Long-term non-cardiovascular morbidity risk remains elevated following myocardial infarction: a nationwide cohort study
Authors: Christensen D M , El-Chouli M , Strange J E , Nouhravesh N , Sindet-Pedersen C , Schjerning A , Schou M , Gislason G , Sehested T S G 
Published: October 2022

Abstract

Introduction
Risk of cardiovascular events following myocardial infarction (MI) is high, and secondary preventive treatment is largely focused on reducing future cardiovascular risk. As gradual implementation of guideline-based treatments successfully leads to improved survival, long-term non-cardiovascular morbidity is likely of rising importance following MI.

Purpose
To determine the long-term risk of non-cardiovascular morbidity in a contemporary MI population with the aim of informing the need for and scope of prolonged surveillance.

Methods
We included all patients with a first-time MI in Denmark from 2001–2018 matched on age, sex, and date of discharge with up to 4 general population controls. We used the Aalen-Johansen estimator to estimate 1-year and 5-year risk of non-cardiovascular morbidity with death as a competing risk. Non-cardiovascular morbidity was defined as an in-patient hospital admission for any primary cause excluding cardiovascular diagnoses (International classification of diseases, 10th revision codes: I00–99). We also calculated 2-year and 6-year risks of non-cardiovascular morbidity in a stable population of post-MI patients and matched controls, i.e., participants alive with no hospital admissions for 1 full year following study entry. Finally, we estimated 1-year and 5-year risks of cause-specific non-cardiovascular morbidity.

Results
A total of 124,072 patients with MI who survived to hospital discharge were matched with 496,277 general population controls. Median age was 68 years and 35.5% were female. The 1-year and 5-year risk of non-cardiovascular morbidity was elevated for patients with MI compared to controls: 38.6% (95% confidence interval: 38.3–38.9) vs 15.3% (15.2–15.4) and 64.8% (64.6–65.1) vs 45.8% (45.7–45.9), respectively (Figure 1). Regarding cause-specific morbidity, risks of respiratory disease, gastrointestinal disease, and infectious disease particularly were high (Figure 2). For example, 1-year risk of infection was 4.5% for patients with MI and 1.8% for controls and 5-year risk of respiratory disease was 16.3% for patients with MI and 9.7% for controls. Furthermore, in the stable population (patients with MI, n=50,144; controls, n=159,467, median age 64 years, 33.0% female), risk of non-cardiovascular morbidity remained elevated at 2 years (17.2% [16.8–17.5] vs 11.3% [11.1–11.5]) and 6 years (49.2% [48.7–49.7] vs 39.8% [39.6–40.1]) post MI (Figure 1).

Conclusions
Risk of non-cardiovascular morbidity was high in patients following myocardial infarction, particularly for respiratory disease, gastrointestinal disease, and infectious disease. The risk remained elevated during long-term follow up. The study highlights the importance of additional focus on non-CV morbidity to further improve outcomes.

Funding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): Danish Heart Foundation