Impact of 3-Month Changes in Sedentary Time and Light-Intensity Physical Activity on Subjective Sleep Quality

Regular moderate-vigorous physical activity (MVPA) has been shown to improve sleep quality. However, little is known about whether reducing sedentary time (i.e., replacing sitting with standing) or increasing light-intensity physical activity (LPA) may also improve sleep. PURPOSE: To examine whether 3-month changes in objectively measured sedentary time and LPA are associated with subjective sleep quality. METHODS: Participants (N=632, 72.3% female, 71.2% white, 44.6 ± 11.2 years of age) were recruited from 24 worksites in the Phoenix and Minneapolis regions to participate in the multi-component cluster randomized controlled trial ‘Stand & Move at Work,’ to reduce sitting and increase LPA in the workplace. Participants wore an activPAL accelerometer continuously for seven consecutive days to assess sedentary (i.e., sitting/lying down) and LPA (stepping at < 100 steps/min) behaviors. Daily logs were used to separate data into work and non-work hours and behaviors were standardized to 8hr workdays. The Pittsburgh Sleep Quality Index (PSQI) was administered concurrently with the activPAL at baseline and at 3 months to assess subjective sleep quality (lower scores = better sleep quality). Mixed-effects regression models adjusted for worksite clustering and age, gender, race, job type, body mass index (BMI), and MVPA. RESULTS: Participants spent 333.1 ± 78.0 min/8hr workday and 30.7 ± 14.8 min/8hr workday in sedentary and LPA behaviors at baseline, respectively. Overall, sedentary time was reduced by 33.6 ± 13.6 min/8hr workday and LPA was increased by 0.1 ± 0.9 min/8hr workday. Increases in LPA were associated with 3-month improvements in PSQI sleep latency (b[se]= -.009 [.20], p=.025). No other changes in sedentary or LPA behaviors were associated with PSQI changes. CONCLUSION: Workplace interventions targeting reductions in sedentary behavior may be effective for improving sleep onset, but not other aspects of sleep quality. Future interventions should examine longer term follow-up periods, assess sleep objectively, and incorporate interventions that target sedentary time and LPA both during and outside of work hours.