Do smartphone applications and activity trackers increase physical activity in adults? Systematic review, meta-analysis and metaregression.

OBJECTIVE: To determine the effectiveness of physical activity interventions involving mobile applications (apps) or trackers with automated and continuous self-monitoring and feedback. DESIGN: Systematic review and meta-analysis. DATA SOURCES: PubMed and seven additional databases, from 2007 to 2020. STUDY SELECTION: Randomised controlled trials in adults (18-65 years old) without chronic illness, testing a mobile app or an activity tracker, with any comparison, where the main outcome was a physical activity measure. Independent screening was conducted. DATA EXTRACTION AND SYNTHESIS: We conducted random effects meta-analysis and all effect sizes were transformed into standardised difference in means (SDM). We conducted exploratory metaregression with continuous and discrete moderators identified as statistically significant in subgroup analyses. MAIN OUTCOME MEASURES: Physical activity: daily step counts, min/week of moderate-to-vigorous physical activity, weekly days exercised, min/week of total physical activity, metabolic equivalents. RESULTS: Thirty-five studies met inclusion criteria and 28 were included in the meta-analysis (n=7454 participants, 28% women). The meta-analysis showed a small-to-moderate positive effect on physical activity measures (SDM 0.350, 95% CI 0.236 to 0.465, I2=69%, T 2=0.051) corresponding to 1850 steps per day (95% CI 1247 to 2457). Interventions including text-messaging and personalisation features were significantly more effective in subgroup analyses and metaregression. CONCLUSION: Interventions using apps or trackers seem to be effective in promoting physical activity. Longer studies are needed to assess the impact of different intervention components on long-term engagement and effectiveness.

Gut feelings: A randomised, triple-blind, placebo-controlled trial of probiotics for depressive symptoms.

BACKGROUND: Depression is the leading cause of disability worldwide; with evidence suggesting that decreased gut barrier function and inflammation are correlated with depressive symptoms. We conducted a clinical trial to determine the effect of consumption of probiotic supplements (Winclove's Ecologic® Barrier) on depressive symptoms in a sample of participants with mild to severe depression. METHOD: 71 participants were randomly allocated to either probiotic or placebo, which was, consumed daily over eight weeks. Pre- and post-intervention measures of symptoms and vulnerability markers of depression as well as gut microbiota composition were compared. Clinical trial participants were also compared on psychological variables and gut microbiota composition to a non-depressed group (n = 20). RESULTS: All clinical trial participants demonstrated improvement in symptoms, suggesting non-specific therapeutic effects associated with weekly monitoring visits. Participants in the probiotic group demonstrated a significantly greater reduction in cognitive reactivity compared with the placebo group, particularly in the mild/moderate subgroup. Probiotics did not significantly alter the microbiota of depressed individuals, however, a significant correlation was found between Ruminococcus gnavus and one depression metric. LIMITATIONS: There was a high attrition rate, which may be attributed to weekly monitoring visits. Additionally, modulation of the gut microbiota may need more specific testing to distinguish subtle changes. CONCLUSIONS: While microbiota composition was similar between all groups, probiotics did affect a psychological variable associated with susceptibility to depression. Further research is needed to investigate how probiotics can be utilised to modify mental wellbeing, and whether they can act as an adjunct to existing treatments.