Self-reported and device-measured population trends in adherence to physical activity guidelines – do they compare?

Introduction: Monitoring secular trends in physical activity (PA) is essential to track progress towards the UNs 2030 sustainable development physical activity goal. PA questionnaires (PAQs) are standard in tracking physical activity worldwide. Albeit their practicality and feasibility for surveillance purposes, PAQs have inherent limitations. In contrast, devices are not prone to the same biases as PAQs. An important and complex topic relates to the comparison between PAQ- and device-measured PA and whether they provide similar prevalence data on trends in PA. Purpose: To explore whether PAQs and devices provide the same results when assessing secular trends in physical activity. Methods: The Norwegian Physical Activity Surveillance Study (NPASS) is a repeated cross-sectional study of population level PA in Norwegian 20-85-year old’s. Adherence to PA guidelines was assessed concurrently by the IPAQ-short and 7-day actigraphy. Results: We observed a negative secular change in self-reported adherence to PA guidelines, from 67% in 2008-09 to 65% in 2014-15, with individuals in 2014-15 having 15% lower odds of meeting the PA guidelines compared to individuals in 2008-09 (OR: 0.85, 95% CI: 0.76 – 0.96). In contrast, we observed a positive secular change in device-measured adherence to PA guidelines, from 68% in 2008-09 to 73% in 2014-15, corresponding to 26% higher odds of meeting the PA guidelines in 2014-15 compared with 2008-09 (OR: 1.26. 95% CI: 1.12 – 1.42). Conclusion: Secular trends in PA differ across measurement methods. Self-reported physical activity indicates no or a negative change across the two timepoints, while device-measured physical activity indicates a positive trend. Practical implications: Trends in adherence to PA guidelines differ between assessment methods which needs to be considered when interpreting such data. Funding: NPASS is funded by the Norwegian Directorate of Health, the Public Health Institute of Norway, and the Norwegian School of Sport Sciences.