Previous studies have shown that heart health at 50 predicts brain health at 75.

This study is interesting in that it quantifies the benefit as 12.5 extra dementia-free years. People with 0 risk factors had 30 years of dementia-free survival, vs 17.5 years for people with all 3 risk factors measured.

The risk factors in this specific study are blood pressure, diabetes (HbA1c), and smoking. You could reasonably also include cholesterol/ApoB, inflammation (hs-CRP), and perhaps Lp(a) as potential risk factors.