Blood pressure variability in CKD patients with and without nocturnal hypertension

Abstract

Nocturnal hypertension is highly prevalent in patients with chronic kidney disease (CKD) and represents a strong predictor of cardiovascular events. Increased blood pressure variability (BPV) is also independently associated with cardiovascular events in these patients. Differences in short-term BPV indices between CKD patients with and without nocturnal hypertension have not been previously studied. This study included 96 patients (73 with and 23 without nocturnal hypertension) who underwent 24-h ambulatory BP measurement. Standard deviation (SD), weighted SD (wSD), coefficient of variation (CV), and average real variability (ARV) of systolic (SBP) and diastolic blood pressure (DBP) were calculated using validated formulas for the 24-h and the respective daytime (07:00-23:00) and nighttime (23:00-07:00) periods. 24-h, daytime and nighttime SBP and DBP were higher in patients with nocturnal hypertension. During the 24-h period, wSD and ARV for 24-h SBP (wSD, 14.0 +/- 3.8 vs 11.7 +/- 3.1 mmHg, p = 0.009; ARV, 10.5 +/- 2.7 vs 9.2 +/- 1.9 mmHg, p = 0.035) and 24-h DBP were higher in patients with nocturnal hypertension. Regarding the daytime period, patients with nocturnal hypertension presented higher daytime SD and ARV for SBP (SD, 14.8 +/- 4.0 vs 13.0 +/- 3.6 mmHg, p = 0.008; ARV; 10.5 +/- 3.2 vs 9.1 +/- 2.0 mmHg, p = 0.016) and DBP, with daytime SBP and DBP CV being numerically but not significantly higher (p = 0.110 and p = 0.08 respectively). During the nighttime period, no significant differences between groups were present for all nighttime BPV indices. In conclusion, CKD patients with nocturnal hypertension have higher systolic and diastolic BPV indices during the 24-h and daytime periods, but not the nighttime period. These findings signify that increased BPV may be responsible for higher cardiovascular risk in CKD patients with compared to those without nocturnal hypertension.