The impact of human development on individual health: a causal mediation analysis examining pathways through education and body mass index

BACKGROUND The macro environment we live in projects what we can achieve and how we behave, and in turn, shapes our health in complex ways. Policymaking will benefit from insights into the mechanisms underlying how national socioeconomic context affects health. This study examined the impact of human development on individual health and the possible mediating roles of education and body mass index (BMI). METHODS We analyzed World Health Survey data on 109,448 participants aged 25 or older from 42 low- and middle-income countries with augmented human development index (HDI) in 1990. We used principal components method to create a health score based on measures from eight health state domains, used years of schooling as education indicator and calculated BMI from self-reported height and weight. We used causal mediation analysis technique with random intercepts to account for the multilevel structure. RESULTS Below a reference HDI level of 0.48, HDI was negatively associated with good health (total effect at HDI of 0.23: b =  - 3.44, 95% CI [-6.39--0.49] for males and b =  - 5.16, 95% CI [-9.24,--1.08] for females) but was positively associated with good health above this reference level (total effect at HDI of 0.75: b = 4.16, 95% CI [-0.33-8.66] for males and b = 6.62, 95% CI [0.85-12.38] for females). We found a small positive effect of HDI on health via education across reference HDI levels (b ranging from 0.24 to 0.29 for males and 0.40 to 0.49 for females) but not via pathways involving BMI only. CONCLUSION Human development has a non-linear effect on individual health, but the impact appears to be mainly through pathways other than education and BMI.