Terminal decline in objective and self-reported measures of motor function before death: 10 year follow-up of Whitehall II cohort study

Abstract

Objectives: To examine multiple objective and self-reported measures of motor function for their associations with mortality.

Design: Prospective cohort study.

Setting: UK based Whitehall II cohort study, which recruited participants aged 35-55 years in 1985-88; motor function component was added at the 2007-09 wave.

Participants: 6194 participants with motor function measures in 2007-09 (mean age 65.6, SD 5.9), 2012-13, and 2015-16.

Main outcome measures: All cause mortality between 2007 and 2019 in relation to objective measures (walking speed, grip strength, and timed chair rises) and self-reported measures (physical component summary score of the SF-36 and limitations in basic and instrumental activities of daily living (ADL)) of motor function.

Results: One sex specific standard deviation poorer motor function in 2007-09 (cases/total, 610/5645) was associated with an increased mortality risk of 22% (95% confidence interval 12% to 33%) for walking speed, 15% (6% to 25%) for grip strength, 14% (7% to 23%) for timed chair rises, and 17% (8% to 26%) for physical component summary score over a mean 10.6 year follow-up. Having basic/instrumental ADL limitations was associated with a 30% (7% to 58%) increased mortality risk. These associations were progressively stronger when measures were drawn from 2012-13 (mean follow-up 6.8 years) and 2015-16 (mean follow-up 3.7 years). Analysis of trajectories showed poorer motor function in decedents (n=484) than survivors (n=6194) up to 10 years before death for timed chair rises (standardised difference 0.35, 95% confidence interval 0.12 to 0.59; equivalent to a 1.2 (men) and 1.3 (women) second difference), nine years for walking speed (0.21, 0.05 to 0.36; 5.5 (men) and 5.3 (women) cm/s difference), six years for grip strength (0.10, 0.01 to 0.20; 0.9 (men) and 0.6 (women) kg difference), seven years for physical component summary score (0.15, 0.05 to 0.25; 1.2 (men) and 1.6 (women) score difference), and four years for basic/instrumental ADL limitations (prevalence difference 2%, 0% to 4%). These differences increased in the period leading to death for timed chair rises, physical component summary score, and ADL limitations.

Conclusion: Motor function in early old age has a robust association with mortality, with evidence of terminal decline emerging early in measures of overall motor function (timed chair rises and physical component summary score) and late in basic/instrumental ADL limitations.

Fig 1

Trajectories of motor function over 10 years before death (decedents, n=484) and end of follow-up (survivors, n=5710). Estimated mean scores from linear mixed models (walking speed, grip strength, timed chair rises, physical component summary (PCS) score (SF-36)), and estimated probability from logistic regression (basic/instrumental activities of daily living (ADL/IADL) limitations) with generalised estimated equations. Analyses adjusted for age at year 0, sex, ethnicity, marital status, occupational position, vital status, time terms (time and time²), interactions of these covariates with time terms, and health behaviours, body mass index categories and 9 point multimorbidity score at motor function measurement. Higher scores on walking speed, grip strength, and SF-36 PCS score reflect better motor function; contrary is true for timed chair rises and ADL/IADL limitations. Sex specific standardised scores were used; 1 SD corresponded to 26.2 (25.4) cm/s for walking speed, 8.5 (6.2) kg for grip strength, 3.3 (3.6) more seconds for timed chair rises, and 8.0 (10.7) for PCS score in men (women)