Assessment of activity tracker wear-time in longitudinal measurement of physical activity in children and young people with CF

Physical activity (PA) is recommended for all children and young people with CF (CYPwCF), however levels of participation vary between and within individuals. Studies collecting short-term PA data from research trackers are often limited by insufficient wear-time, and fail to reflect variations related to weather/season, weekday/weekend, school holiday, or hospital admission. CYP have reported that comfort, design and feedback features are important, thus commercially available activity trackers with these features may enable better measurement of individual PA patterns over time. Wear-time data were collected from CYPwCF (6-16yrs) asked to wear a Fitbit AltaHR as much as possible during the first 30days of participation in a longitudinal study. From literature, ≥8 recorded daytime hours were considered valid for data analysis with 3-9days providing reliable measurement of PA levels. A total of 1,950days were analysed from 65CYPwCF (median:9.6yrs, 36male). In 30days, CYPwCF contributed mean±SD 16±8days valid for data analysis (range:0-28days). 49/65 (75%) provided >9days (median:21, range:9-28days), 7/65 (11%) provided 3-8days (med:5, range:3-8), and 9/65 (14%) yielded 0-2days, 4/9 due to problems with data synchronising. Days of valid data contributed by participants varied, but 86% easily exceeded traditional thresholds for PA data analysis within 30days. Results suggest that commercially available activity trackers may prove useful in assessing longitudinal patterns of PA in CYPwCF. Further research will continue to evaluate minimal wear-time for accurately and reliably characterising patterns of PA taking account of seasonal and circumstantial changes.