Socioeconomic Inequality and Major Adverse Cardiovascular Events.

Importance: Low socioeconomic status is associated with increased risk of cardiovascular disease, yet it remains unclear whether this association has changed over time. Major adverse cardiovascular events (MACE) are key contributors to cardiovascular morbidity, mortality, and health care costs and, thus, are indicators of the overall cardiovascular burden. Objective: To describe temporal trends in incident MACE by equivalized income groups in the Danish population from 1988 to 2023. Design, Setting, and Participants: This nationwide, population-based open cohort study using data from Danish national registries included all residents of Denmark aged 30 years or older who were alive in each year between January 1, 1988, and January 1, 2023, and had available income observations in the current or preceding 5 years. Individuals were followed up to December 31 of each year, to death, or to emigration. Data were analyzed from August 2025 to July 2026. Exposure: Equivalized disposable household income. Main Outcome and Measures: Incident MACE, defined as the first hospital admission for acute myocardial infarction, unstable angina, stroke, or heart failure. Age-standardized incidence rates were calculated annually, stratified by income quartile and sex. Results: A total of 5 932 672 individuals aged 30 years or older were registered in the Danish Civil Registration System from 1988 to 2023. The annual study population increased from 3.06 million in 1988 to 3.85 million in 2023. Most residents in 1988 were female (52.1%), and most in 2023 were male (51.1%); the median age increased from 50.8 years (IQR, 40.2-65.6 years) in 1988 to 55.8 years (IQR, 43.3-68.8 years) in 2023. Age-standardized incidence rates of MACE decreased across all income groups from 1988 to 2023 but remained highest in the lowest income quartile. For males, the rate decreased from 191.1 (95% CI, 186.3-196.0) per 10 000 person-years to 119.6 (95% CI, 116.0-123.2) per 10 000 person-years in the lowest income quartile, while in the highest quartile it decreased from 153.5 (95% CI, 142.9-164.0) per 10 000 person-years to 85.9 (95% CI, 81.2-90.6) per 10 000 person-years. For females, the rate decreased from 116.0 (95% CI, 113.0-118.9) per 10 000 person-years to 70.4 (95% CI, 68.1-72.6) per 10 000 person-years in in the lowest income quartile and from 89.5 (95% CI, 81.9-97.2) per 10 000 person-years to 53.1 (95% CI, 49.0-57.1) per 10 000 person-years in the highest. Conclusions and Relevance: In this cohort study of Danish residents aged 30 years or older from 1988 to 2023, the incidence of MACE declined across all socioeconomic groups. Although individuals with lower income generally experienced higher incidence rates, the overall decline occurred in all socioeconomic groups.