The Yale School of Medicine is participating in a study by the National Institutes of Health to determine whether testosterone treatments for older men are effective at preventing age-related health problems.

“Testosterone is commonly being prescribed in older men despite the absence of sufficient evidence that it is effective in treating these conditions,” School of Medicine professor Thomas Gill, the principal investigator for the Yale site, said in an interview. “Before it becomes fully integrated into clinical practice, we should require evidence demonstrating its benefit.”

Researchers for the study began recruiting subjects this week at the School of Medicine and 11 other sites across the country. Gill said he hopes the study, known as the “Testosterone Trial,” will provide evidence on whether testosterone therapy can reverse age-related conditions such as cognitive impairment, fatigue, cardiovascular disease and anemia.

Gill, who is the co-director of the Yale Program on Aging, said scientists are unsure about if some health problems commonly attributed to aging are aggravated by underlying factors such as testosterone deficiency.

The study, which is being coordinated by the University of Pennsylvania School of Medicine, is primarily funded by the National Institute on Aging (NIA), a component of the NIH.

Sergei Romashkan, the chief of clinical trials for the NIA, said smaller studies had only given hints of the positive effects of testosterone therapy.

Eight hundred men with low testosterone levels over the age of 65 will be recruited to participate in the study, Romashkan said. Seventy of them will be tested at Yale, he added. The men will be randomly assigned to a treatment group that will have a testosterone gel applied to their torsos or a control group that will receive a placebo gel. Over a year, the men’s testosterone levels will be measured every month for the first three months, and then every three months afterward. The researchers will test for physical function, vitality, cognition, sexual function and cardiovascular disease at the end of the year.

Romashkan said he expected the study to take six years. Recruiting subjects, he added, is expected to take a full two-and-a-half years.

Joanne McGloin, the project coordinator at the Yale site, said her staff will distribute a brochure about the study at local flu clinics and through mass mailings. The study will also place advertisements in local newspapers and recruit geriatric health specialists to speak at fraternal organizations around New Haven to spread awareness of the study, she added.

Regardless of the outcome of the study, Gill said it should provide a clear answer to doctors about the usefulness of prescribing testosterone treatments.

“When doctors have better information, they make better decisions,” Gill said. “That will improve the quality of life for older people.”

Romashkan said the total budget for the study is nearly $30 million, with a $25 million grant awarded by the NIA. Additional funding came from the National Heart, Lung, and Blood Institute; the National Institute on Neurological Disorders and Stroke; The Eunice Kennedy Shriver National Institute of Child Health and Human Development and Solvay Pharmaceuticals, the manufacturer of the testosterone gel used in the study.