Low correlation between visit-to-visit variability and 24-h variability of blood pressure

visit-to-visit variability (VVV) of clinic systolic blood pressure (SBP) has been associated with cardiovascular disease risk. Given the need for obtaining blood pressure (BP) at multiple visits to calculate VVV, substituting BP variability from ambulatory blood pressure monitoring (ABPM) may be a practical alternative. We assessed the correlation between VVV of BP and BP variability from ABPM using data from 146 untreated, mostly normotensive participants (mean age 47.9 years), in a substudy of the ongoing Masked Hypertension Study. VVV of SBP and diastolic blood pressure (DBP) was estimated by the standard deviation (s.d.vvv) and average real variability (ARVvvv) from six study visits over a median of 216 days. ABPM data were used to calculate the day-night s.d. (s.d.dn), and the ARV of SBP and DBP over 24 h (ARV24). For SBP, the mean s.d.vvv and s.d.dn were 6.3 (s.d.=2.5) and 8.8 mm Hg (s.d.=1.8), respectively, and mean ARVvvv and ARV24 were 7.2 (s.d.=3.2) and 8.4 mm Hg (s.d.=2.1), respectively. Spearman's correlation coefficient between s.d.vvv and s.d.dn of SBP was rs=0.25, and between ARVvvv and ARV24 was rs=0.17. Participants in the highest quartile of s.d.dn of SBP were 1.66 (95% CI: 0.93-2.75) times more likely to be in the highest quartile of s.d.vvv of SBP. The observed-to-expected ratio between the highest quartiles of ARVvvv and ARV24 of SBP was 0.89 (95% CI: 0.41-1.69). The correlations for s.d.vvv and s.d.dn, and ARVvvv and ARV24 of DBP were minimal. These data suggest VVV and 24-h variability are weakly correlated and not interchangeable.