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BACKGROUND: This study aims to describe the relationships between physical activity (PA), body composition and multimorbidity over 10 years. METHOD(S): Participants (N=373; 49% women; average age 61.3+/-6.7 years) were followed for 10 years. Multimorbidity was defined by self-report as the presence of two or more of 12 listed chronic conditions. PA (steps-per-day) at baseline was assessed by pedometer, handgrip strength (HGS) by dynamometer and appendicular lean mass (ALM) and total body fat mass by dual x-ray absorptiometry . Relative HGS and ALM were calculated by dividing each body mass index (BMI). Regression cubic splines were used to assess evidence for a non-linear relationship. RESULT(S): After 10 years, 45% participants had multimorbidity. There was a non-linear relationship between PA and multimorbidity - PA was associated with lower multimorbidity risk among individuals who engaged in <10,000 steps-per-day (RR=0.91, 95% CI: 0.85, 0.97, per 1000 steps-per-day), but not among those who participated in >=10,000 steps-per-day (RR=1.04, 95% CI: 0.93, 1.09, per 1000 steps-per-day). Higher BMI (RR=1.05, 95% CI: 1.02, 1.08, per kg/m 2) and fat mass (RR=1.03, 95% CI: 1.01, 1.04, per kg), and lower relative HGS (RR=0.85, 95% CI: 0.77, 0.94, per 0.1 psi/kg/m 2) and ALM (RR=0.93, 95% CI: 0.88, 0.98, per 0.1 kg/kg/m 2) were linearly associated with a higher risk of multimorbidity. Absolute HGS and ALM were not significantly associated with multimorbidity. DISCUSSION: These findings highlight the potential clinical importance of maintaining adequate levels of PA and of reducing adiposity and maintaining muscle function for minimising the risk of multimorbidity in older adults.Copyright © The Author(s) 2021. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

This study aims to assess whether older adults with low muscle mass or strength, in the presence of obesity, have an increased risk of knee (TKR) and hip replacement (THR) over 13 years. 1082 community-dwelling older adults (51% women; mean age 62.9 +/- 7.5 years) were studied at baseline and multiple time points over 13 years. The incidence of TKR and THR was determined by data linkage to National Joint Replacement Registry. Appendicular lean and fat mass were measured using DXA. Lower-limb muscle strength (LMS) was assessed by dynamometer. Low muscle mass and strength were defined as the lowest sex-specific tertiles for appendicular lean mass (adjusted for height and total body fat mass) and lower-limb strength, respectively. Obesity was defined as the highest sex-specific tertile for total body fat mass. Competing risk regression models were used to estimate the sub-distribution hazard ratio (SHR) for TKR and THR. Over 13 years of follow-up, 6.8% (n = 74/1082) of the participants had a TKR and 4.7% (n = 50/1066) had THR. Participants with the combination of obesity and low muscle strength (SHR 3.36, 95% CI 1.50, 7.53) but low muscle mass (SHR 1.11, 95% CI 0.52, 2.40) had a significantly increased risk of TKR, compared to individuals with neither obesity nor low muscle mass/strength. However, obesity with low muscle strength did not lead to a significantly greater risk of TKR compared to having low muscle strength or obesity alone. There was no evidence for an association between obesity with low muscle mass or strength and THR (all p > 0.05). This finding suggests that combining muscle and fat assessments to predict the future risk of TKR is no better than each condition on its own.Copyright © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Objective: Traditionally, analysis has focused on examining how risk factors for falls differ between individuals (between-person comparison). Less well recognized is how variability in risk factors over time within the same individual (within-person comparison) is associated with falls risk. To describe the associations between falls risk, and between-person and within-person variability in 25-hydroxyvitamin D (25OHD), physical activity (PA), knee pain and dysfunction in community-dwelling older people. Material(s) and Method(s): Data for 1053 participants (51% women; mean age 63+/-7. 4 years) studied at baseline, 2. 5, 5, and 10 years were analysed. Falls risk (Z-score) was measured using the validated Physiological Profile Assessment. Knee pain and dysfunction were assessed using the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC). Moderate and vigorous PA (MVPA) was measured using accelerometer. Linear mixed effect regression models, with adjustment for confounders, were used to estimate the association between falls risk and between-person and within-person variability in PA, 25OHD and WOMAC score. Result(s): Between-person effects showed that 10-year average falls risk was lower in participants who had a higher 10-year average 25OHD (beta=-0. 005 per nmol/l, 95% CI:-0. 008,-0. 002, P<0. 001), log-MVPA (beta=-0. 16 per minute, 95% CI:-0. 22,-0. 10, P<0. 001) and lower mean WOMAC score (beta=0. 005 per-unit score, 95% CI: 0. 003, 0. 01, P<0. 001). Within-person effects showed that a higher falls risk at any time-point was associated with higher than average WOMAC score (beta=0. 002 per-unit score, 95% CI: 0. 0003, 0. 004, P=0. 025) and lower than average log-MVPA (beta=-0. 15 per minute, 95% CI:-0. 24,-0. 06, P=0. 003), but not 25OHD, at the same time-point. Conclusion(s): Within-person analysis showed that at time-points when participants had higher pain and dysfunction and lower MVPA, they also had a higher falls risk. This sup-ports cli