Heart rate variability is independently associated with C-reactive protein but not with Serum amyloid A. The Cardiovascular Risk in Young Finns Study

Background Increased levels of C-reactive protein (CRP) and serum amyloid A (SAA) are associated with an increased risk of cardiovascular disease. It is hypothesized that dysregulation of the autonomic nervous system (ANS) leads to increased inflammation via the cholinergic anti-inflammatory pathway. Heart rate variability (HRV) is a marker of ANS function. HRV has been shown to be associated with CRP levels. Currently, there are no studies addressing the relationship between HRV and SAA. Design The purpose of this study was to compare the associations between HRV, CRP and SAA in healthy young adults. CRP and SAA concentrations and short-term HRV indices [high frequency (HF), low frequency (LF), total spectral component of HRV, root mean square differences of successive R-R intervals, the standard deviation of all R-R intervals and ratio between LF and HF) were measured in 1601 men and women aged 24-39 taking part in the Cardiovascular Risk in Young Finns study. Results A significant inverse correlation (P < 0.05) between HRV indices and inflammatory markers was observed. However, in linear regression analyses, only inverse association between HRV indices and CRP levels remained significant (P < 0.05), while association between HRV indices and SAA levels was attenuated to the null (P > 0.05) after adjusting for age, sex, body mass index, cholesterol levels, leptin and other common traditional cardiovascular risk factors. Conclusions Reduced HRV indices are independently associated with increased CRP levels, but not with SAA levels. This association supports the hypothesis that dysregulation of the ANS may lead to increased inflammation early in adulthood.