Greater 24 Hour Blood Pressure Variability is Associated With Higher 24 Hour Systolic Blood Pressure and Glucose Independent of Age and Large Elastic Artery Stiffness in Normotensive Adults

Older age is associated with elevated large elastic artery stiffness, a strong predictor of cardiovascular (CVD) risk in middle-age/older (MA/O) adults independent of blood pressure (BP). Greater 24-hour systolic BP variability (BPV) is also an independent risk factor for CVD and is linked to large artery stiffness in MA/O adults with hypertension and diabetes. However, its relation to age-related arterial stiffness in adults with low risk factor burden is unclear. We hypothesized that higher systolic BPV would be: 1) associated with advancing age, and 2) related to elevated aortic and carotid artery stiffness among healthy MA/O adults. To determine this, 98 healthy adults (ages 19-70 yrs) with measurements of systolic BPV (standard deviation of 24 hr systolic BP) via ambulatory BP monitoring, aortic stiffness (carotid-femoral pulse wave velocity, cfPWV), carotid artery stiffness (β-stiffness via carotid tonometry/B mode ultrasound) and circulating metabolic factors were included. In the entire cohort, greater systolic BPV was not associated with age, cfPWV, carotid β stiffness or circulating lipids/glucose (all P>0.05), but was correlated (age-adjusted) with 24 hr systolic BP (r= 0.41, P<0.001) and BMI (r= 0.21, P<0.05). In stepwise linear regression analyses that included age, sex, BMI, only 24 hr systolic BP was associated with systolic BPV (β= 0.14 ± 0.03, Model R 2 = 0.20, P< 0.001). Interestingly, there was no difference in 24 hr systolic BPV (11.4 ± 0.4 vs 11.4 ± 0.5 SD mmHg, P=0.99) in young (n=55; 29.0 ± 0.7 yrs) vs. MA/O (n= 43; 53.0 ± 1.2 yrs) adults despite higher cfPWV (594 ± 12 vs 913 ± 39 cm/sec, P<0.001), carotid β-stiffness (6.8 ± 0.6 vs 9.3 ±0.9 U, P=0.001) and 24 hr systolic BP (121 ± 1 vs 125 ± 2 mmHg, P<0.05). Systolic BPV was associated with BMI (r= 0.42, p< 0.01) and fasting blood glucose (r= 0.54, P= 0.001) in MA/O but not young adults. In a stepwise linear regression model among MA/O, 24 hr systolic BP (β= 0.18 ± 0.04, R 2 = 0.36, P<0.001) and fasting glucose (β= 0.10 ± 0.05, R 2 change= 0.07, P<0.001) were the only significant correlates of systolic BPV (Model R 2 = 0.43, P<0.001). In conclusion, 24 hr systolic BP and fasting blood glucose, but not age or large elastic artery stiffness, were the strongest determinants of higher systolic BPV in normotensive MA/O adults.