Association between high-sensitivity cardiac troponin I and cardiac events in elderly women

BACKGROUND: Elderly women are at high risk of coronary heart disease (CHD) and heart failure. High-sensitivity assays allow detection of cardiac troponin I (hsTnI) well below diagnostic cutoffs for acute coronary syndrome. We investigated the association between these levels with future cardiac events in community-based ambulant white women aged over 70 years initially recruited for a 5-year randomized, controlled trial of calcium supplements.

METHODS AND RESULTS: This was a prospective study of 1081 elderly women without clinical CHD at baseline (1998) or hsTnI above the diagnostic cutoffs for acute coronary syndrome with 14.5-year follow-up hospitalization and mortality (events). Two hundred forty-three (22%) women had CHD events, 163 (15%) myocardial infarction or CHD death (hard CHD), and 109 (10%) heart failure. In 99.6% of available serum samples, hsTnI was above the level of detection (median, 4.5 ng/L; interquartile range, 3.6-5.8). After adjusting for Framingham risk factors, each SD natural log-transformed hsTnI increase was associated with an increased hazard for CHD (hazard ratio, 1.34; 95% CI, 1.18-1.53; P<0.001) hard CHD (hazard ratio, 1.51; 95% CI, 1.29-1.76; P<0.001), and heart failure (hazard ratio, 1.65; 95% CI, 1.36-1.99; P<0.001). Step-wise increases in relative hazards were observed with increasing quartiles of hsTnI (P for trend, <0.001), whereas the addition of hsTnI to conventional risk factors modestly improved discrimination indices: Harrell's c-statistic, net reclassification, and integrated discrimination (P<0.05).

CONCLUSIONS: Cardiac troponin I is independently associated with future cardiac events in elderly women without apparent clinical manifestations. The addition of cardiac troponin I to conventional risk factors may modestly improve risk prediction in this setting.