New research suggests that people ages 30 to 69 who live alone are almost twice as likely as those who live with a partner to suffer angina, heart attacks or sudden cardiac death.

Danish researchers studied more than 138,000 subjects in Aarhus, Denmark's second largest city, over a two-year period ending in March 2002. The report appears in the August issue of The Journal of Epidemiology and Community Health.

The best predictors of acute cardiac syndrome were age and living alone. Dr. Kirsten Melgaard Nielsen, the lead author of the study and an internist at Aarhus Sygehus University Hospital, said that it was not living alone itself that increased the risk, but the health practices of those who lived without partners. ''They're less likely to exercise, they eat more fat, and they're more likely to smoke and have high cholesterol,'' she said.

For women over 60 and men over 50, the risk was even greater. Researchers concluded that they were almost three times as likely to suffer heart problems if they had no partner.

The scientists found that sudden cardiac death was even more strongly associated with single living than angina or heart attack, a fact they attribute to a lone person's decreased ability to call for emergency help.

''Doctors should look carefully at social markers in evaluating a patient's risk for heart disease,'' Dr. Nielsen said. ''If they do, they are more likely to find risk factors that they can treat.''