Accuracy Of Mobile HRV Devices For Measuring RMSSD

There are a number of commercially available heart rate variability (HRV) mobile devices that provide a measure of root mean square of successive R-R differences (RMSSD). However, their accuracy compared to electrocardiography (ECG) remains questionable. PURPOSE: To compare a range of mobile devices to ECG for measuring RMSSD under a variety of conditions. METHODS: This review was conducted in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) statement guidelines. Articles published before July 22, 2016 were located using searches of the Physical Education Index (n=1,007), PubMed (n=1,145), Scopus (n=1,562), and SPORTDiscus (n=2,137) online databases using combinations of the terms: heart rate variability, HRV, valid, and validity. Duplicate publications were removed, yielding 4,686 original records for review. In addition, three publications were identified through a manual reference search. All studies included in the meta-analysis were peer reviewed and published in English. Each study effect size (ES) was calculated as the difference between the RMSSD measures recorded from the mobile device compared to ECG, divided by the pooled standard deviation and adjusted for small sample bias. Random-effects models were used to aggregate a mean ES and 95% confidence intervals (CI). In addition, a multi-level model was used to account for the nesting of multiple effects within a single study. RESULTS: The cumulative results from 35 effects extracted from 14 articles published between 2005 and 2016 indicate no difference between the mobile devices and ECG for RMSSD measures (ES = -0.0040, 95% CI = -0.0687, 0.0608, p = 0.9039). The multi-level model yielded similar results (ES=-0.0040, 95% = -0.0687, 0.0608, p=0.9059). The number of effects obtained from each studied ranged from 1 to 12 (mean=2.92, standard deviation=3.00). We observed minimal heterogeneity among our effects (Q = 4.516, p=0.99; I2=0%), with 100% of the observed heterogeneity explained by sampling error. CONCLUSIONS: These results suggest that mobile HRV devices provide similar measures of RMSSD compared to ECG.