The medial temporal lobe (MTL) includes the hippocampus, and is essential to the processing and storage of long-term memories. Recent research demonstrates that in people over 45, the number of hours spent sitting per day is inversely related to the thickness of the MTL. Crudely put, too many hours sitting can reduce your ability to remember. Since it is already known that sedentary behavior is linked to an increased risk of heart disease, diabetes and premature death in middle-age and older adults, this most recent work adds another disturbing element to the argument against sitting too much.
While the research appears to show that physical activity, even at high levels, is insufficient to offset the harmful effects of sitting for extended periods, the work is preliminary in that the study focused on hours spent sitting, and did not take into consideration whether participants took breaks during long stretches of sedentary behavior. The researchers said that this could be a limitation of their results.
Here are links to two media articles on the work:
Sitting Too Much Can Change Your Brain & Impact Your Memory, A New Study Says
Too Much Sitting May Shrink the Part of Your Brain Tied to Memory
Here is a link to the research article:
Sedentary behavior associated with reduced medial temporal lobe thickness in middle-aged and older adults