About 36 million people worldwide have a form of dementia such as Alzheimer’s disease. If survival, prevention, or treatment do not improve dramatically, this number could double over the next 20 years.1 In the search for interventions to delay or prevent this condition, vascular risk factors have attracted attention. Various studies have shown an association between mid-life hypertension (especially if untreated) and the likelihood of developing dementia,2 3 raising the possibility that antihypertensives might offer an effective form of prevention.

In the linked study (doi:10.1136/bmj.b5465), Li and colleagues report on the possible role of angiotensin receptor blockers in reducing the risk of dementia and slowing progression.4

Several prospective cohort studies show an association between pharmacotherapy for hypertension and a lower risk of cognitive decline or incident dementia (in people under 75 years).3 5 Patients with Alzheimer’s disease treated with antihypertensives seem to have better cognitive outcomes.6 With a few exceptions,5 these observational studies assessed only baseline drug exposure and did not examine the duration of treatment or changes over time. Other concerns include limited study duration, selective loss to follow-up, and confounding by indication. In addition, failure to have a long enough …