Trends in acute coronary syndrome hospitalisation, incidence and mortality rates in young adults: an Australian linked data study.

Background: Australian and international studies have reported an attenuation in previous declines in acute coronary syndrome (ACS) events in young adults. This study examines temporal trends in admission, mortality and incidence rates for ACS in men and women aged <55 years using multijurisdictional data for 2007-2016.

Methods: This population-based linked data study used hospital and mortality records from New South Wales, Western Australia and South Australia for 2002-2016. We identified all ACS hospitalisations and deaths, and first-ever (incident) events using a 5-year lookback period. Age-specific rates were calculated for ACS subgroups. Average annual percentage changes (95% CI) were estimated from age-adjusted Poisson regression models.

Results: There were 202 327 ACS events from 2007 to 2016, 27.6% (n=55 764) of which occurred in 20-54 years. ACS admission rates declined in all age and sex groupings, with greater declines in 55-74 years. Substantial declines in mortality rates of 6%-9%/year were seen across all sex and age groups. Reductions in total incidence were driven by declines in hospitalised ACS incidence. A decline in ST-segment elevation myocardial infarction (STEMI) incidence rates was observed, with the smallest reduction in younger women (-1.7%/year). Non-STEMI incidence rates increased by 1.9%/year (95% CI +0.8, +3.0) in women aged 20-54 years while remaining unchanged in young men.

Conclusions: While reductions in ACS incidence and mortality overall are encouraging, this study highlights increasing NSTEMI incidence and a smaller decline in STEMI incidence in young women compared with young adult men. A better understanding of sex-specific factors responsible for increasing rates is essential to continue to improve cardiovascular health.