PROGNOSTIC SIGNIFICANCE OF BLOOD PRESSURE FLUCTUATIONS IN THE MORNING AND EVENING FOR CARDIOVASCULAR OUTCOMES

Abstract

Objective: Independent of office blood pressure (BP) levels, home BP is associated with the occurrence of cardiovascular events. Abnormal diurnal variations in BP have been linked to cardiovascular disease (CVD). However, data on diurnal patterns of home BP, the morning and evening BP difference (MEdiff), are scarce. This study looked into the relationship between all MEdiff indices and cardiovascular outcomes. Design and method: The association was assessed using data from the International Database of Home Blood Pressure in Relation to Cardiovascular Outcome (IDHOCO), which comprised 6753 patients from five cohorts. We found 1254 patients who had taken home BP readings every morning and every evening for more than 14 days. The MEdiff over a 13-day period, omitting the first day, for each patient were used to calculate the average (MEdiff_sbp_avg), minimum (MEdiff sbp_min), and maximum (MEdiff_sbp_max) values. MEdiff is defined as morning (6AM-8AM) minus evening BP (8PM-10PM) measures. The prognostic values of these parameters were assessed using Cox proportional hazards models. Factors adjusted in the base model included age, sex, body mass index, total cholesterol, high-density lipoprotein cholesterol, smoking status, prevalence of diabetes, history of cardiovascular disease, and antihypertensive drug treatment. Results: Only MEdiff_min_sbp strongly predicted CVD (183 events; mean follow-up time of 13.4 years), but MEdiff_avg_sbp (hazard ratio: 0.906, 95% CI: 0.087-1.018 per SD), MEdiff_max_sbp (0.949, 0.846-1.064 per SD) did not. Spline regression analysis with thresholds of -17 mmHg and -4 mmHg revealed a U-curve association between MEdiff_min_sbp and the risk of CVD outcomes. Three groups were identified by MEdiff_min_sbp: lower than -17 mmHg (Low, n = 574), between -17 and -4 mmHg (medium, n = 568) and higher than -4 mmHg (high, n = 112). Compared to the low group, the high group had a significantly higher risk of CVD (1.353, 1.052-1.739), in the models with adjustment for the mean of the morning and evening SBP values, and MEdiff_avg_sbp or various BP variability indices. Conclusions: MEdiff_min_sbp was strongly associated with an increased risk of cardiovascular outcomes, suggesting that it could be a useful BP index for describing abnormal BP diurnal variations for CVD risk prediction.