Night-time heart rate nondipping: clinical and prognostic significance in the general population

Aim: Studies addressing the association between a reduced drop of heart rate (HR) at night with subclinical organ damage and cardiovascular events in the general population are scanty. We evaluated this issue in individuals enrolled in the Pressioni Monitorate E Loro Associazioni study. Methods: At entry, 2021 individuals underwent diagnostic tests including laboratory investigations, 24-h ambulatory blood pressure (BP) monitoring and echocardiography. Participants were followed from the initial medical visit for a time interval of 148 ± 27 months. To explore the association of circadian HR rhythm and outcomes, participants were classified in the primary analysis according to quartiles of nocturnal HR decrease. In secondary analyses, the population was also classified according nondipping nocturnal HR (defined as a drop in average HR at night lower than 10% compared with day-time values) and next in four categories: first, BP/HR dipper, second, BP/HR nondipper, third, HR dipper/BP nondipper, fourth, HR nondipper/BP dipper). Results: A flattened circadian HR rhythm (i.e. lowest quartile of night-time HR dip) was independently associated with left atrial enlargement, but not to left ventricular hypertrophy; moreover, it was predictive of fatal and nonfatal cardiovascular events, independently of several confounders (hazard ratio 1.8, confidence interval: 1.13-2.86, P < 0.01 vs. highest quartile). Conclusion: A blunted dipping of nocturnal HR is associated with preclinical cardiac damage in terms of left atrial enlargement and is predictive cardiovascular morbidity and mortality in the general population