Income-based inequalities in hypertension and in undiagnosed hypertension: analysis of Health Survey for England data

Objective: To quantify income-based inequalities in hypertension and in undiagnosed hypertension. Methods: We used nationally representative data from 28 002 adults (aged 16 years and older) living in private households who participated in the cross-sectional Health Survey for England 2011–2016. Using bivariate probit regression modelling, we jointly modelled hypertension and self-reported previous diagnosis of hypertension by a doctor or nurse. We then used the model estimates to quantify inequalities in undiagnosed hypertension. Inequalities, using household income tertiles as an indicator of socioeconomic status, were quantified using average marginal effects (AMEs) after adjustment for confounding variables. Results: Overall, 32% of men and 27% of women had survey-defined hypertension (measured blood pressure ≥140/90 mmHg and/or currently using medicine to treat high blood pressure). Higher proportions (38% of men and 32% of women) either self-reported previous diagnosis or had survey-defined hypertension. Of these, 65% of men and 70% of women had diagnosed hypertension. Among all adults, participants in low-income versus high-income households had a higher probability of being hypertensive [AMEs: men 2.1%; 95% confidence interval (CI): −0.2, 4.4%; women 3.7%; 95% CI: 1.8, 5.5%] and of being diagnosed as hypertensive (AMEs: men 2.0%; 95% CI: 0.4, 3.7%; women 2.5%; 95% CI: 1.1, 3.9%). Among those classed as hypertensive, men in low-income households had a marginally lower probability of being undiagnosed than men in high-income households (AME: −5.2%; 95% CI: −10.5, 0.1%), whereas no difference was found among women. Conclusion: Our findings suggest that income-based inequalities in hypertension coexist with equity in undiagnosed hypertension.