['This study was designed to explore the appropriate blood pressure (BP) target required to reduce cognitive decline and brain white matter lesions (WMLs) in elderly hypertensive patients.', 'Elderly patients (n = 294, ≥80 years of age) being treated for hypertension were enrolled in a longitudinal study examining cognitive impairment after an initial assessment and a period of 4 years. All patients underwent neurological and cognitive assessment, laboratory examination, and magnetic resonance imaging of the brain.', 'The 4-year follow-up examination revealed that body mass index, alcohol consumption, systolic blood pressure (SBP), diastolic blood pressure, and Mini-Mental State Examination (MMSE) all showed a significant decline, whereas fasting plasma glucose, white matter hyperintensities (WMH) volume, and the WMH/total intracranial volume (TIV) ratio were significantly increased when compared with baseline observations. Interestingly, the decline in MMSE, as well as the increment of WMH and WMH/TIV ratio was smaller in patients with SBP ranging from 140 to 160 mm Hg than in those whose SBP was lower than 140 mm Hg or higher than 160 mm Hg (P < .05). Furthermore, we observed that a 15 to 35 mm Hg targeted lowering of SBP in the elderly patients was more beneficial to our cognitive analysis than treatments that achieved less than 15 mm Hg or greater than 35 mm Hg (P < .05).'] Is excessive lowering of blood pressure beneficial for progression of brain white matter hyperintensive and cognitive impairment in elderly hypertensive patients : 4-year follow-up study?