A new study reveals that spending prolonged periods sitting down may accelerate brain aging and cognitive decline in older adults, even among those who maintain regular exercise routines. This finding underscores the importance of reducing sedentary time as a distinct health priority alongside physical activity.
Study Findings
Researchers from Vanderbilt University and other institutions tracked 404 older adults over seven years to examine how sedentary behavior relates to brain health. The participants wore wrist-mounted accelerometers to objectively measure their daily activity levels and underwent brain MRI scans and cognitive assessments throughout the study.
The results, published in the journal Alzheimer’s & Dementia in March 2025, show that participants who spent more time being sedentary exhibited:
- Greater thinning in brain regions typically affected by Alzheimer’s disease
- Faster shrinkage of the hippocampus, a brain region critical for memory
- Worse performance on tests of memory, language, and information processing speed
Perhaps most striking was that these negative associations persisted even though 87% of participants met or exceeded the Centers for Disease Control and Prevention’s recommended guidelines of at least 150 minutes of moderate-to-vigorous physical activity per week.
The APOE-ε4 Connection
The study also found that the negative effects of sedentary behavior were especially pronounced in people carrying the APOE-ε4 gene variant, which is a known genetic risk factor for Alzheimer’s disease. For these individuals, the relationship between sitting time and brain changes was particularly strong.
“Results support the importance of reducing sedentary time, particularly among aging adults at genetic risk for AD,” noted the research team led by Dr. Angela Jefferson of Vanderbilt Memory and Alzheimer’s Center.
Independent Risk Factor
“Our findings suggest that mechanisms underlying the negative impacts of greater sedentary behavior may be operating independently of the mechanisms underlying the positive impacts of physical activity,” the researchers explained. “Physical activity does not mitigate all the harmful effects of being sedentary.”
The average participant in the study spent approximately 13 hours per day in sedentary activities, which is consistent with national averages for older adults.
Why It Matters
Alzheimer’s disease and related dementias affect millions of people worldwide, with cases projected to triple by 2050 as the global population ages. While there is currently no cure, researchers are increasingly focusing on modifiable lifestyle factors that might help prevent or delay cognitive decline.
Dr. Marissa Gogniat, the study’s lead author, emphasized that sedentary behavior should be considered as its own health risk factor, separate from the benefits gained through exercise.
What You Can Do
The researchers suggest that healthcare professionals might consider assessing not only a patient’s exercise regimen but also the amount of time they spend sitting throughout the day.
For individuals concerned about brain health, the message is clear: both regular exercise AND reducing sedentary time are important. Some practical approaches might include:
- Taking regular movement breaks when working at a desk
- Standing or walking while talking on the phone
- Setting timers to remind yourself to stand up and move around
- Considering a standing desk for some tasks
- Breaking up TV viewing with short activity sessions
The study represents an important contribution to our understanding of brain health in aging, highlighting that what we don’t do (sitting too much) may be just as important as what we do (exercising regularly).
