Low levels of testosterone may increase the long-term risk of death in men older than 50, according to a large study being presented Tuesday, June 5, at The Endocrine Society’s 89th Annual Meeting in Toronto.

The new study is only the second report linking deficiency of this sex hormone with increased death from all causes over time, said study author Gail Laughlin, PhD.

Our average follow-up of 18 years strongly suggests that this association is not simply due to some acute illness, said Laughlin, an assistant professor of Family and Preventive Medicine at the University of California, San Diego.

In the study, Laughlin and co-workers looked at death from any cause in nearly 800 men ages 50 to 91 years who were living in a southern California community and who participated in the Rancho Bernardo Study in the 1980s. At the beginning of the study, almost one-third of these men had suboptimal blood testosterone levels for men their age. The men with low testosterone levels had a 33 percent greater risk of death during the next 18 years than the men with higher testosterone. This difference was not explained by smoking, alcohol intake and level of physical activity or by pre-existing diseases such as diabetes or heart disease.

Men with low testosterone were more likely to have elevated markers of inflammation, called inflammatory cytokines, which contribute to many diseases. Another characteristic that distinguished the men with low testosterone was a larger waist girth along with a cluster of cardiovascular and diabetes risk factors related to this type of fat accumulation. Metabolic syndrome is the name for the presence of three or more of these risk factors, which include waist measurement more than 40 inches in men (more than 35 inches in women), low HDL (good) cholesterol, high triglycerides (levels of fat in the blood), high blood pressure and high blood glucose (blood sugar).

Testosterone supplementation increasingly is being used in the United States, despite limited evidence from clinical trials as to its safety and benefits for disease prevention, according to Laughlin. While these results support proponents of supplemental hormone therapy in older men with testosterone deficiency, only randomized clinical trials can determine whether testosterone supplements are safe and can promote longevity, she said. Lifestyle modifications aimed at preventing or decreasing obesity may also increase longevity.

The National Institute on Aging and the American Heart Association funded this study.

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