Table 3.

Risk Estimates According to Quintiles of Digit Symbol Substitution Test (DSST) Score Stratified According to Gait Speed

	Gait Speed, m/s
	≥1.0				<1.0
DSST Score Quintile	Included (n=1,179)	Events n	Events per 1,000 Person-Years	Hazard Ratio* (95% CI)	Included (n=1,950)	Events n	Events per 1,000 Person-Years	Hazard Ratio* (95% CI)
Mortality
1 (<27)	80	23	42.8	1.48 (0.88–2.48)	264	103	61.2	2.13 (1.00–4.51)
2 (27–35)	177	43	35.9	1.54 (1.00–2.30)	419	144	54.4	1.75 (1.00–3.17)
3 (36–41)	225	48	31.2	1.04 (0.67–1.60)	425	98	33.0	1.38 (0.82–2.33)
4 (42–50)	299	47	21.7	0.95 (0.62–1.46)	468	89	27.1	1.13 (0.67–1.90)
5 (>50)	398	48	16.3	1.00	374	56	20.8	1.00
Incident disability
1 (<27)	80	29	57.9	1.55 (0.84–2.84)	264	120	82.0	2.51 (1.65–3.80)
2 (27–35)	177	53	47.9	1.45 (0.91–2.31)	419	175	73.6	2.08 (1.46–2.97)
3 (36–41)	225	59	41.3	1.24 (0.82–1.86)	425	162	60.8	1.70 (1.22–2.37)
4 (42–50)	299	86	43.0	1.11 (0.77–1.60)	468	186	63.3	1.65 (1.20–2.27)
5 (>50)	398	99	36.0	1.00	374	115	47.9	1.00

Note: Follow-up time from 1992 to 2002. Event rates and point estimates are shown after stratification for gait speed ≥1.0 m/s. The first quintile of DSST (worst performance) was used as the reference group.

^*Adjusted for age, sex, race, education, gait speed, subclinical disease, congestive heart failure, hypertension, diabetes mellitus, myocardial infarction, physical activity, Modified Mini-Mental State Examination score, presence of at least one subclinical brain infarct, ventricular enlargement ≥Grade 4, and white matter hyperintensities ≥Grade 3.

CI = confidence interval.