Progress, stasis, and regression through the hypertension care continuum: Longitudinal evidence from population-based cohort data in four populous middle-income countries

BackgroundControlling and managing hypertension is a highly dynamic process yet, to our knowledge, existing evidence on hypertension control gaps in middle-income countries (MICs) is largely based on cross-sectional data. We provide the first longitudinal investigation of how individuals with hypertension move through the care continuum over time across multiple MICs. MethodsWe used multiple waves of population-based longitudinal cohort data from China, Indonesia, Mexico and South Africa. Based on measured blood pressure and information on hypertension diagnosis and treatment status, we classified adults aged 40 + into four care stages at both the baseline and follow-up waves: undiagnosed; diagnosed and untreated; diagnosed, treated, but uncontrolled (systolic blood pressure (SBP) [≥] 140 mmHg or diastolic blood pressure (DBP) [≥] 90 mmHg); diagnosed, treated, and controlled (SBP < 140 mmHg and DBP < 90 mmHg). We estimated the probability of individuals progressing forward or regressing backwards through the continuum over a five-to nine-year between-wave period and investigated how these probabilities varied by age, sex, household location and educational attainment using Poisson regression models. We also estimated the probabilities of important clinical transitions (e.g. becoming diagnosed or treated; achieving blood pressure control; discontinuing treatment and losing blood pressure control). FindingsOur data included 8359 individuals with hypertension (China: N=1371, Indonesia: N= 3438, Mexico: N=1946, South Africa: N=1604). Across all countries, there was a less than 50% probability of forward progression through the care continuum over time. Just over one in four undiagnosed individuals became diagnosed (China 30% [95% CI 26-33%], Indonesia 30% [95% CI 28-32%], Mexico 27% [95% CI 25-29%], South Africa 37% [95% CI 34-39%]) and one in three diagnosed, untreated individuals became treated (Indonesia 17% [95% CI 14-21%], Mexico 30% [95% CI 28-32%], China 48% [95% CI 39-56%], South Africa 42% [95% CI 40-44%]). Importantly, there were very high probabilities of regressing to less advanced continuum stages: up to nine in ten treated and controlled individuals lost blood pressure control (Indonesia 92% [95% CI 88-95%], Mexico 77% [95% CI 72-81%], China 76% [95% CI 68-83%], South Africa 48% [95% CI 42-54%]) and up to three in four individuals discontinued treatment over the follow-up period (China 36% [95% CI 32-41%], Indonesia 70% [95% CI 67-73%], Mexico 34% [5% CI 32-36%], South Africa 25% [23-27%]). Individuals from rural households were disadvantaged in all countries but China, while females were more likely to progress through the continuum in Indonesia and Mexico. InterpretationOur results uncover critical gaps in hypertension care in MICs in both early and late stages of the continuum. Adopting a longitudinal perspective reveals that policies solely aimed at improving diagnosis or initiating treatment may not lead to large improvements in control, as treatment initiation rates are low and achievement of blood pressure control and adherence to therapy are rarely sustained over time. RESEARCH IN CONTEXTO_ST_ABSEvidence before this studyC_ST_ABSWe searched PubMed for articles published from database inception until January 1st, 2021 using variations of the search terms "blood pressure", "hypertension", "continuum", "cascade", "treatment", "diagnosis", "control", "treated", "diagnosed", "controlled" to screen titles and abstracts. The currently largest studies estimating nationally representative levels of hypertension diagnosis, treatment and control across multiple low- and middle-income countries (LMICs) are the Prospective Urban Rural Epidemiology (PURE) study from 2013, which included 140 000 individuals across 14 LMICs and a more recent study based on 1{middle dot}1 million adults in 44 LMICs from 2019. Both studies highlight important gaps in awareness, diagnosis, treatment and control of hypertension across populations in LMICs. However, these and smaller non-nationally representative or single country studies are all based on cross-sectional data and none capture the dynamic nature of chronic disease care and how individuals move through the hypertension care continuum over time. Added value of this studyTo our knowledge, we provide the first longitudinal evidence on how individuals with hypertension in middle-income countries (MICs) move through the hypertension care continuum over time using country-wide, longitudinal cohort data from four MICs, which span three different continents and account for close to one-fourth of the world population. The longitudinal perspective provides new insights over existing cross-sectional cascades by capturing critical dynamic elements of chronic disease management, such as how individuals arrived at a specific continuum stage or whether they move forward or backward through continuum stages over time. Implications of all available evidenceOur results reveal that individuals rarely sustain blood pressure control and that they tend to discontinue treatment over time. These results can inform efforts to improve hypertension control by revealing the need to move beyond policies aimed solely at screening and diagnosis to those that also aim to help individuals sustain blood pressure control over time.