Risk factors for coronary heart disease and survival after myocardial infarction

Abstract

Objectives: Several risk factors for coronary heart disease (CHD) have been associated with improved in-hospital survival after myocardial infarction (MI). We aimed to confirm this paradox and assess whether it extends to long-term outcome. In addition, we investigated temporal mortality trends.

Methods: We examined the relation between the presence of four modifiable risk factors for CHD (hypertension, dyslipidaemia, diabetes mellitus and smoking) and mortality in 14,434 consecutive patients admitted with MI to a coronary care unit from 1985 to 2008.

Results: Two-thirds of MI patients (n = 10,003) had at least one risk factor for CHD on hospital admission. The presence of at least one compared to no CHD risk factors was associated with a favourable 30-day mortality rate (5% vs. 7%, adjusted odds ratio 0.72, 95% confidence interval (CI): 0.62-0.83). There was significant interaction between the presence of CHD risk factors and decade of hospitalization (p = 0.001). The adjusted 10-year mortality hazard ratio (HR) of at least one CHD risk factor compared to none, was 1.2 (95% CI: 1.0--1.4), 0.89 (0.65--1.2) and 0.89 (0.79--0.99) in 1985--1990, 1990--2000 and 2000--2008, respectively. Survival improved over time. Adjusted 10-year mortality fell (adjusted HR [2000--2008 vs. 1985--1990] 0.59 [95% CI: 0.52--0.66] in patients with, and 0.76 [95% CI: 0.65-0.89] in those without CHD risk factors).

Conclusions: The presence of at least one modifiable CHD risk factor was associated with improved outcome after MI. Patients with CHD risk factors benefited from more substantial mortality reductions during the past few decades.

Keywords: Mortality; NSTEMI; STEMI; coronary heart disease; diabetes; hyperlipidaemia; hypertension; long-term survival; paradox; smoking.