> Findings: In this retrospective study of prospectively collected data of 49 841 adults participating in the UK Biobank, more time spent in sedentary behaviors (determined through a machine learning–based analysis of wrist-worn accelerometer data) was significantly associated with higher risk of incident dementia.

I don't think this comes as a big surprise to anyone, but nice to have a large study reinforcing it.

Alternate explanation: dementia leads to depression, which leads to sedentary behavior. Not sure how we would disentangle cause and effect here.