Higher resting heart rate and lower heart rate variability in elderly patients were associated with poor functional status and higher risk of future functional decline, data from the PROSPER (Prospective Study of Pravastatin in the Elderly at Risk) trial indicate.
Giulia Ogliari, MD, of the Department of Gerontology and Geriatrics at Leiden University Medical Center in the Netherlands, and colleagues analyzed data from more than 5042 participants in a randomized, controlled trial that examined the effect of paravastatin in a large group of men and women, aged 70 to 82 years. They aimed to determine whether heart rate and heart rate variability were associated with a decline in functional status of high risk older adults, independent of potential cardiovascular risk factors or comorbidities.
Study participants were excluded from the final analysis as follows: 150 participants with missing baseline heart rate measurements, 489 participants with cardiac rhythm “not generated by sinoatrial node,” and 123 participants with missing data relating to functional status.
The researchers performed 10-second, 12-lead electrocardiographs (ECGs) to determine baseline resting heart rate. The standard deviation of normal-to-normal RR intervals (SDNN) was used to calculate baseline heart rate variability. Researchers assessed functional status using both the Barthel Index to measure basic activities of daily living (ADL) and the Lawton Instrumental Activities of Daily Living Scale (IADL). ADL and IADL scores ranged from 0 to 20 and 0 to 14, respectively; higher scores indicate higher independence and better functional status. After baseline measurements, ADL and IADL scores were reassessed at 9, 18, 30, and either 36 or 42 months.
At baseline, median resting heart rate was 65 beats per minute and SDNN was 18.6 ms, respectively.
Participants with higher resting heart rates tended to be older female current smokers with a high BMI and high prevalence of diabetes. In contrast, participants that skewed toward a lower resting heart rate exhibited a higher prevalence of myocardial infarction (all P values < .05).
Participants with a higher resting heart rate and lower SDNN performed worse on both ADL and IADL functional status tests (P for trend < 0.05 for all). After full adjustments to account for cardiovascular risk factors, cardiovascular morbidities, use of medications, and statin treatment group, researchers found the same association between SDNN and both ADL and IADL (P for trend = .03 and .11, respectively).
Overall, the PROSPER study data revealed that both higher resting heart rate and lower heart rate variability were associated with poor functional performance at baseline and a high risk of functional decline in the future. Those with a resting hear rate in the 71–117 beats/min range had a 1.79-fold (95% CI: 1.45–2.22) and 1.35-fold (95% CI:1.12–1.63) higher risk of decline in ADL and IADL, respectively (P for trend < .001 and .001, respectively). Those with an SDNN ranging from 1.70–13.30 ms had 1.21-fold (95% CI: 1.00–1.46) and a 1.25-fold (95% CI:1.05–1.48) higher risk for decline in ADL and IADL, respectively (both P for trends < .05)
“Further research is needed to establish whether heart rate and heart rate variability are risk markers and/or potentially modifiable risk factors for functional decline,” the authors wrote.