. 2022 Apr 20;44(1):17–28. doi: 10.1093/epirev/mxac002

Table 2.

Archetypal Questions Asked and Answered by Observational Studies and Randomized Controlled Trials in the Context of Blood Pressure and Alzheimer Disease or Related Dementias Prevention

Observational Study	RCT
Of people from community X, do those with a SBP of 140 mm Hg at age 50 years have lower dementia risk at age 70 years than those with a SBP of 120 mm Hg at age 50 years, conditional on sociodemographic characteristics, health, and health behaviors at age 50 years?	In persons we can recruit at our clinics, who are at high risk of cardiovascular disease, who are likely to adhere to the study protocol, and have a SBP >160 mm Hg despite available of clinical care and current standards of care, does being randomly assigned to receive Y dose of drug Z for up to 2 years reduce dementia risk compared with being randomly assigned to receive placebo for up to 2 years?

Observational Study

RCT

Of people from community X, do those with a SBP of 140 mm Hg at age 50 years have lower dementia risk at age 70 years than those with a SBP of 120 mm Hg at age 50 years, conditional on sociodemographic characteristics, health, and health behaviors at age 50 years?

In persons we can recruit at our clinics, who are at high risk of cardiovascular disease, who are likely to adhere to the study protocol, and have a SBP >160 mm Hg despite available of clinical care and current standards of care, does being randomly assigned to receive Y dose of drug Z for up to 2 years reduce dementia risk compared with being randomly assigned to receive placebo for up to 2 years?

Abbreviations: ADRD, Alzheimer disease and related dementias; RCT, randomized controlled trial; SBP, systolic blood pressure.