Relationships of Isolated Nocturnal Hypertension with Glomerular Filtration Rate and Albuminuria

Isolated nocturnal hypertension (INH) represents a unique phenotype that can only be identified through ambulatory blood pressure monitoring (ABPM). An increasing body of evidence suggests a significant association between INH and heightened cardiovascular morbidity, mortality, and, more recently, kidney disease progression. Considering these findings, this study aims to retrospectively assess the prevalence of INH and its relationship with glomerular filtration rate (GFR) and albumin excretion rate (AER) in a large cohort of hypertensive patients.

A total of 1340 subjects selected from the patients of our European Hypertension Excellence Centre of the University of Palermo were enrolled. Biochemical tests, urinalysis, 24 h ambulatory blood pressure monitoring, and collection of anamnestic and anthropometric data were performed on each patient.

In our cohort, the prevalence of INH was 11%. Logistic regression analyses revealed that male sex, AER, and eGFR were significantly associated with the INH phenotype. AER ≥ 5.8 µg/min predicted the presence of INH with 73.7% sensitivity and 58.4% specificity. An eGFR < 60 mL/min/1.73 m² was also correlated with INH, although its predictive value was less prominent. Multivariable regression models confirmed that AER and eGFR, along with male sex, were independent predictors of INH. In patients with normal blood pressure, AER and metabolic syndrome were also associated with INH. CKD (AER < 30 mg/day and eGFR < 60 mL/min/1.73 m²) was significantly linked to INH.

Our research confirms the direct relationship between AER and INH and the inverse relationship between GFR and INH, thus underlining the leading role of renal function in the onset of INH, as widely observed in the literature. The confirmed association between renal markers and INH in the subgroup of subjects with a clinically normal blood pressure could help us to identify the subjects who should undergo ABPM.