Editor's Note: Commentary based on Ó Hartaigh B, Lovato LC, Pahor M, et al. Effect of a long-term physical activity intervention on resting pulse rate in older persons: results from the lifestyle interventions and independence for elders study. J Am Geriatr Soc 2016;64:2511-6.

Rationale for Study/Background: The resting pulse rate (RPR) is an indicator of physical fitness with a higher RPR strongly associated with increasing number of cardiovascular events. A small study of 424 individuals demonstrated no benefit of moderate-intensity aerobic training to lower RPR.¹ Larger studies of longer duration were felt to be needed to address the effect of moderate-intensity aerobic training on lowering RPR.

Funding: Funding for the LIFE (Lifestyle Interventions and Independence for Elders) trial was provided by the National Institute of Aging (NIA) Claude D. Pepper Older Americans Independence Center.

Methods: The LIFE trial was a multicenter, randomized clinical trial comparing physical activity (PA) intervention with successful aging (SA) intervention for the primary outcome of performance of a 400-meter walk test.^2,3 Several secondary (cognitive function, serious fall injury, disability questionnaire, cost-effectiveness analysis), and tertiary (incident dementia, short physical performance battery, sleep-wake disturbances, ventilatory capacity and dyspnea, respiratory questionnaire, Borg index, cardiovascular and pulmonary events) outcomes were also assessed. The findings from the primary study demonstrated that PA intervention reduced major disability over 2.6 years among older adults.

PA consisted of a combination of walking, strength, balance and flexibility exercises (two supervised center based exercise sessions/week and up to four home-based PA sessions/week). SA intervention consisted of small-group weekly sessions for the first 26 weeks and monthly thereafter. The goal of SA intervention was to increase awareness of health related topics (negotiate health system, medications, foot care, preventive services, nutrition, etc.). Each session ended with a short instructor led program (5-10 minutes) of upper extremity stretching exercise.

The current study is a post hoc analysis comparing PA and SA for the primary outcome of RPR (measured by palpation of the radial artery for 30 seconds, multiplied by two, with the mean of two measurements used). Measurements were obtained at baseline, 6, 18, and 30 months. A comparison was also done of RPR with palpation and RPR obtained by electrocardiogram.

Statistical Analysis: A repeated measures regression using a mixed effects model and an unstructured covariance matrix. Models were adjusted for clinic site, sex and baseline value of the RPR.

Results: Total of 1,635 patients. PA group (N = 818), SA group (N = 817); mean age 78.9± 5.2, 67% female, 76% white. Baseline characteristics were similar for both groups. The frequency of engaging in walking related activities were higher in the PA group (median 16 times/week) compared to the SA group (median 12 times/week).

The average effect of PA intervention was statistically significant but clinically quite small (a decrease of 0.84 beats/minute, 95% CI: 0.17-1.51; P_average=0.01) with the most pronounced effect occurring at 18-months (1.37 beats/minute, 95% CI: 0.48-2.26 beats/minutes). At 30 months the association was weaker and not statistically significant. These findings were similar to those obtained by using the electrocardiogram for RPR. Further subgroup analysis did not show substantial differences between the two groups.

Conclusion: Moderate intensity physical activity over an average of 2.6 years in a cohort of community-dwelling older adults resulted in a statistically significant but clinically very small reduction of resting pulse rate.

Limitations of Study/Perspective: The current study did not examine more vigorous exercise, which has been shown to confer a more meaningful decrease in RPR over short-term follow-up. The authors also point to the possibility of self-referral bias in recruitment and acknowledge that the findings may not be generalizable to the broader community of older adults.

While resting heart rate is generally considered a surrogate for cardiovascular fitness, it is influenced by many factors, including smoking, alcohol, caffeine, hydration state, sinus node function (especially in older adults), autonomic tone, and numerous medications, all of which are subject to change over time. In the present study, the PA intervention was associated with a very modest reduction in RPR relative to the SA intervention. However, the clinical significance of this change, if any, is difficult to assess in the absence of longitudinal data on several key potentially confounding variables. More importantly, RPR is unlikely to be a valid surrogate for evaluating the cardiovascular benefits of regular PA in older adults, which include muscle conditioning, improved physical and mental function, favorable effects on multiple cardiovascular risk factors, and compression of disability and dependency. Hence, although additional study is needed, the findings of the present analysis should not be interpreted as a strike against the major health benefits accruing to older adults who participate in regular PA.

References

1. O'Hartaigh B, Pahor M, Buford TW, et al. Physical activity and resting pulse rate in older adults: findings from a randomized controlled trial. Am Heart J 2014;168:597-604.
2. Fielding RA, Rejeski WJ, Blair S, et al. The Lifestyle Interventions and Independence for Elders Study: design and methods. J Gerontol A Biol Sci Med Sci 2011;66:1226-37.
3. Marsh AP, Lovato LC, Glynn NW, et al. Lifestyle interventions and independence for elders study: recruitment and baseline characteristics. J Gerontol A Biol Sci Med Sci 2013;68:1549-58.

Keywords: Adult, Aged, Cardiovascular Diseases, Confounding Factors, Epidemiologic, Dementia, Electrocardiography, Heart Rate, Life Style, Radial Artery, Risk Factors, Sinoatrial Node

< Back to Listings