Examining mediators of intervention efficacy in a randomised controlled m-health trial to improve physical activity and sleep health in adults

Abstract

Objectives: Examining mediators of intervention efficacy in an m-health intervention targeting physical activity and sleep in 160 Australian adults.

Design: Nationwide randomised controlled trial.

Main outcome measures: Moderate- and vigorous-intensity physical activity (MVPA), assessed using the Active Australia Questionnaire; sleep quality (Pittsburgh Sleep Quality Index); and sleep hygiene practices (Sleep Hygiene Index). Hypothesised psychosocial (e.g. self-efficacy) and behavioural (i.e. MVPA, sleep quality, sleep hygiene) mediators were tested on primary endpoint data at 3 months using bias-corrected bootstrapping (PROCESS 2 for SPSS). All outcomes and mediators were assessed using self-report.

Results: At three months, the intervention had significantly improved sleep quality (d = 0.48, 95% CI: −2.26, −0.33, p = 0.009) and sleep hygiene (d = 0.40, 95% CI: −3.10, −0.19, p = 0.027). Differences in MVPA were not significant (d = 0.24, 95% CI: −35.53, 254.67, p = 0.139). Changes in MVPA were mediated by self-efficacy, perceived capability, environment, social support, intentions and planning, some of which showed inconsistent mediation (suppression). None of the hypothesised psychosocial factors mediated sleep outcomes. Changes in sleep hygiene mediated changes in sleep quality.

Conclusions: Several psychosocial factors mediated changes in physical activity but not in sleep outcomes. Mediation effects of sleep hygiene on sleep quality highlight the importance of providing evidence-based strategies to improve sleep quality.

Keywords:

• Physical activity
• sleep quality
• sleep hygiene
• psychosocial determinants
• mediation analysis

Disclosure statement

The authors declare no conflicts of interest.

Additional information

Funding

This work was supported by the National Heart Foundation of Australia under Grant ID’s 100029, 100629 and 100427; the National Health and Medical Research Council (NHMRC) under Fellowship ID APP1141606; and the Australian Research Council (ARC) under Grant number FT140100399.