I've had an impaired gait for 18 years now and will have until the day I die, but that has absolutely nothing to do with my cognitive health, which is working great.
The time course of motor and cognitive decline in older adults and their associations with brain pathologies: a multicohort study
Summary
Background
Many
studies have reported that impaired gait precedes cognitive impairment
in older people. We aimed to characterise the time course of cognitive
and motor decline in older individuals and the association of these
declines with the pathologies of Alzheimer's disease and related
dementias.
Methods
This
multicohort study used data from three community-based cohort studies
(Religious Orders Study, Rush Memory and Aging Project, and Minority
Aging Research Study, all in the USA). The inclusion criteria for all
three cohorts were no clinical dementia at the time of enrolment and
consent to annual clinical assessments. Eligible participants consented
to post-mortem brain donation and had post-mortem pathological
assessments and three or more repeated annual measures of cognition and
motor functions. Clinical and post-mortem data were analysed using
functional mixed-effects models. Global cognition was based on 19
neuropsychological tests, a hand strength score was based on grip and
pinch strength, and a gait score was based on the number of steps and
time to walk 8 feet and turn 360°. Brain pathologies of Alzheimer's
disease and related dementias were assessed at autopsy.
Findings
From
1994 to 2022, there were 1570 eligible cohort participants aged 65
years or older, 1303 of whom had cognitive and motor measurements and
were included in the analysis. Mean age at death was 90·3 years (SD
6·3), 905 (69%) participants were female, and 398 (31%) were male.
Median follow-up time was 9 years (IQR 5–11). On average, cognition was
stable from 25 to 15 years before death, when cognition began to
decline. By contrast, gait function and hand strength declined during
the entire study. The combinations of pathologies of Alzheimer's disease
and related dementias associated with cognitive and motor decline and
their onsets of associations varied; only tau tangles, Parkinson's
disease pathology, and macroinfarcts were associated with decline of all
three phenotypes. Tau tangles were significantly associated with
cognitive decline, gait function decline, and hand function decline
(p<0·0001 for each); however, the association with cognitive decline
persisted for more than 11 years before death, but the association with
hand strength only began 3·57 years before death and the association
with gait began 3·49 years before death. By contrast, the association of
macroinfarcts with declining gait function began 9·25 years before
death (p<0·0001) compared with 6·65 years before death (p=0·0005) for
cognitive decline and 2·66 years before death (p=0·024) for decline in
hand strength.
Interpretation
Our
findings suggest that average motor decline in older adults precedes
cognitive decline. Macroinfarcts but not tau tangles are associated with
declining gait function that precedes cognitive decline. This suggests
the need for further studies to test if gait impairment is a clinical
proxy for preclinical vascular cognitive impairment.
Funding
National Institutes of Health.
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