Regular sex may help older women by cutting blood pressure – but could kill their male partners.
Men aged 57-85 who had sex once a week or more were twice as likely to have a heart attack within five years than the sexually inactive, said US researchers.
One reason for a rise in the number of heart problems could be the increased use of viagra and similar stimulants.
But for women aged between 57-85 who enjoyed an active sex life the risk of suffering high blood pressure was lower after five years than women who went without.
In the first large-scale study to look at how sex affects heart health researchers analysed data from 2,204 people in the National Social Life, Health and Ageing Project in 2005/6.
The same people were questioned again five years later for the research published in the Journal of Health and Social Behaviour.
Participants were aged 57-85 when the first wave of data was collected in 2005-06; another round of data was collected five years later.
Sociologist Prof Hui Liu Michigan State University, said: “These findings challenge the widely held assumption that sex brings uniform health benefits to everyone.
“Strikingly, we found having sex once a week or more puts older men at a risk for experiencing cardiovascular events that is almost two times greater than older men who are sexually inactive.
“Moreover, older men who found sex with their partner extremely pleasurable or satisfying had higher risk of cardiovascular events than men who did not feel so.”
Prof Liu said the findings suggest the strain and demands from a sexual relationship may be more relevant for men as they get older, become increasingly frail and suffer more sexual problems.
“Because older men have more difficulties reaching orgasm for medical or emotional reasons than do their younger counterparts, they may exert themselves to a greater degree of exhaustion and create more stress on their cardiovascular system in order to achieve climax.”
Testosterone levels and the use of medication to improve sexual function may also play a role.
Prof Liu added: “Although scientific evidence is still rare, it is likely that such sexual medication or supplements have negative effects on older men’s cardiovascular health.”
Ultimately, while moderate amounts of sex may promote health among older men, having sex too frequently or too enjoyably may be a risk factor for cardiovascular problems.
Prof Liu said: “For women, we have good news, good sexual quality may protect older women from cardiovascular risk in later life.”
Previous studies suggest that strong, deep and close relationship is an important source of social and emotional support, which may reduce stress and promote psychological well-being and, in turn, cardiovascular health.
Prof Liu said: “This may be more relevant to women than to men because men in all relationships, regardless of quality, are more likely to receive support from their partner than are women.
“However, only women in good quality relationships may acquire such benefits from their partner.”
Prof Liu said. “Physicians should talk to older male patients about potential risks of high levels of sexual activity and perhaps screen those who frequently have sex for cardiovascular issues.”