Socioeconomic inequalities in blood pressure: co-ordinated analysis of 147,775 participants from repeated birth cohort and cross-sectional datasets, 1989 to 2016

Abstract

ObjectiveTo evaluate whether socioeconomic inequalities in blood pressure (BP) have changed from 1989 to 2016—a period in which average BP levels declined and the detection and treatment of high BP increased.DesignRepeated observational studies.Setting3 nationally representative British birth cohort studies—born in 1946, 1958, and 1970—and 21 nationally representative cross-sectional studies (Health Survey for England 1994 to 2016, HSE).Participants147,775 participants with BP outcomes at age 42-46 years (cohorts) or 25 years and over (HSE).Main outcome measureAbsolute differences in systolic BP (SBP) by educational attainment (cohorts and HSE) and early life social class (cohorts).ResultsIn both datasets, lower education was associated with higher SBP, with similar absolute magnitudes of inequality across the studied period. Differences in SBP by education (Slope Index of Inequality) based on HSE data were 3.0mmHg (95% CI: 1.8, 4.2) in 1994 and 4.3mmHg (2.3, 6.3) in 2016. Findings were similar for diastolic BP (DBP) and survey-defined hypertension. Cohort data suggested that disadvantage in early and adult life had cumulative independent associations with BP: cohort-pooled differences in SBP were 4.9mmHg (3.7, 6.1) in a score combining early life social class and own education, yet were 3.4mmHg (2.4, 4.4) for education alone. In both datasets, inequalities were found across the SBP distribution—below and above hypertension thresholds—yet were larger at the upper tail; in HSE, median SBP differences were 2.8mmHg (1.7, 3.9) yet 5.6mmHg (4.9, 6.4) at the 90th quantile.ConclusionSocioeconomic inequalities in BP have persisted from 1989 to 2016, despite improved detection and treatment of high BP. To achieve future reductions in BP inequalities, policies addressing the wider structural determinants of high BP levels are likely required—targeting detection and treatment alone is unlikely to be sufficient.