Changing epidemiology of non-occupational acute carbon monoxide poisoning and the increasing share of older adults during the clean heating transition: a 10-year emergency department study in rural Tianjin, China.

Background and Objective: Non-occupational Acute Carbon Monoxide Poisoning (ACOP) remains a preventable emergency condition in northern rural China, where winter heating and indoor combustion have historically been important exposure sources. In rural Tianjin, the clean heating transition period was accompanied by a substantial decline in the overall incidence of non-occupational ACOP, while the residual burden shifted toward older adults and lifestyle-related exposure sources. However, whether this transition has changed the epidemiological profile of non-occupational ACOP, particularly the residual risk among older adults, remains unclear. This study aimed to examine changes in the incidence, demographic profile, exposure sources, and severity of non-occupational ACOP during the clean heating transition in rural Tianjin, China, with special attention to older adults. Methods: This single-center retrospective observational study included patients with non-occupational ACOP who presented to the Emergency Department of Tianjin Jizhou District People's Hospital between January 2016 and December 2025. The study period was divided into a policy construction and transition period (2016-2019) and a policy implementation and consolidation period (2020-2025). Annual emergency department-attended (ED- attended) incidence rates were calculated using resident population data. Demographic characteristics, exposure sources, seasonal distribution, clinical severity, and outcomes were compared between the two periods. Negative binomial regression was used to estimate incidence rate ratios because the annual case counts were substantially overdispersed, with quasi-Poisson, robust-variance Poisson and standard Poisson models fitted as concordant sensitivity analyses, and exploratory logistic regression was performed to assess factors associated with severe poisoning, including death. Results: A total of 3,923 patients were included, with 2,241 cases during 2016-2019 and 1,682 cases during 2020-2025. The ED- attended incidence, calculated using emergency department-treated ACOP cases and resident population denominators, decreased from 0.620 to 0.356 per 1,000 population, corresponding to a 42.7% reduction during 2020-2025 (negative binomial IRR = 0.573, 95% CI: 0.432-0.759, Conclusion: During the clean heating transition in rural Tianjin, the ED-attended incidence of non-occupational acute carbon monoxide poisoning declined substantially in both age groups, but older adults came to account for an increasing share of the remaining cases, and charcoal hotpot use accounted for a growing proportion of residual exposures. These findings suggest that clean heating consolidation should be complemented by targeted geriatric risk management, winter safety education, carbon monoxide alarm promotion, safe charcoal use, and community-based prevention strategies for older adults living in rural and semi-rural settings.