The Prognostic Power of Diastolic-to-Systolic Arterial Stiffening Is Greater at Nighttime in Middle-Age Patients Undergoing 24-Hour Ambulatory Blood Pressure Monitoring

Objective: It has been previously shown that part of the pulse pressure (PP), the systolic-diastolic blood pressure (BP) difference, relates quantitatively to the relative change in arterial stiffness between the diastolic- to the systolic pressure (‘stiffening’). This part so-called ‘stiffening PP component’ (stPP) can be determined from repeated BP measurements. The study objective was to assess and compare the hazard ratio of stPP during daytime and nighttime for outcomes in a large cohort of young and middle-age patients using 24-hour ambulatory BP monitoring (24hABPM). Design and method: The study included analysis of 24hABPM records of adequate quality provided by the Spanish Ambulatory Blood Pressure Registry of patients referred by their physicians at 223 primary care centers in Spain. For SD=standard deviation, and K=SD(SBP)/SD(DBP), stPP=PP 1- ln(K)/(K-1). Hazard ratios (HRs) for each SD change in stPP were determined for the age classes 20-40, 41-50, and 51-60 years, using Cox regression models, adjusted for age, sex, BMI, smoking status, diabetes, dyslipidemia, mean DBP, pulse rate, SD(SBP), antihypertensive treatment, and previous cardiovascular disease (CVD). The endpoints were total mortality, and death from CVD, or coronary heart disease (CHD). Results: Of the 24,260 patients included mean(SD) age 48.0(9.0) years, 34% male 845 deaths occurred during the follow-up period of 9.6(2.2) years. The Table shows that stPP had statistically-significant predictive power for all endpoints at age 51-60 years for both day and night (where day HR was larger or comparable to its night value), but for night only at age 41-50 years. At age 20-40 years stPP lacked predictive power for total mortality and CVD death. For CHD death day stPP suggested increased risk while night stPP suggested protective effect, but both lacked statistical significance probably due to the small number of deaths. Conclusions: The stiffening PP component derived from 24hABPM displayed statistically significant predictive power during nighttime at middle age, in spite of its relatively small mean value.