Walking Speed, Cognitive Function, and Dementia Risk in the English Longitudinal Study of Ageing

Ruth A. Hackett, PhD; Hilary Davies-Kershaw, PhD; Dorina Cadar, PhD; Martin Orrell, PhD; Andrew Steptoe, DSc, DPhil

Disclosures

J Am Geriatr Soc. 2018;66(9):1670-1675. 

In This Article

Abstract and Introduction

Abstract

Objectives: To determine the relationships between walking speed, cognitive function, and the interaction between changes in these measures and dementia risk.

Design: Longitudinal observational study.

Setting: English Longitudinal Study of Ageing.

Participants: Individuals aged 60 and older (N=3,932).

Measurements: Walking speed and cognition were assessed at Waves 1 (2002–03) and 2 (2004–05) of the English Longitudinal Study of Ageing. New dementia cases were assessed from Wave 3 (2006–07) to Wave 7 (2014–15). The associations were modelled using Cox proportional hazards regression.

Results: Participants with faster baseline walking speeds were at lower risk of developing dementia (hazard ratio (HR)=0.36, 95% confidence interval (CI)=0.22–0.60). Those with a greater decline in walking speed from Wave 1 to 2 were at greater risk of developing dementia (HR=1.23, 95% CI=1.03–1.47). Participants with better baseline cognition (HR=0.42, 95% CI=0.34–0.54) were at lower risk of developing dementia. Those with a greater decline in cognition from Wave 1 to 2 were at greater risk of developing dementia (HR=1.78, 95% CI=1.53–2.06). Change in walking speed and change in cognition did not have an interactive effect on dementia risk (HR=1.01, 95% CI=0.88–1.17).

Conclusion: In this community-dwelling sample of English adults, those with slower walking speeds and a greater decline in speed over time were at greater risk of developing dementia independent of changes in cognition. Further research is required to understand the mechanisms that may drive these associations.

Introduction

In 2015, an estimated 46.8 million people worldwide had dementia.[1] Dementia is a contributor to disability and life years lost in older individuals.[2] There is no cure for dementia, so identifying potential risk factors may reveal opportunities for prevention. One area of interest is whether physical function is related to dementia onset, because declines in physical and cognitive functioning are indicators of aging, and gait disorders increase with age[3] and are associated with incident dementia.[4]

Walking speed is easier to assess than other gait parameters. Slow walking speed is associated with negative outcomes in older individuals.[5–7] Individuals with cognitive impairment and dementia walk more slowly than individuals without these conditions[8] Furthermore, meta-analytical evidence indicates that slow walking speed is a predictor of dementia.[4,9] Change in walking speed in relation to dementia risk has been less well researched than current walking speed. But in 3,663 French adults, those with a steeper decline in walking speed were at greater risk of dementia than those with a slower decline.[10] Similar findings have been reported in Swedish and Japanese samples.[11,12]

Dementia develops slowly and can be preceded by years of decline in cognitive functioning.[13] Cognition and physical function influence one another in a complex manner.[14] There is some evidence that the association between cognition and walking speed is bidirectional,[15] although most studies find that slow walking is a predictor of decline in cognition but not vice versa.[16,17]

The relationship between changes in cognition and walking speed has been assessed in several studies, but the results are equivocal.[18–20] Findings from a sample of 762 participants in the MacArthur Studies of Successful Aging showed that cognition and walking speed declined in tandem over a 7-year period.[18] A limited association was also detected in a Tasmanian sample, in which a decline in executive function (but no other domains) was associated with a decrease in walking speed.[19] An analysis from the Women's Health Initiative Memory Study failed to detect any association.[20]

Overall, it appears that slow walking speed[9] is associated with greater dementia risk, with more-limited evidence that faster decline in walking speed is also relevant.[10–12] The evidence is mixed as to whether changes in cognition are associated with changes in walking speed,[18–20] and these associations have not been examined in relation to dementia risk. To address these questions, we evaluated whether walking speed and change in walking speed were predictive of dementia in a sample of 3,932 English adults. We also evaluated whether changes in cognition and walking speed have an interactive effect on dementia risk.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....