ASSOCIATION BETWEEN ISOLATED LOW OR HIGH DIASTOLIC BLOOD PRESSURE WITH ALL-CAUSE AND CARDIOVASCULAR MORTALITY: EVIDENCE FROM NHANES (1999–2018)

Objective: The relationship between either high or markedly low diastolic blood pressure (DBP) with normalized systolic blood pressure and the risks of all-cause mortality in hypertensive patients remains unclear. This study aimed to investigate the associations between isolated high DBP (IHDBP) and isolated low DBP (ILDBP) with all-cause and cardiovascular mortality in hypertensive patients.Design and method: The study included 9,915 participants with systolic blood pressure below 130 mmHg and aged over 18 years with hypertension from the US National Health and Nutrition Examination Survey (NHANES) database between 1999 and 2018. Participants were stratified into three DBP level groups. Kaplan-Meier survival curves were used to illustrate mortality distribution over time in each group. The weighted univariate and multivariate Cox regression analyses were conducted to determine the association between different diastolic blood pressure levels and all-cause and cardiovascular mortality. Additionally, restricted cubic spline analysis was applied to investigate the detailed association between DBP and hazard ratio (HR). Results: A total of 9915 patients were categorized based on their average DBP into three groups: <60 mmHg (n=2618; ILDBP), 60 to 79 mmHg (n=6208), and >=80 mmHg (n=1089; IHDBP). After weighted, the overall mean age of the participants was 58±14 years, including 47.1% male and 77.4% non-Hispanic white. Over a median follow-up period of 101.7 months, the all-cause mortality was 28.6%. Multivariate Cox regression indicated that, after adjusting for common traditional risk factors, DBP <60 mmHg was associated with a higher risk of all-cause death (HR, 1.88; 95% CI, 1.67–2.11) and cardiovascular death (HR, 1.46; 95% CI, 1.23–1.73) compared to those with DBP between 60 and 79 mmHg. Kaplan-Meier survival curves demonstrated a progressive increase in both all-cause and cardiovascular mortality as DBP decreased (log-rank P < 0.001). The restricted cubic spline analysis revealed a nonlinear relationship between DBP and all-cause mortality, identifying DBP <66.8mmHg as an independent risk factor for all-cause mortality in hypertensive patients. Conclusions: Among hypertensive patients with normalized systolic blood pressure, excessively low DBP was associated with an increased risk of all-cause and cardiovascular mortality, whereas IHDBP did not show such an association.