Long-term effects of public health insurance on the health of children in Mexico: a retrospective study

On Dec 1, 2006, Mexico's public health-care insurance scheme, Seguro Popular, implemented the Medical Insurance Century XXI (SMSXXI) programme, to provide insurance to children younger than 5 years without social security. SMSXXI aims to increase access to health services, decrease out-of-pocket health expenses (OOPHE), and reduce health inequities. SMSXXI covers uninsured, primarily low-income, populations who might be most at risk of the financial and health consequences of costly medical interventions. We assessed the effects of SMSXXI on health outcomes and financial protection for Mexico's children using multiple nationally representative surveys and administrative data sources spanning 2001–16. The identification of effects relied on detailed hospital-level affiliation data mapping the geographical expansion of SMSXXI's coverage across the country over time. The units of analysis included hospitals, households, and children. Primary outcomes were neonatal and infant mortality, self-reported morbidity (health status, influenza, and diarrhoea), and child's height. Secondary outcomes were OOPHE, hospital discharges, and quality of service provision. Effects controlled for fixed and time-variant confounders using double-difference and triple-difference estimation strategies. Where feasible, we also estimated effects using exogenous variation in programme eligibility rules that limited enrolment in SMSXXI to children born after Dec 1, 2006. SMSXXI was not associated with early (