Abstract 1105: Impact of Baseline Heart Rate and Change in Heart Rate on Mortality in Presumably Healthy Subjects: The IPC Cohort
Background: though resting heart rate (HR) is a correlate of mortality in the general population, there are only few data on the impact of change in HR over time on subsequent mortality.
Aim: to determine the impact of baseline HR and change in HR over time on mortality in a large population screened at a preventive medicine center.
Methods: 64,660 subjects with 2 visits at our center, 6 years apart on average. Median time of follow-up after visit 2 was 6 years. HR was measured on an ECG recording, after 5–7 minutes rest in the supine position and was categorised in 3 groups at visit 1: <60 bpm, 60 –75 bpm and ≥75 bpm. Change in HR was categorised in stable (−0.5 to +0.5 bpm/year), mild decrease (−0.5 to −1.5 bpm/year), large decrease (≤−1.5 bpm/year), mild increase (+0.5 to +1.5) and large increase (≥1.5 bpm/year).
Results: During follow-up, 756 subjects died (1.2%). Mortality increased with increasing baseline HR: 0.8%, 1.0% and 1.7% for HR <60, 60 –75 and >75 bpm, respectively (p<0.001). However, mortality was increased for both individuals with an annual increase of HR > 1.5 bpm/year (2.0%) and those with a decrease > −1.5 bpm/year (1.4%), compared with those with a stable HR (0.9%) (p<0.001). As regards change in HR, there was no favourable impact of decreased HR, whatever the initial level of baseline HR, although a favourable trend was noted for mild decrease in subjects with baseline HR > 75 bpm (1.2% vs 1.7%, p=0.13). Using Cox multivariate analysis, risk of death was higher in people with baseline HR >75 bpm (OR=1.51; 95%CI: 1.13–2.02) and a trend was noted for HR 60 –75 bpm (OR=1.20; 95%CI: 0.93–1.56, p=0.17); likewise, risk was higher in patients with an annual increase in HR >1.5 bpm (OR=1.56; 95%CI: 1.18 –2.08), compared with those with stable HR. Other independent predictors included age, sex, socio-economic status, abnormal ECG findings, history of hypertension, higher SBP, increase in pulse pressure over time, history of smoking. Results were similar when CV mortality alone was considered.
Conclusion: although basal HR is a predictor of mortality, decrease in HR is not associated with a reduction in subsequent mortality. These data suggest that HR is a marker rather than a causal factor of mortality.