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

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

Results

Participant Characteristics

We compared the characteristics of those who developed dementia (n= 289) with the characteristics of those who did not (n=3,643). Those who developed dementia were significantly older on average, were less wealthy, had poorer cognition and mobility and significantly slower walking speed, and were more likely to have had a stroke or depressive symptoms than those who did not (Table 1).

Baseline Walking Speed as a Predictor of Dementia

Walking speed at Wave 1 was a predictor of development of dementia, with those with faster walker speeds being less likely to develop dementia (HR=0.36, 95% CI=0.22–0.60) during follow-up (Table 2). This association was robust to adjustment for covariates. Cognitive function at baseline was also an independent predictor of development of dementia (HR=0.42, 95% CI=0.33–0.52), with those with better cognitive function being less likely to develop dementia.

Changes in Walking Speed and Cognition as Predictors of Dementia

Walking speed decreased on average from 0.86 to 0.85 m/s between Waves 1 and 2. Change in walking speed was a significant predictor of dementia (HR=1.23, 95% CI=1.03–1.47), with those who had a greater decrease in walking speed from Wave 1 to Wave 2 having a greater risk of developing dementia independent of covariates and walking speed in Wave 1 (Table 3). Change in cognition was also a predictor, with participants with a greater significant decline in cognitive function between Waves 1 and 2 being at greater risk of developing dementia (HR=1.78, 95% CI=1.53–2.06), but the interaction between walking speed and cognitive function was not a significant predictor of dementia (HR=1.01, 95% CI=0.88–1.17).

Sensitivity Analyses

Three sensitivity analyses were conducted. First, we tested whether walking speed at Wave 2 (2004–05) predicted development of dementia. Participants with faster walking speeds were less likely to develop dementia (HR=0.25) between Waves 3 and 7 (2006–2015) (Supplementary Table S1).

Second, we only considered new events from Wave 4 to 7, omitting any that occurred within 2 years of Wave 2. This reduced the number of cases from 289 to 225 (Supplementary Table S2), but walking speed at Wave 1 remained a predictor of dementia (HR=0.33). Similarly, those with poorer cognition at Wave 1 (HR=0.29) and those who had a greater decline in cognitive function between Waves 1 and 2 (HR=1.69) remained more likely to develop dementia. The effect size for changes in walking speed was similar to that in the full analysis, but the association was no longer significant because of the smaller number of cases.

For the final sensitivity analysis, we excluded participants who were diagnosed using the IQCODE and limited the analysis to those with physician diagnoses. This reduced the number of cases from 289 to 240 (Supplementary Table S3). Walking speed remained a predictor of dementia (HR=0.36). The findings for cognition also remained for baseline cognition (HR=0.26) and change in cognitive function (HR=1.83), but similar to the other sensitivity analysis, change in walking speed no longer predicted development of dementia.

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Table 1. Participant Characteristics (2002–04) According to Dementia Status (2006–15)
Characteristic	Dementia, n = 289	No Dementia, n = 3,643	P-Value
Age, n (%)			<.001
60–69	63 (21.8)	2,016 (55.3)
70–79	135 (46.7)	1,248 (34.3)
≥80	91 (31.5)	379 (10.4)
Male, n (%)	110 (38.2)	1,621 (44.5)	.06
Wealth, decile, mean	5.34 ± 0.17	5.85 ± 0.05	.004
Education, n (%)			.70
<Junior high school	125 (43.2)	1,512 (41.5)
High school	99 (34.3)	1,293 (35.5)
University	65 (22.5)	838 (23)
Walking speed, m/s, mean ± SD	0.78 ± 0.02	0.87 ± 0.01	<.001
Cognition, mean ± SD (range −2.97 to 4.02, Z score)	–0.32 ± 0.04	–0.06 ± 0.01	<.001
Mobility impairment, mean ± SD (range 0–10)^a	2.44 ± 0.14	1.95 ± 0.04	.001
Activity of daily living difficulty, mean ± SD (range 0–6)^b	0.41 ± 0.04	0.32 ± 0.01	.05
Coronary heart disease, n (%)	50 (17.4)	532 (14.6)	.16
Stroke, n (%)	22 (7.5)	149 (4.1)	.02
Diabetes, n (%)	25 (8.8)	270 (7.4)	.26
Hypertension, n (%)	132 (45.6)	1,537 (42.2)	.16
Cancer, n (%)	16 (5.6)	189 (5.2)	.67
Center for Epidemiologic Studies Depression Scale score, mean ± SD (range 0–8)	1.83 ± 0.11	1.38 ± 0.03	<.001

All analyses are age-adjusted.
^aDifficulty with ≥1 common arm and leg functions (range 0–10).
^bWhether participants had difficulties with 6 daily activities (range 0–6).
SD = standard deviation.

Table 2. Hazard Ratio of Walking Speed (2002–03) and Dementia Incidence (2006–15)
Factor	Adjusted HR (95% Confidence Interval)	P-Value
Walking speed, m/s	0.36 (0.22–0.60)	<.001
Cognition^a	0.42 (0.33–0.52)	<.001
Sex	1.09 (0.84–1.42)	.48
Age (reference 60–69)
70–79	2.91 (2.14–3.94)	<.001
≥80	6.68 (4.70–9.49)	<.001
Wealth, decile	0.96 (0.92–1.01)	.09
Education (reference <junior high school)
High school	1.01 (0.76–1.33)	.960
University	1.24 (0.87–1.77)	.242
Mobility impairment^b	0.98 (0.92–1.05)	.596
Activity of daily living difficulty	1.03 (0.87–1.21)	.762
Coronary heart disease	1.12 (0.83–1.52)	.446
Stroke	1.26 (0.82–1.93)	.295
Diabetes mellitus	1.11 (0.74–1.65)	.614
Hypertension	1.06 (0.84–1.34)	.626
Cancer	1.03 (0.63–1.70)	.894
Depression	1.06 (0.99–1.13)	.087

^a1-standard deviation increment in cognition associated with adjusted hazard ratio (HR).
^bDifficulty with ≥1 common arm and leg functions (range 0–10).

Table 3. Hazard Ratio of Change in Walking Speed and Cognition (from 2002–03 to 2004–05) and Dementia Incidence (2006–15)
Factor	Adjusted HR (95% Confidence Interval)	P-Value
Change in walking speed, m/s	1.23 (1.03–1.47)	.02
Change in cognition, z score^a	1.78 (1.53–2.06)	< .001
Walking by cognition interaction	1.01 (0.88–1.17)	.88
Baseline walking speed, m/s^b	0.28 (0.14–0.57)	< .001
Baseline cognition^b	0.27 (0.21–0.35)	< .001
Female	1.19 (0.89–1.56)	.23
Age (reference 60–69)
70–79	3.03 (2.17–4.22)	< .001
≥80	6.59 (4.49–9.68)	< .001
Wealth (decile)	0.97 (0.92–1.02)	.28
Education (reference <junior high school)
High school	0.96 (0.71–1.31)	.80
University	1.44 (0.97–2.13)	.07
Mobility impairment^c	0.99 (0.92–1.06)	.68
Activity of daily living difficulty	0.99 (0.82–1.20)	.90
Coronary heart disease	1.21 (0.87–1.67)	.26
Stroke	1.04 (0.63–1.70)	.88
Diabetes mellitus	1.18 (0.77–1.81)	.45
Hypertension	0.96 (0.75–1.24)	.77
Cancer	1.08 (0.62–1.90)	.79
Depression	1.03 (0.96–1.10)	.48

^a1-standard deviation increment in cognition associated with adjusted hazard ratio (HR).
^b1-m/s increment in walking speed associated with adjusted HR.
^cDifficulty with ≥1 common arm and leg functions (range 0–10).

Supplementary Table 1. Cox proportional hazards regression of the incidence of dementia from waves 3–7 (2006-2015) on walking speed at wave 2 (2004-2005)
	Adjusted HR (95% C.I.)	p value
Walking speed (m/s)*	0.25 (0.13 – 0.47)	< 0.001
Cognitive function†	0.42 (0.34 – 0.54)	< 0.001
Sex¹	1.09 (0.83 – 1.45)	= 0.516
Age 60–69 years 70-79 ≥80	1 2.92 (2.11 – 4.07) 7.26 (4.97 – 10.61)	< 0.001 < 0.001
Wealth (decile) ²	0.97 (0.93 – 1.03)	= 0.383
Education: Lower³ Intermediate Higher	1 0.86 (0.64 – 1.17) 1.17 (0.80 – 1.72)	= 0.346 = 0.417
Mobility impairments⁴ ADL⁵	0.97 (0.91 – 1.05) 1.01 (0.84 – 1.22)	= 0.491 = 0.896
CHD⁶	1.19 (0.86 – 1.65)	= 0.281
Stroke⁶	1.14 (0.69 – 1.86)	= 0.608
Diabetes⁶	1.17 (0.77 – 1.77)	= 0.472
Hypertension⁶	0.95 (0.74 – 1.23)	= 0.688
Cancer⁶	1.16 (0.66 – 2.04)	= 0.602
Depression	1.06 (0.99 – 1.14)	= 0.105

ADL= Activities of daily living; CHD= Coronary Heart Disease; HR= Hazard Ratio
*1 m/s increment in walking speed associated with adjusted HR
†1 SD increment in cognition associated with adjusted HR Note:
¹ Male is the reference group;
²A higher number represents greater wealth
³ Lower = no qualifications; intermediate = junior high & high school; higher = university
⁴ Whether participants had difficulties with ≥1 common arm & leg functions (range 0–10)
⁵ Whether participants had difficulties with 6 daily activities (range 0–6)
⁶No illness is the reference group

Supplementary Table 2. Cox proportional hazards regression of the incidence of dementia from waves 4–7 (2008-2015) on walking speed & cognitive function between waves 1 and 2 (2002-2005)
	Adjusted HR (95% C.I.)	p value
Change in walking speed (m/s)	1.20 (0.98 – 1.45)	= 0.068
Change in cognition (z score)	1.69 (1.42 – 2.01)	< 0.001
Walking by cognition interaction	1.04 (0.86 – 1.22)	= 0.689
Walking speed wave 1 (m/s)*	0.33 (0.15 – 0.73)	= 0.007
Cognition function wave 1†	0.29 (0.22 – 0.39)	< 0.001
Sex¹	1.14 (0.84 – 1.55)	= 0.415
Age 60–69 years 70-79 ≥80	1 3.00 (2.10 – 4.29) 6.89 (4.52 – 10.51)	< 0.001 < 0.001
Wealth (decile) ²	0.97 (0.91 – 1.03)	= 0.258
Education: Lower³ Intermediate Higher	1 1.01 (0.72 – 1.41) 1.45 (0.94 – 2.24)	= 0.976 = 0.096
Mobility impairments⁴ ADL⁵	0.99 (0.92 – 1.08) 1.01 (0.81 – 1.26)	= 0.918 = 0.933
CHD⁶	1.23 (0.85 – 1.78)	= 0.275
Stroke⁶	0.96 (0.54 – 1.72)	= 0.907
Diabetes⁶	1.20 (0.74 – 1.95)	= 0.450
Hypertension⁶	0.94 (0.71 – 1.25)	= 0.670
Cancer⁶	0.82 (0.40 – 1.68)	= 0.594
Depression	1.05 (0.96 – 1.13)	= 0.267

Supplementary Table 3. Cox proportional hazards regression of the incidence of doctor diagnosed dementia from waves 3–7 (2006-2015) on change in walking speed & cognitive function between waves 1 and 2 (2002-2005)
	Adjusted HR (95% C.I.)	p value
Change in walking speed (m/s)	1.17 (0.97 – 1.42)	= 0.102
Change in cognition (z score)	1.83 (1.55 – 2.16)	< 0.001
Walking by cognition interaction	1.03 (0.88 – 1.21)	= 0.708
Walking speed wave 1 (m/s)*	0.36 (0.16 – 0.79)	= 0.012
Cognition function wave 1†	0.26 (0.19 – 0.34)	< 0.001
Sex¹	1.27 (0.94 – 1.74)	= 0.120
Age 60–69 years 70-79 ≥80	1 3.13 (2.17 – 4.51) 7.21 (4.72 – 10.99)	< 0.001 < 0.001
Wealth (decile)²	0.97 (0.92 – 1.03)	= 0.342
Education: Lower³ Intermediate Higher	1 0.88 (0.62 – 1.24) 1.43 (0.93 – 2.20)	= 0.463 = 0.100
Mobility impairments⁴ ADL⁵	0.99 (0.92 – 1.08) 0.93 (0.74 – 1.17)	= 0.906 = 0.535
CHD⁶	1.18 (0.82 – 1.69)	= 0.381
Stroke⁶	0.97 (0.55 – 1.74)	= 0.940
Diabetes⁶	1.19 (0.73 – 1.94)	= 0.490
Hypertension⁶	0.90 (0.68 – 1.20)	= 0.477
Cancer⁶	1.09 (0.59 – 2.02)	= 0.777
Depression	1.02 (0.94 – 1.10)	= 0.693

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

Results

Participant Characteristics

Baseline Walking Speed as a Predictor of Dementia

Changes in Walking Speed and Cognition as Predictors of Dementia

Sensitivity Analyses

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

Results

Participant Characteristics

Baseline Walking Speed as a Predictor of Dementia

Changes in Walking Speed and Cognition as Predictors of Dementia

Sensitivity Analyses

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