Relation of heart rate recovery after exercise to C-reactive protein and white blood cell count

Abstract

This study was conducted to test the hypothesis that slow and abnormal heart rate recovery (HRR), an indicator of decreased autonomic nervous system activity, after exercise is associated with inflammatory markers. Subjects who underwent exercise treadmill testing (n = 5,527, mean age 50.4 +/- 8.5 years) were studied in a cross-sectional design. HRR was calculated as the difference between maximum heart rate during the test and heart rate 1 minute after the cessation of exercise. Abnormal HRR was defined as < or =12 beats/min. Subjects with abnormal HRR had higher levels of log C-reactive protein (CRP; 1.38 +/- 0.6 vs 1.11 +/- 0.4 mg/dl, p <0.001) and higher white blood cell counts (6.9 +/- 2.1 vs 6.2 +/- 1.7 x 10(9) cells/L, p <0.001) than those with normal HRR. HRR was associated with CRP (r = -0.21, p <0.001) and white blood cell count (r = -0.19, p <0.001). HRR was independently associated with CRP (beta = -0.13, p = 0.001) in a stepwise multiple regression. In a logistic multivariate model, the group within the highest quartile of CRP (odds ratio 1.54, 95% confidence interval 1.05 to 2.27) was more likely to have abnormal HRR than those within the lowest quartile. In conclusion, slow and abnormal HRR after exercise testing is associated with inflammatory markers, which could contribute to the high incidence of cardiovascular disease in these subjects.