Sedentary Time Tied to Brain Volume, Worse Cognition in Older Adults

More time spent sitting or lying down was linked with
neurodegeneration and worse cognitive scores in older adults, even among
people who were physically active, a 7-year study showed.

In cross-sectional models, greater sedentary time was tied to a smaller Alzheimer’s disease-imaging MRI signature (β = -0.0001, P=0.01) and worse episodic memory scores (β = -0.001, P=0.003),
reported Angela Jefferson, PhD, of Vanderbilt University Medical Center
in Nashville, and colleagues. Cross-sectional outcomes varied by APOE4 status.

In longitudinal analyses, more sedentary time was associated with faster hippocampal volume shrinkage (β = -0.1, P=0.008), and declines in naming scores (β = -0.001, P=0.03) and processing speed scores (β = -0.003, P=0.02; β = 0.01, P=0.01), Jefferson and colleagues said in Alzheimer’s & Dementiaopens in a new tab or window.

Longitudinal relationships between sedentary time and hippocampal
volume remained significant when adjusting for moderate-to-vigorous
physical activity (P=0.008), the researchers observed.
Longitudinal associations between sedentary time and cognitive scores
also remained significant when adjusting for moderate-to-vigorous
activity (P<0.03).

“Greater sedentary behavior was associated with smaller hippocampal
volume and worse cognitive performance over a 7-year period despite
taking into account the level of daily moderate-to-vigorous physical
activity each person engaged in,” noted co-author Marissa Gogniat, PhD,
of the University of Pittsburgh.

“These findings suggest that above and beyond physical activity
level, more sedentary behavior is still worse for brain health and
cognition over time,” Gogniat told MedPage Today.

Many associations linking greater sedentary time with brain health and cognitive outcomes were present in APOE4
carriers but not in non-carriers, suggesting increased sedentary time
may be especially harmful for people at increased genetic risk for
Alzheimer’s disease, she added.

Earlier
research from the U.K. Biobank showed that a high level of sedentary
behavior among people ages 60 and older was associated with a higher risk of dementiaopens in a new tab or window. Currently, the U.S. POINTER trialopens in a new tab or window
is looking at whether simultaneously targeting multiple lifestyle
factors in sedentary older adults can reduce cognitive impairment.

Jefferson and colleagues studied 404 participants from the legacy and expansion cohorts of the Vanderbilt Memory and Aging Projectopens in a new tab or window,
a longitudinal study of older adults without dementia at study entry.
Mean baseline age was 71 years; 54% were men and 85% were white.
One-third of participants carried at least one APOE4 allele.

The study incorporated actigraphy, neuroimaging, and
neuropsychological data collected from participants at multiple
intervals. Participants were asked to wear a triaxial accelerometer on
their non-dominant wrist 24 hours a day for 10 consecutive days. The
researchers calculated average minutes per day spent in sedentary
behavior, light physical activity, and moderate-to-vigorous activity for
each participant. Sleep time was excluded.

Participants
had brain MRI at each timepoint. An Alzheimer’s signature was
calculated at baseline and at each follow-up, based on measurements from
regions of interest previously identified as susceptible to Alzheimer’s
neurodegeneration.

At each timepoint, participants also completed a comprehensive
neuropsychological protocol that included information processing speed,
language, executive function, visuospatial ability, and episodic memory
tests.

The average follow-up time was 4.7 years. Over the course of the
study, 27 participants with data for at least two timepoints converted
to dementia.

The average amount of moderate-to-vigorous physical activity time in
the cohort was 61 minutes/day. Most participants met the CDC guidelines
of at least 150 minutes/week of moderate-to-vigorous physical activity.
Moderate-to-vigorous activity was strongly and inversely tied to
sedentary behavior (r = -0.65, P<0.0001), and average sedentary time was 807 minutes/day (13.45 hours).

The cohort lacked racial and ethnic diversity and was well educated, Jefferson and co-authors acknowledged.

“In
addition, our sample was quite active while wearing the actigraphy
devices with 87% of participants meeting the CDC recommendation of at
least 150 minutes of moderate-to-vigorous physical activity per week,”
they noted.

“While such an active sample may limit generalizability, it provides
strong evidence that even among a physically active cohort, such
increased activity is not protective from the impact of greater
sedentary behavior and brain health, especially among APOE4 carriers.”