The Relation of Activity Patterns with Incident Slow Gait Speed over 4 Years in Adults with Knee Osteoarthritis: Data from the Osteoarthritis Initiative.

OBJECTIVE:The purpose of this study was to describe activity patterns in adults with knee osteoarthritis (OA) and to examine the relation of patterns with incident slow gait speed over 4 years. DESIGN:Using data from the Osteoarthritis Initiative, we included adults with or at high risk of knee OA who walked > 1.0 m/s during a 20-meter walk at baseline, i.e., did not have slow gait speed. To determine activity patterns, we reduced the dimensions of accelerometer data (ActiGraph GTM1) using a multidimensional Multilevel Functional Principal Components Analysis to calculate between-subject principal component (PC) scores. We estimated the association of the top and bottom tertiles' PC scores with incident slow gait speed over 4 years (risk ratios with 95% confidence intervals) referenced to the middle tertile, adjusting for potential confounders. RESULTS:We identified four activity patterns (PCs): 1) high activity, 2) high evening activity, 3) high morning and evening activity, and 4) very high morning activity. Those whose daily activity patterns best matched with the pattern PC2 or PC4, were found to have 0.60 [0.37, 0.96] and 0.39 [0.22, 0.71] times the risk of developing slow gait speed, respectively; while those whose daily activity patterns least matched PC3, were found to have 1.77 [1.19, 2.62] times the risk. CONCLUSIONS:Daily activity patterns may be related to the development of slow gait speed in adults with or at risk for knee OA. TRIAL REGISTRATION:NCT00080171.