One of the myths is that androgen supplementation will cause a cancer. We know that prostate cancer often regresses when androgen is removed, but there is very little evidence that supplementing to normal levels increases risk of cancer, and some evidence it may lower it."
Khaw and colleagues report their findings in the Dec. 4 issue of the journal Circulation.