Masked hypertension common in CKD, especially with elevated nighttime blood pressure

Masked hypertension, or blood pressure that is normal at the doctor's office but high on ambulatory monitoring, is common in patients with chronic kidney disease (CKD) and is associated with target organ damage, according to a recent study.

Researchers performed a cross-sectional study of 1,492 men and women with CKD who were participating in the Chronic Renal Insufficiency Cohort Study. Patients were categorized as having controlled blood pressure (clinic measurement <140/90 mm Hg, 24-hour measurement <130/80 mm Hg), white-coat hypertension (clinic measurement ≥140/90 mm Hg, 24-hour measurement <130/80 mm Hg), masked hypertension (clinic measurement <140/90 mm Hg, 24-hour measurement ≥130/80 mm Hg), or sustained hypertension (clinic measurement ≥140/90 mm Hg, 24-hour measurement ≥130/80 mm Hg). In addition, 1,278 patients received echocardiography and 1,394 had measurements of pulse wave velocity (a measure of arterial stiffness in which higher velocities are associated with increased risk of cardiovascular disease).

The goal of the study was to determine the association between masked hypertension and kidney function and signs of cardiovascular target organ damage, as well as to evaluate whether the association differed in patients with and those without elevated nighttime blood pressure. The study results were published online Feb. 18 by the Clinical Journal of the American Society of Nephrology.

Of the 1,492 patients in the study, 55.8% were men and 38.9% were of non-Hispanic black ethnicity. Mean age was 63.1 years. Overall, 49.3% of patients had controlled blood pressure, 4.1% had white-coat hypertension, 27.8% had masked hypertension, and 18.8% had sustained hypertension. Masked hypertension was independently associated with low estimated glomerular filtration rate (eGFR) (−3.2 mL/min per 1.73 m²; 95% CI, −5.5 to −0.9 mL/min per 1.73 m²), as well as with higher proteinuria, higher left ventricular mass index, and higher pulse wave velocity, compared with controlled blood pressure. Sustained hypertension was also associated with low eGFR and elevated proteinuria. A more pronounced association was seen between low eGFR and masked and sustained hypertension in patients whose nighttime blood pressure was elevated versus those whose nighttime blood pressure was below 120/70 mm Hg (P=0.002 for interaction).

The authors noted that their study could not assess causality because of its cross-sectional and observational design and that they obtained only 1 measurement of ambulatory blood pressure, among other limitations. However, they concluded that masked hypertension occurs commonly in patients with CKD and that it is associated with lower eGFR, proteinuria, and cardiovascular target organ damage. Elevated nighttime blood pressure is also associated with low eGFR and proteinuria, the authors said. “[Ambulatory blood pressure] may better characterize the relationship between [blood pressure] and adverse outcomes in patients with CKD,” they wrote. They called for additional studies to evaluate whether adverse clinical events in patients with CKD can be reduced by basing treatment on ambulatory blood pressure monitoring.