Nonlinear 24‐Hour Blood Pressure Dynamics in Cognitive Impairment and Dementia

BACKGROUND: In cognitive impairment and dementia, where biological functions are disrupted, nonlinear dynamics may reflect dysregulation of blood pressure (BP) that might not be captured by linear variability. We investigated whether nonlinear dynamics of 24-hour BP variability are associated with cognitive impairment and dementia. METHODS: We conducted a cross-sectional analysis of 4854 participants from 3 population-based studies. Raw 24-hour ambulatory BP recordings were structured as time series to quantify nonlinear variability using sample entropy, detrended fluctuation analysis, and Poincaré measures. High entropy and Poincaré values with low detrended fluctuation analysis suggest irregular dynamics, whereas the opposite pattern indicates a predictable BP system. Neurological outcomes included Mini-Mental State Examination, mild cognitive impairment (n=212), and dementia (n=111). RESULTS: The mean age was 67.6±7.89 years (61.0% women). Higher 24-hour systolic BP entropy and Poincaré measures were associated with lower Mini-Mental State Examination; adjusted-mean Mini-Mental State Examination estimates ranged from -0.119 (95% CI, -0.184 to -0.053) to -0.035 (95% CI, -0.060 to -0.010). These measures were also associated with higher odds for prevalent mild cognitive impairment (odds ratios [OR] ≥1.41) and dementia (ORs ranged from 1.32 [95% CI, 1.08-1.60] to 2.36 [95% CI, 1.49-3.74]). Lower detrended fluctuation analysis was related to dementia (OR, 1.64 [95% CI, 1.01-2.68]). Sex, antihypertensive medication, and measures of linear variability did not modify the association between nonlinear variability and cognitive outcomes. CONCLUSIONS: Nonlinear 24-hour BP dynamics were associated with cognitive impairment and dementia. Nonlinear patterns of irregular 24-hour variability may represent a form of BP dysregulation relevant to dementia.