So-called sudden coital death is more common when a man has sex with a mistress outside than when he had sex with his wife, researchers in Italy said. Dr. Alessandra Fisher of the University of Florence and colleagues reviewed existing research on the context in which men experience sudden death during or after sex. They found both fatal and non-fatal heart attacks were relatively rare when a man has sexual intercourse with his wife, but fatal heart attacks were more frequent when he was with a lover. The study, published in the Journal of Sexual Medicine, said the reasons for the increase of fatalities were not clear -- although guilt, the stress of secrecy, younger women who might be more physically demanding and more alcohol with a mistress might all play a role, the Daily Telegraph reported.