Using Act24 To Assess Changes In Domain-specific Sedentary Time In Response To A Mhealth Intervention To Reduce Sedentary Screen Time

PURPOSE: ACT24 is a web-based previous-day recall that provides domain-specific estimates of sedentary behavior (SB) and physical activity (PA) that has been used in population-based studies. The present study examined the feasibility and sensitivity to change of ACT24 within an intervention study designed to reduce recreational sedentary screen time (rSST). METHODS: StandUPTV is a mHealth intervention that used the Multiphase Optimization Strategy framework to evaluate the efficacy of three theory-based strategies (LOCKOUT, TEXT, EARN) for reducing rSST among adults. In a factorial design, participants received a target to reduce rSST by 50% and were randomized to one of 8 combinations of the 3 strategies. Participants were sent two invitations to complete the ACT24 survey on random days within each of the assessment weeks (baseline, 8-, and 16-wks). ACT24 data were summarized into overall and domain-specific time in PA and SB. rSST was defined as leisure time television/videos and computer/internet use. We combined experimental groups and examined temporal changes in PA and SB using linear mixed-effect models (alpha <0.05). RESULTS: Participants (N = 110) had a mean (SD) age of 41 (11.7)y and BMI of 29.7 (7.8) kg/m2. At baseline, mean (SD) time in SB was 10.5 (3.5), PA was 5.5 (3.1), time in bed was 8.3 (1.5), and rSST was 3.3 (2.6) h/day. Of the 110 randomized, 80 completed the 16-week assessment. ACT24 completion rates were consistent across time-points (mean 1.5-1.7/person). There were no significant changes in total daily MET-hrs, SB, PA, or time in bed. There was a significant reduction in rSST of 0.82 (95%CI: 0.38, 1.3) h/day at 8-wks and 1.2 (0.75,1.65) h/day at 16-wks due to significant reductions in TV viewing (0.63 [0.27,0.99] h/day at 8-wks and 0.70 [0.33,1.1] h/day at 16-wks), and internet/computer use was significantly lower at 16-wks only (0.50 [0.18,0.80)h/day). Leisure time sitting and reading increased at 16-wks (0.31 [0.13,0.49] h/day). DISCUSSION: ACT24 was sensitive to change in domains of SB that were the primary intervention target (i.e., rSST), and not in unrelated domains. Future research should compare the sensitivity of ACT24 to an objective measure of SB and examine whether there were differential changes in domain-specific PA and SB by intervention component within the optimization trial. RO1CA239612