Effects of low blood pressure in cognitively impaired elderly patients treated with antihypertensive drugs

IMPORTANCE: The prognostic role of high blood pressure and the aggressiveness of blood pressure lowering in dementia are not well characterized. OBJECTIVE: To assess whether office blood pressure, ambulatory blood pressure monitoring, or the use of antihypertensive drugs (AHDs) predict the progression of cognitive decline in patients with overt dementia and mild cognitive impairment (MCI). DESIGN, SETTING, AND PARTICIPANTS: Cohort study between June 1, 2009, and December 31, 2012, with a median 9-month follow-up of patients with dementia and MCI in 2 outpatient memory clinics. MAIN OUTCOMES AND MEASURES: Cognitive decline, defined as a Mini-Mental State Examination (MMSE) score change between baseline and follow-up. RESULTS: We analyzed 172 patients, with a mean (SD) age of 79 (5) years and a mean (SD) MMSE score of 22.1 (4.4). Among them, 68.0% had dementia, 32.0% had MCI, and 69.8% were being treated with AHDs. Patients in the lowest tertile of daytime systolic blood pressure (SBP) (≤ 128 mm Hg) showed a greater MMSE score change (mean [SD], -2.8 [3.8]) compared with patients in the intermediate tertile (129-144 mm Hg) (mean [SD], -0.7 [2.5]; P = .002) and patients in the highest tertile (≥ 145 mm Hg) (mean [SD], -0.7 [3.7]; P = .003). The association was significant in the dementia and MCI subgroups only among patients treated with AHDs. In a multivariable model that included age, baseline MMSE score, and vascular comorbidity score, the interaction term between low daytime SBP tertile and AHD treatment was independently associated with a greater cognitive decline in both subgroups. The association between office SBP and MMSE score change was weaker. Other ambulatory blood pressure monitoring variables were not associated with MMSE score change. CONCLUSIONS AND RELEVANCE: Low daytime SBP was independently associated with a greater progression of cognitive decline in older patients with dementia and MCI among those treated with AHDs. Excessive SBP lowering may be harmful for older patients with cognitive impairment. Ambulatory blood pressure monitoring can be useful to help avoid high blood pressure overtreatment in this population.