Presenting Author:

Whitney Welch, Ph.D.

Principal Investigator:

Juned Siddique

Department:

Preventive Medicine

Keywords:

exercise, lifestyle, adults, participation, behavior

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

PH50 - Public Health & Social Sciences

Environmental factors moderate the effect of a physical activity intervention

Purpose: To identify whether natural environmental factors such as season, weather conditions, and day length moderate the effect of a physical activity intervention in Chicago. Methods: Participants (N=204, 77% female, age=33±11y, BMI=28.2±7.1 kg/m2) in the Make Better Choices (MBC) Study were randomized to one of two activity-related intervention arms: 1) an increase physical activity arm with a goal to increase moderate to vigorous physical activity (MVPA) to 60 min/day, or 2) a decrease sedentary behavior arm with a goal to decrease leisure time sedentary screen-time to less than 90 min/day. Participants were asked to wear an accelerometer-based activity monitor for five weeks: a two-week baseline assessment phase and a three-week intervention follow-up phase. Activity monitor data were used to estimate min/day spent in MVPA. Average daily temperature and day length for Chicago were obtained from the National Climatic Data Center and combined with the MBC accelerometer data. Linear mixed-effects models were used to determine whether these environmental factors moderated the effect of the MBC intervention on MVPA. Moderation was assessed by estimating a three-way time by treatment arm by environmental factor interaction. Separate models were fit for season, daily average temperature, and day length. Models for temperature included main effects for day length; models for day length included a main effect for temperature. Results: There was a significant moderating effect of season on MVPA such that the difference between treatment arms at follow-up was 10.4 minutes greater in the summer than in the winter (95% CI: 1.1, 19.6; p=0.029). When specific natural environmental factors were examined, there was a significant moderating effect of daily temperature such that every 10° increase in temperature resulted in a 1.6 min/day difference (p-value=0.015) in MVPA between treatment arms at follow-up. Additionally, there was a significant moderating effect of day length such that every additional hour of daylight was associated with a 2.0-minute difference (p-value=0.002) in MVPA between treatment arms at follow-up. Conclusion: Results reveal day length and temperature have a significant moderating effect on change in MVPA during a multi-component physical activity intervention. This suggests that when designing physical activity interventions in adults, strategies to overcome environmental barriers should be considered.