Accepted for/Published in: JMIR mHealth and uHealth
Date Submitted: Feb 19, 2019
Date Accepted: Aug 19, 2019
Heart rate variability measured with a wrist-worn sensor is related to older adults’ physical function
ABSTRACT
Background:
Heart rate variability (HRV), or variation in beat-to-beat intervals of the heart, is a quantitative measure of autonomic regulation of the cardiovascular system. Low HRV derived from electrocardiogram (ECG) recordings is reported to be related to frailty in older adults. Recent advances in wearable technology offer opportunities to more easily integrate monitoring of HRV into regular clinical geriatric health assessments. However, signals obtained from ECG versus wearable photoplethysmography (PPG) devices are different, and a critical first step preceding their widespread use is to determine whether HRV metrics derived from PPG devices also relate to older adults’ functional status.
Objective:
The aim of this study was to investigate associations between HRV measured with a wrist-worn PPG device and validated clinical measures of functional status, including both objective and self-reported physical function, in a cohort of older adults living independently within a continuing care senior housing community. Our primary hypothesis was that lower HRV would be associated with lower physical function.
Methods:
We evaluated 41 participants from an ongoing study of older adults between 65 and 95 years of age. The assessments encompassed a thorough examination of domains typically included in a geriatric health evaluation. We collected HRV data with the Empatica E4 device and examined bivariate correlations between HRV quantified with the triangular index (HRV TI) and three widely used and validated measures of physical functioning – i.e., Short Physical Performance Battery (SPPB), Timed Up and Go (TUG), and Medical Outcomes Study - Short Form 36 (SF-36) physical composite scores. SPPB and TUG are objective measures while SF-36 is a subjective measure. We also present exploratory associations with age, comorbidities with the Cumulative Illness Rating Scale for Geriatrics (CIRS-G), body mass index (BMI), blood pressure, waist to hip ratio, and heart rate.
Results:
There were significant associations of HRV TI with SPPB (n=32; Spearman’s ρ = 0.394, p = 0.026); TUG (n=32; ρ = -0.515, p = 0.003); and SF-36 physical composite score (n=29; ρ = 0.503, p = 0.005). We also observed significant associations between HRV TI and the CIRS-G (n=32; ρ = -0.491, p = 0.004) and waist-to-hip ratio (n=32; ρ = -0.440, p = 0.012).
Conclusions:
HRV measured with a relatively novel wrist-worn PPG device was related to both objective (SPPB and TUG) and self-reported (SF-36 physical composite) measures of physical function. Future steps include longitudinal tracking of changes in both HRV and physical function, which will add important insights regarding the predictive value of HRV as a biomarker of functional outcomes in older adults.
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