Association of Neurocognitive and Physical Function With Gait Speed in Midlife

Abstract

Importance: Gait speed is a well-known indicator of risk of functional decline and mortality in older adults, but little is known about the factors associated with gait speed earlier in life.

Objectives: To test the hypothesis that slow gait speed reflects accelerated biological aging at midlife, as well as poor neurocognitive functioning in childhood and cognitive decline from childhood to midlife.

Design, setting, and participants: This cohort study uses data from the Dunedin Multidisciplinary Health and Development Study, a population-based study of a representative 1972 to 1973 birth cohort in New Zealand that observed participants to age 45 years (until April 2019). Data analysis was performed from April to June 2019.

Exposures: Childhood neurocognitive functions and accelerated aging, brain structure, and concurrent physical and cognitive functions in adulthood.

Main outcomes and measures: Gait speed at age 45 years, measured under 3 walking conditions: usual, dual task, and maximum gait speeds.

Results: Of the 1037 original participants (91% of eligible births; 535 [51.6%] male), 997 were alive at age 45 years, of whom 904 (90.7%) had gait speed measured (455 [50.3%] male; 93% white). The mean (SD) gait speeds were 1.30 (0.17) m/s for usual gait, 1.16 (0.23) m/s for dual task gait, and 1.99 (0.29) m/s for maximum gait. Adults with more physical limitations (standardized regression coefficient [β], -0.27; 95% CI, -0.34 to -0.21; P < .001), poorer physical functions (ie, weak grip strength [β, 0.36; 95% CI, 0.25 to 0.46], poor balance [β, 0.28; 95% CI, 0.21 to 0.34], poor visual-motor coordination [β, 0.24; 95% CI, 0.17 to 0.30], and poor performance on the chair-stand [β, 0.34; 95% CI, 0.27 to 0.40] or 2-minute step tests [β, 0.33; 95% CI, 0.27 to 0.39]; all P < .001), accelerated biological aging across multiple organ systems (β, -0.33; 95% CI, -0.40 to -0.27; P < .001), older facial appearance (β, -0.25; 95% CI, -0.31 to -0.18; P < .001), smaller brain volume (β, 0.15; 95% CI, 0.06 to 0.23; P < .001), more cortical thinning (β, 0.09; 95% CI, 0.02 to 0.16; P = .01), smaller cortical surface area (β, 0.13; 95% CI, 0.04 to 0.21; P = .003), and more white matter hyperintensities (β, -0.09; 95% CI, -0.15 to -0.02; P = .01) had slower gait speed. Participants with lower IQ in midlife (β, 0.38; 95% CI, 0.32 to 0.44; P < .001) and participants who exhibited cognitive decline from childhood to adulthood (β, 0.10; 95% CI, 0.04 to 0.17; P < .001) had slower gait at age 45 years. Those with poor neurocognitive functioning as early as age 3 years had slower gait in midlife (β, 0.26; 95% CI, 0.20 to 0.32; P < .001).

Conclusions and relevance: Adults' gait speed is associated with more than geriatric functional status; it is also associated with midlife aging and lifelong brain health.

Figure 1.. Distribution of Gait Speed for Participants in the Dunedin Multidisciplinary Health and Development Study at Age 45 Years

Gait speed distributions for individual walk conditions (usual, dual task, and maximum) are depicted as histograms. Scatterplots illustrate the pairwise correlations between individual walk conditions. The blue lines are linear regression lines.

Figure 2.. Accelerated Aging, Poor Childhood Neurocognitive Function, and Cognitive Decline Associated With Slower Midlife Gait Speed

A-C, The mean pace of aging at age 45 years (years of physiological change per chronological year) (A), mean facial age at age 45 years (z score; mean = 0, SD = 1) (B), and mean brain health at age 3 years (z score; mean = 0, SD = 1) (C) by gait speed quintiles at age 45 years are shown. Generalized additive models are shown in eFigure 2 in the Supplement. D, The childhood-to-adulthood cognitive decline by gait speed quintiles is also shown. Gait speed quintiles are defined as follows: quintile 1, less than 1.32 m/s (181 participants); quintile 2, 1.32 to 1.43 m/s (181 participants); quintile 3, 1.44 to 1.52 m/s (181 participants); quintile 4, 1.53 to 1.63 m/s (181 participants); and quintile 5, greater than 1.63 m/s (180 participants). Error bars indicate standard error.

Figure 3.. Associations Between Brain Structure With IQ and With Gait Speed at Age 45 Years

Brain structure parameters shown include total brain volume (A), mean cortical thickness (B), total surface area (C), and log-transformed white matter hyperintensities (D). The left-hand scatterplots show associations between brain structure parameters and IQ at age 45 years. The right-hand scatterplots show associations between brain structure parameters and composite gait speed at age 45 years. β values represent standardized regression coefficients with 95% CIs adjusted for sex.