Men taking testosterone treatment could be at a higher risk of heart diseases and stroke, a new study reported.

About 2.9 percent of all men in the U.S. over 40 years are now taking supplements to cope with symptoms of low testosterone, or "low T.' According to the study authors, annual prescriptions for testosterone increased five-fold between 2005 and 2011. Currently, the market for these supplements is about $1.6 billion annually.

The latest study was conducted by researchers at University of Texas at Southwestern Medical Center, Dallas and their colleagues. They found that men who used testosterone were 30 percent more likely to suffer from a heart disease or stroke when compared with men who didn't use these therapies. The study was based on data from 8,709 men who underwent coronary angiography in the Veterans Affairs (VA) system between 2005 and 2011. All men in the study were suffering from low testosterone levels.

The research doesn't imply that testosterone therapy causes heart disease. However, it provides substantial evidence to support the link between the hormone use and future health complications. Previous research has found that topical testosterone raises risk of cardiovascular events and stroke in older men.

"These findings raise concerns about the potential safety of testosterone therapy," the authors wrote in the study. "Future studies including randomized controlled trials are needed to properly characterize the potential risks of testosterone therapy in men with comorbidities.

The study is published in the Journal of the American Medical Association (JAMA).