Longitudinal Associations Of Adiposity And Grip Strength With Physical Activity Assessed With Wrist-worn Accelerometers In 84,779 Adults

Abstract

PURPOSE: To determine the longitudinal associations of body mass index (BMI), waist circumference (WC) and grip strength (GS) with objectively measured physical activity (PA) in adults. METHODS: This study utilized data from the UK Biobank study, an ongoing prospective cohort of over half a million UK adults aged 40-69yrs at recruitment (2006 to 2010). Each participant underwent baseline measurements of BMI (kg/m2), WC (cm) and GS (kg). GS was measured using a hand dynamometer. Values from the two hands were averaged. Between 2013 and 2015, a sub-sample of over 100,000 participants each wore a tri-axial accelerometer on the dominant wrist for 7 days. Measurements taken at baseline were not repeated during the follow-up accelerometer protocol. Mean acceleration levels were calculated, and moderate-to-vigorous PA (MVPA) was estimated as time when acceleration was above 125mg. BMI, WC and GS were standardized, and PA outcomes were log-transformed. RESULTS: A total of 84,812 participants (46,947 women) with ≥72 hours of wear and no missing covariates were included in the analysis. The median follow-up was 5.7 years (interquartile range: 4.9-6.5). Using multiple linear regression adjusted for GS and various potential confounders (demographic, lifestyle, disease status, seasonality), every 1 standard deviation increase in BMI and WC was associated with 0.071 (95% confidence interval [CI]: -0.073, -0.069) and 0.070 (95% CI: -0.073, -0.068) lower log of mean acceleration at follow-up, respectively, in women: in men, BMI (b: -0.066; CI: -0.069, -0.063) and WC (b: -0.076; CI: -0.079, -0.073). Positive associations were found between baseline GS and follow-up acceleration levels after adjusting for confounders and BMI, in women (b: 0.013; CI: 0.010, 0.01) and men (b: 0.004; CI: 0.001, 0.007). Marginal means (adjusted for confounders) of follow-up acceleration were lower in individuals with higher adiposity levels and/or lower GS at baseline. Similar results were observed with MVPA as an outcome. CONCLUSIONS: BMI, WC and GS at baseline predicted objectively measured PA at follow-up. Findings of our study provide compelling justification for interventions and policies to focus on improving body composition and muscle strength to increase or prevent decline in PA at the population level.