Characterizing Heat Health Outcomes and Informing Public Health Interventions with Medical Claims Data in California.

Area of Science:

• Environmental Health
• Public Health Policy
• Climate Change Adaptation

Background:

• Extreme heat is the leading weather-related cause of death in the U.S.
• California faces both acute heat waves and chronic heat exposure, impacting agricultural workers.
• Existing tools for allocating climate resilience resources have not been systematically evaluated against health outcomes.

Purpose of the Study:

• To map heat-related health burdens using Medicaid claims data across California ZIP codes.
• To assess the effectiveness of current vulnerability indices in identifying high-burden areas.
• To determine if state grant funding reaches communities most affected by heat-related illnesses.

Main Methods:

• Analysis of heat-related Medicaid claims from 2011-2019 across California ZIP codes.
• Comparison of claim rates with demographic data (income, farmworker population, housing type).
• Evaluation of three vulnerability indices against observed claim rates and state grant distribution.

Main Results:

• High-heat-related Medicaid claim rates correlate with lower median incomes, higher farmworker populations, and more mobile homes.
• Heat-related illness incidence increases significantly in agricultural areas compared to urban areas.
• The CDC Heat and Health Index showed the strongest correlation with observed claim rates; some high-burden counties are underfunded by state programs.

Conclusions:

• Medical claims data, combined with vulnerability indices, can improve the allocation of heat resilience funding.
• Current vulnerability indices may not fully capture the health burden of heat in all communities.
• Targeted funding adjustments are needed to support high-risk counties like Kern, Fresno, and Imperial.