Bradycardia has been associated with lower cardiovascular disease (CVD) risk in selected populations. There is a paucity of information available about heart rate (HR) less than 50 beats per minute (bpm) among middle-aged or older adults.
To determine whether asymptomatic bradycardia was associated with a lower cardiovascular risk profile, less subclinical atherosclerosis, and decreased incident CVD and mortality.
Design, Setting, and Participants
This retrospective analysis includes 6733 participants of the Multi-Ethnic Study of Atherosclerosis, which recruited men and women free of clinical cardiovascular disease ages 45 to 84 years from 2000 to 2002 and followed them over 10 years for incident CVD events and mortality. The HR was measured by baseline electrocardiogram. The analysis was performed in June 2014.
Main Outcomes and Measures
The association between HR categories with CVD events and all-cause mortality were examined using Cox proportional hazards models adjusted for potential confounders and mediators.
The 6733 participants had a mean (SD) age of 62 (10.2) years; 47% were male. The mean (SD) HR was 63 (9.5) bpm among the 5831 participants not taking an HR-modifying drug; 5.3% had an HR lower than 50 bpm. Preliminary results revealed significant interaction for HR categories according to use of HR-modifying drugs for mortality (P = .002); thus, all further analyses were stratified. An HR of less than 50 bpm was not associated with incident CVD in either subgroup (participants taking or not taking HR-modifying drugs). Among participants not taking HR-modifying drugs, the fully adjusted mortality risk was not different for an HR less than 50 bpm (hazard ratio, 0.71 [95% CI, 0.41-1.09]; P = .12) and increased among those with an HR greater than 80 bpm (hazard ratio, 1.49 [95% CI, 1.08-2.05]; P = .01) (reference HR, 60-69 bpm). Among the 902 participants taking HR-modifying drugs there was an elevated mortality risk associated with an HR less than 50 bpm (hazard ratio, 2.42 [95% CI, 1.39-4.20]; P = .002) and with an HR greater than 80 bpm (hazard ratio, 3.55 [95% CI, 1.65-7.65]; P = .001) (reference HR, 60-69 bpm).
Conclusions and Relevance
In a contemporary, community-based cohort, bradycardia was generally not associated with incident CVD or mortality except for a potential adverse association between bradycardia among those taking HR-modifying drugs.