Many believe that performing daily workouts is sufficient enough to protect the brain from dangers of leading a sedentary lifestyle. However, contemporary studies suggest that even those people who do regular exercises can be affected negatively by spending time sitting.
During a 7-year study, 404 adults aged 50 years and older who participated in the Vanderbilt Memory and Ageing Project were followed by researchers. Participants were wearing devices measuring their sedentary time and physical activity level.
They also passed repeated MRI scans and cognitive assessments for the brain examination. The study results showed that those participants who spent more time sitting had a greater decrease in brain volume as compared to those who spent less time sitting. Thus, it was shown that the more time people were sitting, the more decline showed in their cognitive abilities.
It should also be noted that the study proved that the associations remained even after including the results of moderate physical activities. This means that performing different exercises cannot totally reduce the negative effect of prolonged sitting.
However, it did not prove that prolonged sitting causes brain shrinkage or Alzheimer's disease because it was observational. The study showed an association between sedentary behaviour and brain health changes but did not establish proof of any cause-and-effect relationship.
Reference:
Gogniat, M. A., et al. (2025). Increased sedentary behavior is associated with neurodegeneration and worse cognition in older adults over a 7-year period despite high levels of physical activity. Alzheimer’s & Dementia, 21(5), e70157. https://doi.org/10.1002/alz.70157
More About the Research
Why is sitting getting so much attention?
Most of us know that regular exercise is good for our health. But there is another part of the picture that is easy to overlook: how much time we spend sitting during the rest of the day.
You might go for a walk in the morning, exercise at the gym, or play a sport, and then spend several hours sitting at a desk, watching television or using a computer.
Researchers are becoming increasingly interested in whether those long periods of inactivity matter independently of how much exercise someone does.
The 2025 study by Marissa Gogniat and colleagues provides an interesting example. The researchers followed 404 adults aged 50 and older who were part of the Vanderbilt Memory and Aging Project. Participants wore activity-monitoring devices, underwent brain MRI scans and completed cognitive assessments over a period of seven years.
What did the researchers find?
The researchers found that people who spent more time being sedentary had associations with poorer brain and cognitive outcomes.
In the longitudinal analysis, greater sedentary time was associated with faster reductions in hippocampal volume. The hippocampus is a brain region that plays an important role in memory.
Greater sedentary time was also associated with declines in certain measures of cognition, including naming ability and processing speed.
Interestingly, these associations were examined while taking physical activity into account. This suggests that simply meeting exercise targets may not completely remove the association seen between prolonged sedentary time and the brain measures studied.
That doesn't mean exercise isn't valuable. Rather, the research raises the possibility that both regular physical activity and reducing excessive sedentary time may matter for healthy ageing.
Does this mean sitting causes brain shrinkage?
This is where we need to be careful.
The study found an association between sedentary behaviour and changes in brain structure and cognition. It did not prove that sitting causes brain shrinkage, Alzheimer's disease or dementia.
There could be other factors involved. For example, health conditions, lifestyle factors and other characteristics may influence both how much time someone spends sitting and their brain health.
The researchers used statistical adjustments to account for a number of factors, but an observational study cannot establish cause and effect in the same way that a well-designed randomised intervention trial can.
So the headline shouldn't be “sitting causes Alzheimer's.” The evidence doesn't establish that.
What about people who exercise regularly?
This is probably the most interesting question.
Exercise has many well-established health benefits, and physical activity is considered an important part of healthy ageing. The findings from this study shouldn't be interpreted as suggesting that exercise is pointless.
Instead, they add another possibility: being physically active and spending less time sitting may both be relevant to brain health.
The researchers themselves noted that physical activity may lessen some of the detrimental associations of sedentary behaviour, but did not completely eliminate them.
In other words, going for a workout doesn't necessarily mean that the rest of the day can be spent sitting without any other consideration.
What does other research say?
The 2025 study isn't the only research looking at this question.
A systematic review published in Frontiers in Ageing Neuroscience in 2025 examined 33 studies investigating sedentary behaviour, cognition and brain health in older adults. Overall, the review found that greater sedentary behaviour was associated with poorer cognition and brain health, although the strength of the associations varied between studies and depended partly on how sedentary behaviour was measured and classified.
That variation is important. Research in this area is still developing, and studies don't all measure sedentary behaviour or cognitive health in exactly the same way.
What can we take from this?
The safest takeaway isn't that sitting is going to cause Alzheimer's disease.
Instead, this research gives us another reason to think about how we spend the whole day, rather than focusing only on the time we spend exercising.
A person could have a regular exercise routine but still spend many hours sitting at work, travelling, watching television or using a computer.
Breaking up long periods of sitting with movement is therefore an interesting area of research, particularly as people get older.
More research is needed to understand exactly how sedentary behaviour might affect the ageing brain and whether reducing sitting time directly changes the risk of cognitive decline.
For now, though, the message is quite simple: exercise is important, but moving regularly throughout the day may be important too.
Rather than thinking of exercise and sitting as an either-or situation, perhaps it makes more sense to think about both.
References
Gogniat, M. A., Khan, O. A., Li, J., et al. (2025). Increased sedentary behavior is associated with neurodegeneration and worse cognition in older adults over a 7-year period despite high levels of physical activity. Alzheimer's & Dementia, 21(5), e70157. https://pubmed.ncbi.nlm.nih.gov/40357887/
Gogniat, M. A., Won, J., Cruz, C., et al. (2025). Sedentary behavior, cognition, and brain health in older adults: a systematic review. Frontiers in Aging Neuroscience, 17, 1622049. https://pubmed.ncbi.nlm.nih.gov/40697359/
Gogniat, M. A., Khan, O. A., Li, J., et al. (2025). Increased sedentary behavior is associated with neurodegeneration and worse cognition in older adults over a 7-year period despite high levels of physical activity. Alzheimer's & Dementia, 21(5), e70157. https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.70157
