Proposal of reference value for day-to-day blood pressure variability based on two outcomes: the Ohasama study

Background: This study aimed to propose reference values for day-to-day home blood pressure (BP) variability that align with the established hypertension threshold of home BP for the risk of two different outcomes: cardiovascular mortality and cognitive decline. Methods: This prospective study was conducted in Ohasama town, Japan, with 1212 participants assessed for cardiovascular mortality risk (age: 64.7 years, 33.6% men). Additionally, 678 participants (age: 62.7 years, 31.1% men) were assessed for cognitive decline risk (Mini-Mental Scale Examination score <24). The within-individual coefficient of variation (CV) of home morning SBP (HSBP) was used as the index of day-to-day BP variability (%). Adjusted Cox regression models were used to estimate the HSBP-CV values, which provided the 10-year outcome risk at an HSBP of 135 mmHg. Results: A total of 114 cardiovascular deaths and 85 events of cognitive decline (mean follow-up:13.9 and 9.6 years, respectively) were identified. HSBP and HSBP-CV were associated with increased risks for both outcomes, with adjusted hazard ratios per 1-standard deviation increase of at least 1.25 for cardiovascular mortality and at least 1.30 for cognitive decline, respectively. The adjusted 10-year risks for cardiovascular mortality and cognitive decline were 1.67 and 8.83%, respectively, for an HSBP of 135 mmHg. These risk values were observed when the HSBP-CV was 8.44% and 8.53%, respectively. Conclusion: The HSBP-CV values indicating the 10-year risk of cardiovascular mortality or cognitive decline at an HSBP of 135 mmHg were consistent, at approximately 8.5%. This reference value will be useful for risk stratification in clinical practice.