Measuring change in trials of physical activity interventions: a comparison of self-report questionnaire and accelerometry within the PACE-UP trial

Abstract

Background: Few trials have compared estimates of change in physical activity (PA) levels using51 self-reported and objective PA measures when evaluating trial outcomes. The PACE-UP trial offered52 the opportunity to assess this, using the self-administered International Physical Activity53 Questionnaire (IPAQ) and waist-worn accelerometry.54 Methods: The PACE-UP trial (N=1023) compared usual care (n=338) with two pedometer-based55 Walking interventions, by post (n=339) or with nurse support (n=346). Participants wore an56 accelerometer at baseline and 12 months and completed IPAQ for the same 7-day periods. Main57 outcomes were weekly minutes, all in ≥10 minute bouts as per UK PA guidelines of: i) accelerometer 58 moderate-to-vigorous PA (Acc-MVPA) ii) IPAQ moderate + vigorous PA (IPAQ-MVPA) and iii)59 IPAQ walking (IPAQ-Walk). For each outcome, 12 month values were regressed on baseline to60 estimate change.61 Results: Analyses were restricted to 655 (64%) participants who provided data on all outcomes at62 baseline and 12 months. Both intervention groups significantlyincreased their accelerometryMVPA63 minutes/week compared with control: postal group 42 (95% CI 22, 61), nurse group 43 (95% CI 24,64 63). IPAQ-Walk minutes/week also increased: postal 57 (95% CI 2, 112), nurse 43 (95% CI -11, 97)65 butIPAQ-MVPAminutes/weekshowednon-significantdecreases:postal-11(95%CI-65,42),nurse66 -34 (95% CI -87, 19).67 Conclusions: Our results demonstrate the necessity of using a questionnaire focussing on the68 activities being altered, as with IPAQ-Walk questions. Even then, the change in PA was estimated69 with far less precision than with accelerometer. Accelerometry is preferred to self-report70 measurement, minimising bias and improving precision when assessing effects of a walking71 intervention.