Race and Sex Differences in the Incidence and Prognostic Significance of Silent Myocardial Infarction in the Atherosclerosis Risk in Communities (ARIC) Study

Background— Race and sex differences in silent myocardial infarction (SMI) are not well established. Methods and Results— The analysis included 9498 participants from the Atherosclerosis Risk in Communities (ARIC) study who were free of cardiovascular disease at baseline (visit 1, 1987–1989). Incident SMI was defined as ECG evidence of MI without clinically documented MI (CMI) after the baseline until ARIC visit 4 (1996–1998). Coronary heart disease and all-cause deaths were ascertained starting from ARIC visit 4 until 2010. During a median follow-up of 8.9 years, 317 participants (3.3%) developed SMI and 386 (4.1%) developed CMI. The incidence rates of both SMI and CMI were higher in men (5.08 and 7.96 per 1000-person years, respectively) than in women (2.93 and 2.25 per 1000-person years, respectively; P<0.0001 for both). Blacks had a nonsignificantly higher rate of SMI than whites (4.45 versus 3.69 per 1000-person years; P=0.217), but whites had higher rate of CMI than blacks (5.04 versus 3.24 per 1000-person years; P=0.002). SMI and CMI (compared with no MI) were associated with increased risk of coronary heart disease death (hazard ratio, 3.06 [95% confidence interval, 1.88–4.99] and 4.74 [95% confidence interval, 3.26–6.90], respectively) and all-cause mortality (hazard ratio, 1.34 [95% confidence interval, 1.09–1.65] and 1.55 [95% confidence interval, 1.30–1.85], respectively). However, SMI and CMI were associated with increased mortality among both men and women, with potentially greater increased risk among women (interaction P=0.089 and 0.051, respectively). No significant interactions by race were detected. Conclusions— SMI represents >45% of incident MIs and is associated with poor prognosis. Race and sex differences in the incidence and prognostic significance of SMI exist that may warrant considering SMI in personalized assessments of coronary heart disease risk.