No strategy has been found to reliably prevent cognitive impairment or dementia.  In the Heart Outcomes Prevention Evaluation-3 (HOPE 3) presented at the American Heart Association Scientific Sessions 2016, researchers evaluated whether long-term cholesterol lowering or blood pressure-lowering delayed cognitive decline in individuals at moderate risk for cardiovascular disease. 

12,705 participants were randomized to receive either blood pressure medication (candesartan /hydrochlorothiazide) or placebo and a cholesterol-lowering statin (rosuvastatin) or placebo. 1,626 study participants also completed cognitive and functional outcome questionnaires at baseline and study end almost six years later.

Participants came from 221 centers in 21 countries and were on average 74 years old and 59 percent were women.

Participants in each group did demonstrate cognitive decline, but there was no difference in the decline between those in the active or control groups for the blood pressure lowering arm or the cholesterol lowering arm or the combination. Neither treatment demonstrated any adverse effect on cognition.

Five and half years of blood pressure lowering and cholesterol lowering in an intermediate risk population did not prevent cognitive decline. It is not clear if early initiation and longer term treatment may have benefit.