Masked Hypertension in Low-Income South African Adults

Abstract

While South Africa has one of the highest hypertension rates globally, there are few data on masked hypertension (MHT) and white-coat hypertension (WCHT). This study measured the frequency of MHT and WCHT in low-income (<$500 US per month) South African adults, evaluating cardiovascular risk by arterial stiffness. Participants (n=101, 50% male; mean age 39.4±9.7 years) were recruited from a large North-West Province employer. Clinic and 24-hour blood pressure (BP) and pulse wave analysis were recorded. Clinic BP identified 18% of patients as hypertensive, while 24-hour BP showed that 63% of patients were hypertensive. The frequency of MHT was high (33 of 81, 41%) with only one case of WCHT. In comparison to those with normal clinic and 24-hour BP, augmentation index and pulse wave velocity were significantly higher in those with hypertensive 24-hour BP irrespective of clinic BP, indicating that, in this group, masked and sustained hypertension carry a similar elevated cardiovascular risk.

Figure 1

Study flow diagram. ABPM indicates ambulatory blood pressure monitoring; BP, blood pressure.

Figure 2

Twenty‐four–hour ambulatory blood pressure measures in patients with normotension (NT, n=25), masked hypertension (MHT, n=33), and sustained hypertension (HT, n=20). The shaded area shows the nighttime period. Results of Bonferroni post‐hoc analysis: ^aboth hypertensive groups significantly different than the NT group; ^bsustained hypertensive group significantly different than the MHT and NT groups; ^csignificant difference between all three groups; ^dHT group significantly different than the NT group; and ^eMHT group significantly different than the NT group; all P<.05.

Figure 3

Twenty‐four–hour pulse wave velocity (PWV) measures in patients with normotension (NT, n=24), masked hypertension (MHT, n=33), and sustained hypertension (HT, n=20). PWV adjusted for age and group mean arterial pressure. Shaded area shows the nighttime period. Results of Bonferroni post‐hoc analysis: ^aboth hypertensive groups significantly different than the NT group, and ^dsignificant difference between all three groups; all P<.05.