Physical Activity Trackers: Umbrella Analysis Finds Significant Positive Impact on Walking, Weight Loss

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Activity trackers may in fact be returning positive and measurable health benefits, according to an umbrella review published in the Lancet Digital Health on August 1, 2022.

The systematic review of meta-analyses, the highest-level review of published research, found that use of wearable step trackers, activity-tracking smartwatches, and pedometers improved physical activity, body composition, and fitness, equaling 40 minutes of additional walking per day and weight loss of more than 2 lbs. The increased activity was observed across age groups and clinical and nonclinical populations.

The number of wearable activity trackers shipped globally between 2014 and 2020 increased by 1444%, the review authors write, paralleled by the rapid expansion of research examining their utility for improving physical activity levels. But "despite their prima-facie promise," there is widespread scientific, medical, and general skepticism about the effectiveness of these wearables, according to the researchers.

Led by Proffessor Carol Maher, a research professor in the Alliance for Research in Exercise, Nutrition, and Activity, University of South Australia in Adelaide, the research team says that leading concerns focus on the accuracy of the technologies, their potential to fuel obsessive behaviors and eating disorders, and to perpetuate health inequities.

The number of wearable activity trackers shipped globally between 2014 and 2020 increased by 1444%, the review authors write, paralleled by the rapid expansion of research examining their utility for improving physical activity levels.

Given the "now voluminous body of evidence" regarding the wearable activity trackers, the investigators set out to curate the highest quality evidence published that examines the trackers' effectiveness for increasing physical activity and also for any resulting physiologic and psychosocial outcomes.

The team searched 7 databases (Embase, MEDLINE, Ovid Emcare, Scopus, SPORTDiscus, the Cochrane Library, and Web of Science) from database inception to April 2021. Systematic reviews of primary studies using activity trackers as interventions vs to monitor outcomes, and reporting physical activity, physiological, or psychosocial outcomes were eligible for inclusion.

From an original 2382 records returned from the database search, 39 systematic reviews comprising 390 component studies and 163 841 participants, were eligible. The majority of the reviews (26) were published since 2018:

• Median number of studies in each review, 14
• Median number of participants in each systematic review, 2003 (range 167 to 73 440)
• Half (20) of reviews focused on clinical populations (eg, type 2 diabetes [T2D], chronic obstructive pulmonary disease [COPD], overweight/obesity), 8 on nonclinical populations, and 11 on both.
• The systematic reviews focused on physical activity (either alone [n=26] or combined with other outcomes [n=6), weight loss (n=4), weight control (n=1), chronic disease management (n=1), and pain and disability (n=1).

Findings

Physical activity

Wearable activity trackers increased physical activity outcomes with effect sizes in the order of 0.28 to 0.57 (first and third quartiles, respectively). Increases in specific metrics included:

• Increased daily step count (mean effect size 0.6 [medium effect])
• Increased physical activity/energy expenditure (mean effect size 0.4 [medium])
• Increased moderate-to-vigorous physical activity (MVPA) (mean effect size 0.3 [small])

Further analysis found that interventions using wearable activity trackers increased step counts on average by approximately 1800 steps per day, walking time by approximately 40 minutes per day, and MVPA by ~6 minutes per day.

Physiologic outcomes

The effects of wearable activity trackers on physiologic outcomes are based on 17 systematic reviews and while the results were in “favourable directions,” the researchers write, effect sizes were small and not often statistically significant.

The strongest evidence for improvement was seen in moderate effects for body weight (–0·5 kg to –1·5 kg), waist circumference (–1·5 cm), BMI (–0·5 kg/m² ), and aerobic capacity (1·7 mL/kg/min improvement in VO₂ max. Evidence was minimal for an effect on blood pressure and heart rate, cholesterol, triglyceride levels, glycosylated hemoglobin, or fasting plasma glucose.

Considering all studies, 41% showed significant favourable associations, 57% non-significant associations, and 3% significant unfavourable associations.

Psychosocial outcomes

Overall, Maher and colleagues report, there was little evidence that interventions based on activity trackers affected quality of life. One review looking at effects on disability and pain reported non-significant medium effect sizes toward a decrease in disability and pain.

Consistent effects

Population. The investigators report that physical activity outcomes consistently improved in children, adults, and older adults with similar effect sizes and also improved in healthy and all the clinical populations represented in the meta-analysis. Effects on body composition were seen in healthy populations as well as in those with T2D, COPD, CVD, and overweight/obesity.

Device type. When the team compared the results by device type (ie, pedometer-based interventions and consumer activity-tracker-based interventions), results were also broadly consistent.

Duration of effect. Effect duration was examined in 3 systematic reviews with strong effects on step counts at 4 to 6 months and smaller yet still statistically significant effects up to 4 years. Long term there were small nonsignificant results observed on body composition.

The authors suggest this is the first umbrella review to examine the efficacy of wearable activity-tracker-based interventions. They write in their conclusion that evidence across the large number of meta-analyses included suggests “wearable trackers consistently outperformed controls for physical activity outcomes with moderate effect sizes.”

The interventions also support modest weight loss in a wide variety of populations across age and clinical disposition "and gains appear to be durable for at least 6 months. Effects on other physiologic and psychosocial outcomes are small and often nonsignificant" although on the latter the findings suggested mostly positive effects.

There is sufficient evidence to recommend the use of wearable activity trackers at least as an adjunct to programmes aiming to increase physical activity, they conclude.

Among the limitations the research team notes is that umbrella reviews by nature are limited by constraints of the systematic reviews and meta-analyses it captures. Even though the systematic reviews they retrieved did cover a wide range of clinical populations, they emphasize that these populations were not exhaustive.

Reference: Ferguson T, Olds T, Curtis R, et al. Effectiveness of wearable activity trackers to increase physical activity and improve health: a systematic review of systematic reviews and meta-analyses. The Lancet Digital Health. 2022; 4(8):e615 doi:10.1016/S2589-7500(22)00111-X