Decline in resting heart rate, its association with other variables, and its role in cardiovascular disease The Tromsø Study

Abstract

Background: Resting heart rate (RHR) is an easily measured cardiovascular parameter that is considered an independent predictor of cardiovascular disease (CVD) and mortality in the general population. However, results on the association between RHR and these outcomes are inconsistent, and studies on longitudinal trends in RHR and the role of long-term changes in RHR in CVD and mortality are scarce. <br>Objective: To investigate secular trends in RHR in the general population of Tromsø, Northern Norway over the last decades, and to explore the role of RHR and long-term changes in RHR in CVD and mortality. <br>Methods: Participants from four surveys of the Tromsø Study conducted between 1986 and 2008 were included in these analyses (n=34 751). RHR in these participants was measured with an automated Dinamap device and resultant data were linked to validated information on incident myocardial infarction, atrial fibrillation, ischemic stroke, cardiovascular death and total death. Statistical methods included mixed models analysis, fractional polynomials, and trajectory analysis. <br>Main results: Over 22 years of observation, the mean age-adjusted RHR declined from 73.4 to 64.7 beats per minute in men, and from 78.3 to 66.4 beats per minute in women; 17.4% of the decline in men and 16.1% of the decline in women was attributable to favourable changes in other cardiovascular risk factors. In men, elevated RHR independently predicted the risk of myocardial infarction, atrial fibrillation, and cardiovascular death. In women, the associations with myocardial infarction and total death were similar to those in men, and we found a J-shaped association with ischemic stroke. Having a constantly elevated RHR or a RHR that increased from moderate to high over 15 years increased the risk of myocardial infarction, cardiovascular death, and total death in men, whereas estimates in women were insignificant. <br>Conclusions: Over the last decades RHR has declined substantially, and this decline has occurred to a large extent independently of other cardiovascular risk factors. RHR independently predicts the risk of CVD and mortality though there are sex differences. Long-term changes in RHR provide additional information for risk assessment. Thus, RHR is as an independent cardiovascular risk factor, and as such it should be monitored and used in risk assessments by both people themselves and by health professionals. RHR is a modifiable cardiovascular risk factor; however it is unclear whether people could benefit from RHR-lowering interventions.