Doctors are finding more evidence that smoking can contribute to erectile dysfunction (ED).  Eight thousand Australian men took part in a study that determined the men who smoked more than a pack a day were 39 times more likely to have erection problems than nonsmokers. Smokers who went through less than a pack a day were 24 times more likely to be impotent. 

An earlier survey among Chinese men showed that out of 4,764 subjects, 12 percent of men who have never smoked still experienced erectile difficulties—as opposed to 15 percent of smokers and former smokers. From its results, the study concluded that smokers were 30 percent more prone to impotency. Men who smoke more than a pack a day are 60 percent more prone. 

The nicotine in cigarettes is a vasoconstrictor, which shrinks the arteries in the penis, reducing the blood flow needed to achieve and maintain an erection. 

Only 2 percent of the male population has an erection problem serious enough to consult a doctor. In addition to smoking, other lifestyle factors of ED are obesity, heavy drinking, drug use, and a sedentary lifestyle.