MEN who smoke risk ruining their sex lives - and not just because they may run out of puff or cough and kill the mood. 'Smoking can seriously shrink your manhood,' warned anti-smoking crusader Dr Judith Mackay, who said smoking caused blood vessels in the penis to narrow significantly. Smokers, she said, were twice as likely to be impotent as non-smokers. And if smokers were not made entirely impotent, then erections could take longer to achieve and their staying power be affected. Dr Mackay is director of the Asian Consultancy on Tobacco Control. Her comments were made during a speech this week to the Rotary Club of Hong Kong North. 'Coughing, shortness of breath and chest pain from tobacco use can interfere with sex performance,' she said. 'Heavier smokers even ejaculate a decreased volume of semen.' Dr Mackay said smoking affected not only sexual performance but sex appeal, with men 93 per cent more likely to go bald if they smoked and four times as likely as non-smokers to become grey-haired early. And the warning was not just for men - smoking can also lower hormone levels in women. Smoking also starved the skin of oxygen by reducing circulation, decreased the production of collagen and reduced the skin's water and vitamin C content, all of which led to wrinkles. And for couples planning parenthood, there was yet another warning. 'Teenage males who smoke cigarettes appear to risk sperm damage that can cause genetic abnormalities in their children, and may even affect the future fertility of their children,' Dr Mackay said. 'There's considerable scientific evidence that smoking decreases sperm production, degrades sperm quality, reduces sperm viability and mobility, and significantly reduces blood flow to the penis. 'Tell any infertile couple to stop smoking for three months and their chances of conceiving rockets,' Dr Mackay said.