Background: The relationship between education and cardiometabolic biomarkers is contextually dependent on both inter-country and intra-country factors. This study aimed to examine educational differences in cardiometabolic biomarkers among middle-aged and older adults in the US, Mexico, China, and India, and whether this relationship is modified by urbanicity of residence.

Methods: Data were from contemporary cross-sectional waves of the US Health and Retirement Study (HRS; 2016/17, n = 19,608), the Mexican Health and Aging Study (MHAS; 2015, n = 12,356), the China Health and Retirement Longitudinal Study (CHARLS; 2015/16, n = 13,268), and the Longitudinal Aging Study in India (LASI; 2017/19, n = 47,838). To account for substantial variations in educational distribution across the four countries, we measured education attainment in two ways: by categorizing education levels into binary classifications (‘lower education: lower secondary education or below' vs. 'higher education: upper secondary education or above') to assess absolute education attainment, and by using within-country percentile ranks to capture relative education attainment. We assessed educational differences in four cardiometabolic biomarkers: body mass index (BMI), systolic blood pressure (SBP), glycated haemoglobin (HbA1c), and total cholesterol. We tested whether urbanicity of residence modified the relationship between education and these cardiometabolic biomarkers.

Results: The proportion of individuals with higher education was 82.6% in the US, 15.6% in Mexico, 10.6% in China, and 16.8% in India. In the US, higher education was associated with lower SBP (−2.74 mmHg, 95% CI: −3.62, −1.86) and HbA1c (−0.14%, 95% CI: −0.20, −0.08), but higher total cholesterol (3.33 mg/dL, 95% CI: 1.41, 5.25). In Mexico, higher education was associated with lower BMI only (−0.51 kg/m, 95% CI: −0.76, −0.26). In China, higher education was not associated with any biomarker. In India, higher education was associated with higher BMI (1.61 kg/m, 95% CI: 1.49, 1.73), SBP (1.67 mmHg, 95% CI: 1.16, 2.18), and HbA1c (0.35%, 95% CI: 0.19, 0.51). The association between education and cardiometabolic biomarkers was modified by urbanicity in China and India but not in the US or Mexico. In both China and India, relationships between education and cardiometabolic biomarkers were stronger among rural residents compared to those among urban residents. Results based on relative education attainment showed similar patterns in terms of the direction of the effect estimates, despite some discrepancies in statistical significance.

Interpretation: There is a complex relationship between education and cardiometabolic biomarkers across countries and by urbanicity of residence. This complexity underscores the importance of accounting for contextual factors when devising strategies to enhance cardiometabolic health in various settings.