Modeling climate change health outcomes using ICD-10 "exposure to forces of nature" diagnosis codes

The aim of this research is to determine whether ICD-10 codes for exposure to forces of nature (X30-X32, X36-X38) can be used to examine disparities in X-code documentation and associations with in-hospital mortality. Binary logistic regression of 169.5 million discharge records from the 2018-2022 National Inpatient Sample was conducted to examine associations between social determinants of health variables, presence of X-codes, and in-hospital mortality. Only 0.055% (93,860) records included X-codes, increasing 32% from 2018 (0.053%) to 2022 (0.070%). Female patients had 65.5% lower odds of documentation (OR = 0.345). Medicaid beneficiaries had 2.6 higher odds (OR = 2.59). Hispanic and Asian/Pacific Islander patients were systematically undercoded (OR = 0.665 and OR = 0.649, respectively). Native American populations had higher odds of documentation (OR = 2.62). X-codes were independently associated with 60% increased odds of in-hospital mortality (adjusted OR = 1.60, 95% CI: 1.55-1.66). ICD-10 X-codes represent a viable, yet underutilized surveillance infrastructure for climate health outcomes, with mortality associations validating their clinical significance. However, the very low prevalence of X-codes (0.055%) and systematic documentation inequities suggest that climate-related exposures may be underrecognized in administrative data and support the need for enhanced clinician awareness, standardized coding protocols, and explicit equity integration for effective climate health surveillance.