Abstract 6210: The Relation between High Cardiorespiratory Fitness and Low Inflammation is Mediated by Autonomic Nervous System Function

Abstract

Objective: Although observational studies have shown an inverse association between high cardiorespiratory fitness (CRF) and low inflammatory markers independent of body fatness, the underlying mechanisms relating CRF to inflammatory markers are not fully understood. There is emerging evidence that autonomic nervous system function is related to inflammation. Because high CRF is related to improved autonomic function, we hypothesized that association between high CRF and low inflammatory markers would be affected by autonomic nervous system function. Methods: Cross-sectional analyses were conducted on 2557 (mean age 57 ± 5 yrs) asymptomatic men who participated in a medical checkup program. Fasting blood samples for CVD risk factors including inflammatory markers were analyzed and CRF was measured by maximal exercise treadmill test with expired gas analysis. We used an index of cardiac autonomic imbalance defined as the ratio of resting heart rate with 1 minute of heart rate recovery after exercise (index of RHR/HRR). Results: CRF was significantly correlated with age (r=−0.41, p<0.05), body mass index (BMI) (r=−0.11, p<0.05), glucose (r=−0.13, p<0.05), C-reactive protein (CRP) (r=−0.16, p<0.05), white blood cell (WBC) (r=−0.17, p<0.05), and index of RHR/HRR (r=−0.48, p<0.05). Index of RHR/HRR was also significantly correlated with age (r=0.36, p<0.05), glucose (r=0.23, p<0.05), CRP (r=0.25, p<0.05) and WBC (r=0.23, p<0.05). In multivariable linear regression models that adjusted for age, BMI, smoking, diseases, medications, lipid profiles, glucose and systolic blood pressure, CRF was inversely associated with CRP (β=−0.09, p<0.05). However, this relationship was no longer significant after adjusting for index of RHR/HRR in a multivariable linear regression model (β=−0.03, p=0.29). Conclusion: These results suggest that autonomic nervous system function significantly mediated the relationship between high cardiorespiratory fitness and inflammation, but further interventional research is needed to confirm this novel finding.