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A neuroimaging study of older adults found that those who spent more time sitting tended to have worse episodic memory. They also showed faster reductions in hippocampal volume over the 7-year study period and experienced more rapid declines in cognitive processing speed. The findings were published in the Journal of the Alzheimer’s Association.
Sedentary behavior refers to activities that involve sitting or lying down and require very low energy expenditure, such as watching TV, working at a desk, or using a computer. It is distinct from simply being physically inactive; a person can meet daily exercise recommendations and still spend much of the day in a sedentary state.
Prolonged sedentary behavior is associated with a range of negative health outcomes, including increased risks of heart disease, obesity, type 2 diabetes, and certain cancers. It has also been linked to poor posture, back pain, reduced muscle strength, and higher levels of anxiety and depression.
Study author Marissa A. Gogniat and her colleagues set out to examine the relationship between sedentary time and structural brain changes in older adults who did not have dementia at the start of the study. They hypothesized that, after adjusting for daily physical activity, higher levels of sedentary behavior at baseline would be associated with greater neurodegeneration—especially in brain regions vulnerable to Alzheimer’s disease, such as the temporal and parietal lobes. They also expected more sedentary time to be linked with worse cognitive performance, particularly in memory and language, which are commonly affected in Alzheimer’s disease.
Participants were drawn from the Legacy and Expansion Cohorts of the Vanderbilt Memory and Aging Project, a longitudinal observational study of older adults without dementia at baseline.
The sample included 404 individuals with an average age of 71. About 54% were male. Of these, 244 participants completed at least one follow-up assessment over the course of the study, while 160 had data collected at only a single time point.
Each participant wore a triaxial accelerometer on their non-dominant wrist for 10 consecutive days, 24 hours a day. These devices measured movement and allowed researchers to quantify sedentary time, as well as levels of light and moderate-to-vigorous physical activity.
Participants also underwent brain imaging using magnetic resonance imaging (MRI), completed comprehensive neuropsychological assessments, and provided blood samples that were used to determine whether they carried the APOE ε4 allele—a well-established genetic risk factor for Alzheimer’s disease.
The cognitive assessments evaluated episodic memory, language, processing speed, executive function, and visuospatial ability.
Cross-sectional findings showed that individuals who spent more time sitting had smaller volumes in brain regions commonly affected by Alzheimer’s disease. This included lower total gray matter volume and reduced volumes in the frontal and parietal lobes. These individuals also tended to perform worse on tests of episodic memory.
When the researchers analyzed changes over time, they found that higher sedentary time at baseline predicted a faster decline in hippocampal volume—a key brain structure involved in memory. In addition, participants with greater sedentary time experienced more rapid declines in naming ability and cognitive processing speed. These age-related declines occur naturally, but the study found they progressed more quickly in those who spent more time being sedentary.
“In conclusion, we found that greater sedentary behavior was associated with worse neurodegeneration and cognition cross-sectionally and longitudinally despite high levels of physical activity among the cohort,” the study authors wrote. “Healthcare professionals might consider assessing not only a patient’s exercise regimen but also the amount of time they are sedentary throughout the day, recommending a reduction in such sedentary behavior in addition to increasing daily physical activity.”
The study contributes to the growing body of research linking sedentary behavior with cognitive decline and brain atrophy in older adulthood. However, the observational design does not allow for conclusions about causality. While sedentary behavior may contribute to neurodegeneration, it is also possible that early brain changes associated with cognitive decline lead individuals to spend more time sitting.
The paper, “Increased sedentary behavior is associated with neurodegeneration and worse cognition in older adults over a 7-year period despite high levels of physical activity,” was authored by Marissa A. Gogniat, Omair A. Khan, Judy Li, Chorong Park, W. Hudson Robb, Panpan Zhang, Yunyi Sun, Elizabeth E. Moore, Michelle L. Houston, Kimberly R. Pechman, Niranjana Shashikumar, L. Taylor Davis, Dandan Liu, Bennett A. Landman, Keith R. Cole, Corey J. Bolton, Katherine A. Gifford, Timothy J. Hohman, Kelsie Full, and Angela L. Jefferson.
