Quantifying the effect of age on short-term and long-term case fatality in 14,000 patients with incident cases of cardiovascular disease.

BACKGROUND: Age is a major determinant of case fatality following acute cardiovascular disease (CVD) events. Its impact, however, varies by time after the event, sex and diagnostic category. We were able to quantify these effects with good precision in a large cohort of patients.

DESIGN: A national cohort of 14,227 CVD patients representing all the recorded first-CVD events in people aged 35-84 years in New Zealand in 1995 were examined, using electronic linkage of routine health data.

METHODS: Case fatality by age was assessed in three phases: prehospital deaths, fatality after hospitalization up to 28 days and from 28 days up to 5 years after the event. It was assessed in these phases by sex and by the diagnostic categories: acute myocardial infarction (AMI), stroke and other coronary heart diseases.

RESULTS: Case fatality in the prehospital phase showed substantial age differences. In particular, a strong positive monotonic age gradient was observed for AMI, but a U-shaped age-case-fatality gradient for stroke. From admission to 28 days, AMI case fatality demonstrated the strongest age gradient. In contrast, there was minimal age effect on 28-day stroke mortality, and case fatality for other coronary heart diseases was low. From 28 days to 5 years, there was a substantial positive monotonic age by case-fatality gradient for all diagnoses.

CONCLUSION: Age has a large impact on case fatality following cardiovascular events, although the effect varies significantly by time elapsed after the event, diagnostic category and sex. As the lifetime benefits of many cardiovascular interventions depend on preintervention risk and case fatality, the role of age needs careful attention while making treatment decisions.