Average real variability of 24-h systolic blood pressure is associated with microalbuminuria in patients with primary hypertension

Limited and conflicting data are available about the association between short-term blood pressure (BP) variability and urinary albumin excretion rate (uAER). The objective of our study was to analyze the relationships between microalbuminuria (MAU), defined as an uAER between 20 and 200 μg min-1, and short-term BP variability (BPV), assessed as average real variability (ARV), weighted s.d. of 24-h BP and as s.d. of daytime and night-time BP. The study population consisted of 315 untreated essential hypertensives with normal estimated glomerular filtration rate (>60 ml min-1 per 1.73 m2), who underwent 24-h ambulatory BP monitoring and 24-h uAER determination. MAU was detected in 82 (26%) patients. ARV of 24-h systolic BP (SBP) was significantly higher in patients with MAU (9.8 (8.5-11.1) mm Hg) when compared with those without it (9.1 (8-10.2) mm Hg; P=0.007). This difference held (P=0.026) after adjustment for age, mean levels of BP and other potential confounders by analysis of covariance. A statistically significant correlation was also found between ARV of 24-h SBP and uAER (r=0.17; P=0.003). This association remained significant (β=0.15; P=0.01), also taking into account the effect of 24-h average systolic and diastolic BP, age, gender, diabetes, serum uric acid, triglycerides, estimated glomerular filtration rate in multiple regression analyses. All the other indices of short-term BPV tested were not independently associated with MAU. Our results seem to suggest that in essential hypertension, short-term BPV, only when estimated by ARV of 24-h SBP, is independently associated with MAU.