Erectile dysfunction is the consistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance. In a study of 4,763 Chinese men aged 35 to 74 years who were free of blood vessel disease and who reported that they had been sexually active within the last 6 months, the researchers found a significant statistical link between the number of cigarettes smoked and the likelihood of erectile dysfunction.

"The association between cigarette smoking and erectile dysfunction was found in earlier studies," said first author Dr. Jiang He of Tulane University School of Public Health, New Orleans. "However, most of those studies were conducted in patients with hypertension (high blood pressure), diabetes and cardiovascular disease. What distinguishes this study is that it is the first to find this association among healthy men."

Overall, men who smoked had a 41-percent greater risk of erectile dysfunction than men who did not, the team reports in the American Journal of Epidemiology.

And there was a clear "dose-response" relationship, meaning that the more the men smoked, the higher was their risk of erectile dysfunction. Compared with non-smokers, men who smoked up to 10 cigarettes per day had a 27-percent greater likelihood of erectile dysfunction; those who smoked 11 to 20 butts a day had a 45-percent greater likelihood of erectile dysfunction; and those who smoked more than 20 cigarettes daily had a-65 percent greater chance of suffering erectile dysfunction.

The investigators estimate that 22.7 percent of erectile all dysfunction cases among healthy Chinese men ¡ª or 11.8 million cases ¡ª might be caused by cigarette smoking.