Nocturnal blood pressure: the dark side of white-coat hypertension

The impact of defining white-coat hypertension (WCH) and white-coat uncontrolled hypertension (WCUH) based on daytime and night-time thresholds of ambulatory blood pressure (ABP), instead of 24-h mean value, is unclear. We aimed to reclassify BP status according to both diurnal and nocturnal thresholds in a large sample of hypertensive patients seen in a specialist center and previously classified as WCH and WCUH based on 24-h BP values.

A data-base of 7353 individual 24-h ABP monitoring (ABPM) from untreated and treated hypertensive individuals with office BP at least 140 mmHg and/or 90 mmHg was analysed and a subset of 3223 patients characterized by mean 24-h BP less than 130/80 mmHg (i.e. WCH and WCUH) was included in the present analysis.

As many as 1281 patients were classified as WCH and 1942 as WCUH. Among them, elevated out-of-office BP according to night-time threshold (i.e. ≥120/70 mmHg) was found in about 30% of cases. In particular, prevalence rates of nocturnal hypertension were 26.9% in WCH and 31.8% in WCUH. Isolated daytime hypertension (i.e. ≥135/85 mmHg) was detected in an additional 4% of individuals.

Classification of WCH and WCUH based on mean 24-h BP thresholds does not allow to detect an adverse BP phenotype, such as nocturnal hypertension in a large fraction of untreated and treated patients.