High prevalence and incidence of hypertension among South Africans starting ART

There is a high prevalence and incidence of hypertension (raised blood pressure) among HIV-positive people starting antiretroviral therapy (ART) in South Africa, according to research published in PLOS One. A fifth of people were hypertensive when they started ART and a further 15% developed hypertension during follow-up.

Traditional risk factors, including age over 40 years and being overweight or obese were predictors of hypertension, as was therapy with some older antiretrovirals. Only a minority of hypertensive people received treatment for their condition.

“Our work adds to the evidence base on hypertension and its risk factors in settings of both high HIV prevalence and the non-HIV risk factors common in middle-income countries,” comment the authors. “Older patients, males, those on nevirapine, zidovudine or stavudine, and those who are overweight/obese should be targeted for frequent blood pressure monitoring and the identification of other cardiovascular risk factors to encourage lifestyle modifications.”

Hypertension is a key risk factor for the development of cardiovascular disease. An estimated 1 billion people globally are hypertensive and raised blood pressure is estimated to kill 15 million people each year. Prompt diagnosis of hypertension is important as the condition can be controlled through lifestyle modifications (stopping smoking, improvements in diet, weight loss, frequent exercise) and effective medication is also available. The incidence and prevalence of hypertension in low- and middle-income settings, including sub-Saharan Africa, is increasing.

As access to ART is scaled up and deaths from AIDS-defining conditions decline, the management of hypertension is emerging as an essential part of HIV care in low- and middle-income countries.  Cardiovascular disease is an increasingly important cause of morbidity and mortality among South African ART-treated individuals.

A team of investigators designed a prospective, observational study to determine the prevalence, incidence, predictors and control of hypertension among HIV-positive adults starting ART.

A total of 77,696 people enrolled in the Right to Care Clinical HIV cohort were included in the analysis. All started ART at a publicly funded clinic between 2004 and 2016. ART was based on a non-nucleoside reverse transcriptase inhibitor (NNRTI) and lamivudine plus stavudine, zidovudine, or after 2010, tenofovir.

The primary outcomes were prevalent hypertension at ART initiation and incident hypertension during ART. Prevalent hypertension was defined as a single blood pressure measurement of 140/90 mm/Hg or above in the three months before starting ART, a pre-existing diagnosis of hypertension, or the use of hypertensive drugs.

People with normal blood pressure at baseline were diagnosed with incident hypertension if they met any of the following criteria after ART initiation:

• At least three blood pressure measurements, at least two days apart above 140/90 mm/Hg (or 130/80 mm/Hg in the presence of co-morbidities)
• A single blood pressure measurement above 180/110 mm/Hg
• Documented hypertension in a patient’s note
• Documented treatment for hypertension.

Just under two-thirds (61%) of the cohort were female and the median age at ART initiation was 37 years. Median baseline blood pressure was 117/76 mm/Hg. Average BMI was 22.1kg/mm². A stavudine-containing regimen was started by 48% of people, an equal proportion initiating a combination containing tenofovir.

More than a fifth (22%) of people were hypertensive at baseline. Older people (40 years and older) and individuals classified as overweight or obese were significantly more likely to be hypertensive. Poorer health status, including advanced HIV disease and low haemoglobin, was associated with a lower risk of hypertension.

People with baseline hypertension were excluded from further analysis, leaving a sample of 60,570 people. During follow-up, 13% of these people were diagnosed with hypertension at a median of 13 months after ART initiation. Overall incidence was 5.44 per 100 person-years.

In addition to age, risk factors for incident hypertension included male sex (HR = 1.23; 95% CI, 1.14-1.32) and pre-hypertension (HR = 2.05; 95% CI, 1.92-2.19). People with a baseline CD4 cell count below 50 cells/mm³ were 25% more likely to be diagnosed with incident hypertension compared to those with a CD4 cell count at ART initiation above 350 cells/mm³.

Certain antiretrovirals were also associated with a diagnosis of hypertension. People treated with nevirapine were 27% more likely to develop incident hypertension compared to those who started therapy with efavirenz. People starting stavudine and zidovudine were 40% more likely to develop hypertension than those initiating tenofovir.

A quarter of people with incident hypertension received treatment for elevated blood pressure. More than half (58%) continued to have elevated blood pressure a median of five months after receiving blood pressure medication. A small proportion (2%) developed an illness related to hypertension.

Analysis of the 76% of people who did not receive blood pressure medication showed that 54% still had elevated blood pressure six months after their initial diagnosis of hypertension. A blood pressure-related co-morbidity was reported in approximately 2% of people.

“Over 20% of patients in our cohort had hypertension at ART initiation, and 13% of those with normal blood pressure at ART initiation developed hypertension while on ART,” conclude the authors. “At risk populations should be offered pharmaceutical therapy to help prevent myocardial infarction, heart failure, stroke, and kidney disease. Further research is needed to determine the level of access and adherence to pharmaceutical treatment for hypertension in this population. Additionally, an HIV-negative comparison population is needed to assess the association of the HIV virus itself with hypertension.”