Individual and joint trajectories of change in bone, lean mass and physical performance in older men

Peggy M Cawthon,Deborah M Kado,Jodi Lapidus,Jane A Cauley,Steven R Cummings,Kristine E Ensrud,Andrew R Hoffman,Marcia L Stefanick,Nancy E Lane,Rebecca Drieling,Thomas M Gill,Neeta Parimi,Charles E Mcculloch,Eric S Orwoll,Lisa Langsetmo

doi:10.1186/s12877-020-01560-5

Abstract

BackgroundDeclines in bone, muscle and physical performance are associated with adverse health outcomes in older adults. However, few studies have described concurrent age-related patterns of change in these factors. The purpose of this study was to characterize change in four properties of muscle, physical performance, and bone in a prospective cohort study of older men.MethodsUsing repeated longitudinal data from up to four visits across 6.9 years from up to 4681 men (mean age at baseline 72.7 yrs. ±5.3) participating in the Osteoporotic Fractures in Men (MrOS) Study, we used group-based trajectory models (PROC TRAJ in SAS) to identify age-related patterns of change in four properties of muscle, physical performance, and bone: total hip bone mineral (BMD) density (g/m2) and appendicular lean mass/ht2 (kg/m2), by DXA; grip strength (kg), by hand dynamometry; and walking speed (m/s), by usual walking pace over 6 m. We also described joint trajectories in all pair-wise combinations of these measures. Mean posterior probabilities of placement in each trajectory (or joint membership in latent groups) were used to assess internal reliability of the model. The number of trajectories for each individual factor was limited to three, to ensure that the pair-wise determination of joint trajectories would yield a tractable number of groups as well as model fit considerations.ResultsThe patterns of change identified were generally similar for all measures, with three district groups declining over time at roughly similar rates; joint trajectories revealed similar patterns with no cross-over or convergence between groups. Mean posterior probabilities for all trajectories were similar and consistently above 0.8 indicating reasonable model fit to the data.ConclusionsOur description of trajectories of change with age in bone mineral density, grip strength, walking speed and appendicular lean mass found that groups identified by these methods appeared to have little crossover or convergence of change with age, even when considering joint trajectories of change in these factors.

Highlights

Declines in bone, muscle and physical performance are associated with adverse health outcomes in older adults
In panel A, the trajectories for grip strength are shown for participants within the low bone mineral density (BMD) trajectory, the medium BMD trajectory and the high BMD trajectory
Some of the groups identified were rather small: only 159 men (3.6% of the total men in the model) were in the high BMD/low grip strength trajectory and only 179 men (4.0% of the total men in the model) were in the high BMD/high grip strength group; the most common placement was in the medium BMD/medium grip strength trajectory (N = 1127, 25.4% of the total men in the model)

Summary

Introduction

Muscle and physical performance are associated with adverse health outcomes in older adults. Muscle and physical performance may be associated with unfavorable outcomes (such falls, fractures, mortality and disability) [14,15,16,17], few studies have investigated the process of change in these factors concurrently. We have described distinct trajectories of bone loss with age, demonstrating that the character of change is important, and that declines increases fracture risk and mortality [2, 14]. Our ultimate goal is to test the hypothesis that when age-related deterioration in bone, muscle and physical performance occur in parallel their combined effects magnify the risk of poor functional and health outcomes among communitydwelling older men

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