To the Editor.—
The article entitled "Improved Cognition After Control of Risk Factors for Multi-infarct Dementia"1 fails to provide data to support a major conclusion of the study. One hypothesis the authors propose to test is that control of hypertension improves cognition in patients with multi-infarct dementia (MID). The data provided to support this hypothesis involve the division of hypertensive subjects with MID into two groups on the basis of an outcome variable—whether or not improvement in mental function occurred. The single measure shown to be different between groups was the mean systolic blood pressure after treatment, another outcome variable.This central result is only indicative of a correlational relationship at one point in time, with no hope of inferring causation since no antecedent treatment differences between the improved and the unimproved groups were reported. No information on pretreatment blood pressure was provided to allow the effect of treatment
Robinson BE, Keller DM. Multi-infarct Dementia. JAMA. 1987;257(8):1048–1049. doi:10.1001/jama.1987.03390080038015
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