This study examines whether childhood blood lead levels (BLLs) covary with the prevalence of reported marriage to a blood relative across Indian states. State-level mean BLLs were taken from the IHME GBD 2021 estimates for children aged 5–9 years in 1995. State-level prevalence was estimated from NFHS-5 (2019–21) records for 405,314 ever-married women across 17 states. A positive ecological association was observed (Pearson r = 0.62, p = 0.008; Spearman ρ = 0.56, p = 0.019). The associationstrengthened after adjustment for state net domestic product per capita (partial r = 0.76, p = 0.0004) and remained present after adjustment for a coarse North–South kinship-region indicator (partial r = 0.51, p = 0.035). However, leave-one-out analysis reveals that the after-South partial correlation depends heavily on Kerala: removing it reduces the partial r from 0.51 to 0.10. The association was not evident within northern states alone (r = 0.12). Restricting to women aged 25–35, whose childhood most closely aligns with the 1995 BLL reference year, did not materially change results (r = 0.61). A supplementary cross-national analysis showed a weaker but directionally similar pattern (non-OECD n = 21: partial r = 0.51 after GDP). These findings are descriptive and hypothesis-generating only. They may reflect shared regional structure, model-induced correlation, the influence of a single state, reverse causation, or other confounding rather than any causal effect. Replication with district-level data is needed.
Roman Petrov (Fri,) studied this question.