Ethnicity and socio-economic inequalities in malignant hypertension

In 1999, it was claimed at a meeting hosted by the Department of Veterans Affairs in Washington that ‘malignant hypertension had disappeared’. However, the paper summarizing the meeting was more conservative. It stated ‘Originally seen in all 4 race/gender groups (whites and blacks, men and women), [malignant hypertension] tended to disappear, first in whites of either gender and then in black women, while becoming much less frequent in black men. This disappearance has usually been ascribed to the widespread treatment, at least minimal treatment, of severe diastolic hypertension’ ^[1]. Nonetheless, many hypertension units continue to see patients with malignant hypertension ^[2–6], and some reports have described the incidence of the condition as low but stable ^[2,5]. Mortality from malignant hypertension has declined, thanks to chronic renal replacement therapy, but epidemiological data on the declining incidence of the condition is lacking ^[7]. Malignant hypertension has thus not proven to be the vanishing disease it promised to be in the 1970s ^[8].

Patients with severe or malignant hypertension often have poor access to the health system due to psychosocial or linguistic barriers ^[9–11]. In Europe, many Africans and Afro-Caribbeans are first-generation migrants with a high degree of socio-economic deprivation. In this issue of the journal, van den Born et al. ^[12] analyse ethnic disparities in the incidence and consequences of malignant hypertension. In a cohort of 122 patients, the incidence of malignant hypertension was more than four-fold higher in blacks than in whites, with no apparent decline over the 12 years of the study. Blacks had higher systolic blood pressure and serum creatinine levels than whites and had a poorer renal outcome: after a mean follow-up of 4 years, they had an unadjusted hazard ratio of 2.8 for requiring renal replacement therapy. As might be expected, the higher risk of a requirement for dialysis was linked to higher serum creatinine levels at referral. When corrected for baseline creatinine concentrations, the relationship between ethnicity and renal failure was no longer significant.

Many of the findings of van den Born et al. ^[12] concerning malignant hypertension (i.e. the over-representation of black patients, higher blood pressure and creatinine levels and poorer outcome in this ethnic group) confirm results previously published by Lip et al. ^[2,3]. What van den Born's study adds is an emphasis on the socio-economic dimension of the poor outcome of black patients with malignant hypertension. At referral, 18 of 57 (32%) black and ten of 65 (15%) white patients had stopped taking previously prescribed antihypertensive medication. Fourteen black patients (25%) and only one white patient (2%) had no medical insurance. During follow-up, blood pressure was controlled in only 32% of black patients versus 56% of white patients. Van den Born's study provides no comparison of the number of follow-up visits, attendance at scheduled visits, probability of referral to a nephrologist, compliance with antihypertensive medication, or the nature and cost of antihypertensive prescriptions, between black and white patients following the diagnosis of malignant hypertension. However, the persistence of an ethnic difference in blood pressure control during follow-up suggests that the inequalities in access to health care present before referral persisted during long-term follow-up. In black patients without medical insurance, at least, access to specialized health care and compliance with long-term antihypertensive medication were probably less than optimal. It is also possible than angiotensin-converting enzyme inhibitors, which prevent the progression of hypertensive kidney disease in Afro-Americans more efficiently than conventional antihypertensive drugs ^[13], but which are also more expensive, were prescribed less frequently in black patients with no medical insurance.

Blacks have a higher risk of developing end-stage renal disease due to hypertension than whites ^[14]. It is probably more difficult to achieve blood pressure control in blacks than in whites, particularly in subjects with compromised renal function. However, ethnic differences in hypertension control can be reduced by ensuring that black and white hypertensive patients have equal access to health care ^[15].

Ten years after the reports from the UK and Italy ^[2–5], this report from Amsterdam by van den Born et al. ^[12] indicates that the incidence of malignant hypertension remains stable, even in European regions with a high quality of care. It highlights the higher frequency and greater severity of this condition in disadvantaged minorities. The primary prevention of malignant hypertension is very difficult to achieve. Because we still do not understand why a minority of patients with severe hypertension develop the fibrinoid necrosis of arterioles characteristic of malignant hypertension ^[11], primary prevention of this condition would necessarily involve a very large number of patients. However, given the very small number of patients who develop malignant hypertension and the enormous cost of renal replacement therapy, it would be reasonable, and probably cost-effective, to provide all patients who have had malignant-phase hypertension, and black patients in particular, with free access to high-quality medical care.