Independent relationship between heart rate recovery and C-reactive protein in older adults

OBJECTIVES: To examine the independent effect of parasympathetic tone (PST), assessed here according to heart rate recovery (HRR) after exercise, on circulating levels of C-reactive protein (CRP) in 132 elderly participants. DESIGN: Cross-sectional analysis using baseline data from an ongoing trial assessing the effects of exercise on immune function. SETTING: Champaign/Urbana, Illinois, vicinity. PARTICIPANTS: Community-living older adults who had been sedentary for 6 months or longer. Major exclusion criteria were current use of medications that could interfere with immunity, severe arthritis, history of cancer or inflammatory disease, recent illness or vaccination, and smoking. MEASUREMENTS: Participants were assessed for serum CRP (using enzyme-linked immunosorbent assay), cardiorespiratory fitness (peak oxygen intake (VO2)), HRR, percentage body fat (using dual-energy x-ray absorptiometry), physical activity level (according to the Physical Activity Scale for the Elderly (PASE)), fasting plasma glucose, kidney function (creatinine level), and perceived stress. RESULTS: Mean CRP level +/- standard deviation was 3.81 +/- 2.7 mg/L, placing this group in a high-risk category. After adjusting for the effects of body fat (34.6%+/- 7.4%), aspirin use, VO2 peak (19.5 +/- 3.9 mL oxygen/kg per minute), PASE, sex (64% women), and perceived stress, HRR was the only independent predictor of CRP (beta=-0.257, P=.003, change in coefficient of determination=0.060). CONCLUSION: HRR after exercise appears to be independently associated with lower CRP in older sedentary individuals, suggesting that the parasympathetic nervous system is involved in regulating chronic inflammation in older adults. Improvements in PST, as a result of regular physical exercise, may contribute to the antiinflammatory effects of exercise, independent of physical fitness or fatness.