Day-to-day blood pressure variability in older persons - optimizing measurement.

Background: Higher blood pressure variability (BPV) is associated with adverse clinical outcomes but lack of standardized methodology hampers clinical translation. Day-to-day BPV seems most promising for an older population, especially those with cognitive impairment. This study aimed to determine the optimal number of measurements for obtaining day-to-day BPV in this population.

Methods: We included 127 patients attending the geriatric outpatient memory clinic, who measured blood pressure for seven days, morning and evening. Blood pressure measurements of day one were discarded and the coefficient of variation was calculated to assess BPV. Concordance between 7-day BPV (CV 7days ) and a reduced number of measurement days (CV 6days - CV 3days ) was analysed with Bland-Altman plots, intraclass correlation coefficient (ICC), and an a priori determined threshold of a 95% confidence interval (CI) with a lower bound of 0.75.

Results: The mean age was 74.6 ± 8.6 years, 49% were female, and had dementia or mild cognitive impairment in 37% and 33% respectively. Reducing the number of measurement days resulted in wider limits of agreement. Concordance decreased when reducing measurement days and reached our predefined threshold with four measurement days (ICC = 0.91, 95% CI = 0.87 - 0.93). BPV derived from five measurement days showed a similar relationship with diagnosis as our reference BPV value obtained with seven days.

Conclusion: Our results suggest that systolic home blood pressure should be measured in the morning and evening for at least five consecutive days in duplicate to obtain reliable day-to-day BPV values in older adults with cognitive complaints.