Correlates of Systolic Blood Pressure Among Middle-Aged U.S. Adults: A Survey-weighted Regression Analysis of NHANES Data (2017 – 2018)

Abstract

Background: Hypertension is a leading modifiable risk factor for cardiovascular disease, and midlife is a critical period when adverse systolic blood pressure (SBP) trajectories emerge. We estimated nationally representative associations between SBP and demographic, socioeconomic, behavioral, and anthropometric factors among U.S. adults aged 40 - 64 years. Methodology: We analysed the National Health and Nutrition Examination Survey (NHANES) (2017–2018) Mobile Examination Center (MEC) data (N=1,884 adults). SBP was defined as the mean of up to four standardized systolic readings. Age, body mass index (BMI), and income-to-poverty ratio (PIR) were treated as continuous predictors. Gender, race/ethnicity, smoking status, and doctor-advised physical activity were modelled as categorical covariates. We compared main-effects and interaction models using the Bayesian Information Criterion. The main-effects model was selected and estimated using survey-weighted linear regression with MEC examination weights, strata, and primary sampling units to obtain population-level estimates. Results: SBP increased with age (0.56 mmHg per year; 95% CI: 0.34, 0.78; p = 0.004) and BMI (0.47 mmHg per kg/m²; 95% CI: 0.23, 0.71; p = 0.008). Compared with non-Hispanic White adults, SBP was 9.01 mmHg higher among non-Hispanic Black adults (95% CI: 6.09, 11.93; p = 0.002) and 4.56 mmHg higher among non-Hispanic Asian adults (95% CI: 0.40, 8.72; p = 0.040). PIR showed an inverse but non-significant association (−0.75 mmHg; 95% CI: −1.74, 0.25; p = 0.096). Gender differences, Smoking status and doctor-advised physical activity were not statistically significant. Conclusions: Among middle-aged U.S. adults, SBP was associated with age and adiposity. Racial and ethnic differences persisted, with SBP about 9 mmHg higher among non-Hispanic Black adults and 5 mmHg higher among non-Hispanic Asian adults compared with non-Hispanic White adults. These findings emphasise the need for midlife weight management and equity-focused hypertension prevention strategies.