Background
Due to improved management, diagnosis, and care of myocardial infarction (MI), patients may now survive long enough to increasingly develop serious noncardiovascular conditions.

Objectives
This study aimed to test this hypothesis by investigating the temporal trends in noncardiovascular morbidity and mortality following MI.

Methods
We conducted a registry-based nationwide cohort study of all Danish patients with MI during 2000 to 2017. Outcomes were cardiovascular and noncardiovascular mortality, incident cancer, incident renal disease, and severe infectious disease.

Results
From 2000 to 2017, 136,293 consecutive patients were identified (63.2% men, median age 69 years). The 1-year risk of cardiovascular mortality between 2000 to 2002 and 2015 to 2017 decreased from 18.4% to 7.6%, whereas noncardiovascular mortality decreased from 5.8% to 5.0%. This corresponded to an increase in the proportion of total 1-year mortality attributed to noncardiovascular causes from 24.1% to 39.5%. Furthermore, increases in 1-year risk of incident cancer (1.9%-2.4%), incident renal disease (1.0%-1.6%), and infectious disease (5.5%-9.1%) were observed (all P trend <0.01). In analyses standardized for changes in patient characteristics, the increased risk of cancer in 2015 to 2017 compared with 2000 to 2002 was no longer significant (standardized risk ratios for cancer: 0.99 [95% CI: 0.91-1.07]; renal disease: 1.28 [95% CI: 1.15-1.41]; infectious disease: 1.28 [95% CI: 1.23-1.34]).

Conclusions
Although cardiovascular mortality following MI improved substantially during 2000 to 2017, the risk of noncardiovascular morbidity increased. Moreover, noncardiovascular causes constitute an increasing proportion of post-MI mortality. These findings suggest that further attention on noncardiovascular outcomes is warranted in guidelines and clinical practice and should be considered in the design of future clinical trials.