Known reasons for cholesterol changes can vary among

So, unless the study accounts for these, seems like cholesterol change might just be at best an indirect marker of potential risk to develop dementia.

science

Fluctuating Cholesterol Levels Linked to 60% Higher Dementia Risk

south_korea_ln

It's very hard, indeed. 

Known reasons for cholesterol changes can vary among
- change in exercise/activity routine 
- dietary changes 
- stress/sleep habits
- alcohol consumption 
- genetics 
- ....

So, unless the study accounts for these, seems like cholesterol change might just be at best an indirect marker of potential risk to develop dementia.

