The relationship between blood pressure and cognitive function

BACKGROUND: Although an elevated systolic blood pressure (SBP) is associated with cognitive dysfunction, BP may decrease with advanced cognitive dysfunction; therefore, we attempted to identify the turning point in the relationship between cognitive function and SBP in elderly subjects. METHODS: In pooled datasets of general populations and outpatient clinics (age>65 years), in which the risk of frailty or cognitive dysfunction was assessed (N = 4076), the relationship between SBP and the Mini Mental State Examination (MMSE) score was examined. RESULTS: Mean age was 72.5 ± 6.2 years (male 45.1%), and SBP was 133.0 ± 19.5 mmHg. In an analysis of locally weighted scatter plot smoothing, the relationship between SBP and MMSE scores changed at an MMSE score of 24 points. In subjects with preserved cognitive function (MMSE ≥24 points), MMSE scores decreased with increases in SBP (B = −0.047 per 10 mmHg increase, P = 0.002) after adjustments for age, sex, body mass index, alcohol habit, smoking status, diabetes, a history of stroke, and the geriatric nutritional index; however, in subjects with reduced cognitive function (MMSE<24 points), decreases in the MMSE score were associated with reductions in SBP (B = 1.178 per 1 point decrease in the MMSE score, P = 0.002). CONCLUSION: The relationship between SBP and cognitive function changed at a MMSE score of approximately 24 points (mild to moderate cognitive dysfunction). In patients with preserved MMSE, higher BP values were associated with a reduction of cognitive function, but this was not a case for those with impaired MMSE.