2. Platz Fabian Schwendinger (Universität Basel):
Accelerometer-Based Physical Activity Surveillance in Healthy and Diseased Adults
Background: Accelerometers provide previse physical activity (PA) assessment, yet data quality depends on valid wear protocols and interpretability. Continuous, cut-point-free metrics capture the full 24-hour intensity spectrum, distinguishing PA volume from intensity. However, their interpretability remains limited without reference values, and relative intensity measures are lacking. This PhD project aimed to advance accelerometer-based PA surveillance by refining methodology, enhancing interpretability through reference values, and exploring how PA volume, intensity, and duration relate to health outcomes across healthy and diseased populations.
Methods: Data from the COmPLETE study (healthy adults and patients with heart failure) involved 14-day wrist-worn accelerometry and cardiopulmonary exercise testing. Additional analyses used 7-day accelerometer data from the 2011–2014 NHANES cohort. Metrics from the R-package GGIR included average acceleration (AvAcc, PA volume) and intensity gradient (IG, PA intensity), expressed in absolute (_ABS) and relative (_REL) terms, plus PA fragmentation (MXRATIO). Associations with cardiorespiratory fitness and mortality were examined using regression and Cox proportional hazards models.
Results: Cut-point-based metrics frequently misclassified PA intensity. Both AvAcc_ABS and IG_ABS independently predicted cardiorespiratory fitness, with intensity showing stronger associations than volume. Reference values and centile curves were generated for PA metrics. IG_ABS showed curvilinear inverse associations with all-cause and cardiovascular mortality, with intensity emerging as the primary driver.
Conclusion: This thesis advances accelerometer methodology, supporting cut-point-free metrics for accurate, interpretable, and comparable PA assessment. Intensity appears key to health benefits, and new reference values enable practical application in research, clinical, and public health settings.
