JMIR Publications

ABSTRACT

Background:

Consumer wearables are increasingly being integrated into health research for data collection. Though they are attractive to use, the accuracy of their photoplethysmography (PPG)-based measurements can be influenced by user characteristics, such as sex, age, BMI, and skin tone. Yet, our knowledge of the validity of these measurements in some populations, such as populations with darker skin tones and older adults, seems limited. This is concerning as uncorrected differences in measurement accuracy can lead to health disparities when consumer wearables measurements are being used more frequently. A potential cause for the gap in our knowledge on consumer wearable validity is the underrepresentation of some population groups in studies validating PPG-based consumer wearables.

Objective:

he aim of this scoping review is to map the representation of different sex, age, BMI, and skin tone groups in studies assessing the validity of PPG-based pulse rate, heart rate variability, blood pressure, peripheral blood oxygen saturation (SpO2), and respiratory rate measurements of consumer wearables. With this overview, we identified gaps in representation, and recommendations can be made to close these gaps.

Methods:

A literature search was conducted in Scopus, PubMed, and IEEE Xplore in June 2024 and July 2025. Papers were eligible if they assessed the validity of consumer wearable PPG-based measurements expressed as the agreement with a reference method. From the included papers, the study population distribution of sex, age, BMI, and Fitzpatrick scale was extracted. To evaluate the representation, the percentage of people in specific age, BMI, and skin tone groups was estimated based on reported means and standard deviations. The median percentage of participants in each population group, as well as the total percentage, is reported

Results:

After removal of duplicates, 734 papers were screened for eligibility. After title/abstract screening, 238 papers remained, of which 186 passed full text screening and were included in the review. Most of the studies (n=160) focused on pulse rate. Sex, age, BMI, and Fitzpatrick scale were reported by 95%, 94%, 54% and 19% of studies, respectively. The median% of older adults (>65 years), people with underweight (BMI <18.5 kg/m2), people with obesity (BMI ≥30 kg/m2), and people with darker skin tones (Fitzpatrick type V and VI) participating in a study was 0%.

Conclusions:

Based on our results, it can be concluded that older adults, and people with underweight, obesity, or darker skin tones are underrepresented in studies assessing the validity of consumer wearable PPG-based measurements. Future validation studies should focus more on the representativeness of the study population. This can be achieved by setting a benchmark for representativeness and including study population representatives in the study design process.