The data source for this study was 1686 non-demented adults aged 65–90 years
who underwent baseline examinations conducted during the period from 2002
through 2014 in the Kusatsu Longitudinal Study. The average number of followup assessments was 3.9, and the total number of observations was 6509. There were
196 (11.6%) cases of incident dementia among the 1686 participants during the
period through 2014. Gait speed was measured over a straight 5-m walkway on a flat
floor. Participants were requested to walk at their usual pace and maximum pace
(m/s). Step length (cm) was measured by two staff members. As part of the Japanese
Long-Term Care Insurance (LTCI) system, which covers most persons with dementia, the Ministry of Health, Labour and Welfare of Japan requires that a physician
provide an observer-based rating for elderly adults with dementia. The categories for
the scale are no dementia, some dementia but almost independent in daily life (level
I), dementia with some difficulty communicating but with independence in daily
living with minimal observation (level II), dementia with some difficulty communicating and a need for partial care (level III), and severe dementia with difficulty
communicating and a need for complete care (level IV). In this study, disabling
dementia was defined as level II dementia or worse, as this is the level at which
applicants are entitled to receive insurance benefits, including institutional, home,
respite, and/or day care and loans of equipment. Among men, mean (SD) age was
70.9 (5.2) years, 44.6% had no chronic diseases, and the average number of years of
education was 10.5 (2.9) at baseline. Among women, baseline age was 71.4 (5.8)
years, 43.3% had no chronic diseases, and average number of years of education was
9.5 (2.5).
Three trajectory patterns—high, middle, and low—were identified for gait speed
and step length at usual and maximum paces in men and women (Fig. 2). The
average posterior probability of allocating each participant into the three groups was
0.82–0.90, indicating a good fit of the model of group trajectories to individual
trajectories. When compared to participants in the high trajectory group during
follow-up, those in the middle and low trajectory groups for usual gait speed had
HRs of 1.70 (95% CI, 0.96–3.07) and 3.46 (1.88–6.40), respectively, for incident
disabling dementia after controlling for important confounders. Participants in the
middle and low trajectory groups for usual step length had HRs of 1.00 (0.62–1.60)
and 2.12 (1.29–3.49), respectively, for incident disabling dementia, when compared
to participants in the high trajectory group. For maximum gait speed, the
corresponding HRs were 1.53 (0.78–2.98) and 2.05 (1.02–3.50). Participants in
the middle and low trajectory groups for maximum step length had HRs of 1.93
(1.06–3.50) and 2.80 (1.48–5.28), respectively.
This prospective study using repeated measures analysis of data from
nondemented community-dwelling older Japanese was the first to show that potential gait speed and step length trajectories are independent predictors of incident
disabling dementia, after adjustment for important confounders. Our findings for
Japanese elders are consistent with those reported for Western populations
(Bohannon & Williams Andrews, 2011) and indicate that gait performance measure
trajectories exhibit age-related linear change in later life. There is growing interest in
the association between gait performance and degenerative brain lesions. Previous
64
Y. Taniguchi and H. Matsushita
who underwent baseline examinations conducted during the period from 2002
through 2014 in the Kusatsu Longitudinal Study. The average number of followup assessments was 3.9, and the total number of observations was 6509. There were
196 (11.6%) cases of incident dementia among the 1686 participants during the
period through 2014. Gait speed was measured over a straight 5-m walkway on a flat
floor. Participants were requested to walk at their usual pace and maximum pace
(m/s). Step length (cm) was measured by two staff members. As part of the Japanese
Long-Term Care Insurance (LTCI) system, which covers most persons with dementia, the Ministry of Health, Labour and Welfare of Japan requires that a physician
provide an observer-based rating for elderly adults with dementia. The categories for
the scale are no dementia, some dementia but almost independent in daily life (level
I), dementia with some difficulty communicating but with independence in daily
living with minimal observation (level II), dementia with some difficulty communicating and a need for partial care (level III), and severe dementia with difficulty
communicating and a need for complete care (level IV). In this study, disabling
dementia was defined as level II dementia or worse, as this is the level at which
applicants are entitled to receive insurance benefits, including institutional, home,
respite, and/or day care and loans of equipment. Among men, mean (SD) age was
70.9 (5.2) years, 44.6% had no chronic diseases, and the average number of years of
education was 10.5 (2.9) at baseline. Among women, baseline age was 71.4 (5.8)
years, 43.3% had no chronic diseases, and average number of years of education was
9.5 (2.5).
Three trajectory patterns—high, middle, and low—were identified for gait speed
and step length at usual and maximum paces in men and women (Fig. 2). The
average posterior probability of allocating each participant into the three groups was
0.82–0.90, indicating a good fit of the model of group trajectories to individual
trajectories. When compared to participants in the high trajectory group during
follow-up, those in the middle and low trajectory groups for usual gait speed had
HRs of 1.70 (95% CI, 0.96–3.07) and 3.46 (1.88–6.40), respectively, for incident
disabling dementia after controlling for important confounders. Participants in the
middle and low trajectory groups for usual step length had HRs of 1.00 (0.62–1.60)
and 2.12 (1.29–3.49), respectively, for incident disabling dementia, when compared
to participants in the high trajectory group. For maximum gait speed, the
corresponding HRs were 1.53 (0.78–2.98) and 2.05 (1.02–3.50). Participants in
the middle and low trajectory groups for maximum step length had HRs of 1.93
(1.06–3.50) and 2.80 (1.48–5.28), respectively.
This prospective study using repeated measures analysis of data from
nondemented community-dwelling older Japanese was the first to show that potential gait speed and step length trajectories are independent predictors of incident
disabling dementia, after adjustment for important confounders. Our findings for
Japanese elders are consistent with those reported for Western populations
(Bohannon & Williams Andrews, 2011) and indicate that gait performance measure
trajectories exhibit age-related linear change in later life. There is growing interest in
the association between gait performance and degenerative brain lesions. Previous
64
Y. Taniguchi and H. Matsushita