Extreme weather events and liver cancer mortality in Shandong Province, China: Identifying vulnerabilities and health inequalities

Background: Cancer remains a major global health issue, yet the effects of climate change, particularly extreme weather events, on people at high risk of cancer are not clear. This study aimed to investigate the short-term effects of heatwaves and cold spells on liver cancer mortality and identify high-risk subpopulations.Methods: Daily liver cancer mortality in Shandong Province from 2012 to 2020 was obtained from the Death Surveillance System. A two-step approach was employed. First, distributed lag non-linear models were applied to quantify the impact of heatwaves and cold spells on liver cancer mortality at a lag of 0–7 days. Second, city-specific relative risk (RR) was pooled using meta-regressions for overall risk estimates. Subgroup analyses were conducted to identify vulnerable groups.Results: A total of 220 613 liver cancer deaths were recorded in Shandong Province from 2012 to 2020. Heatwaves (≥ 90th percentile) were associated with increased liver cancer mortality risk, peaking at a 4-day duration [RR = 1.035, 95% confidence interval (CI): 1.008–1.063]. Cold spells (≤ 2.5th percentile, lasting ≥ 4 days) showed a peaked effect (RR = 1.167, 95% CI: 1.006–1.353). Subgroup analysis revealed heightened risk among females, individuals aged < 45 years and ≥ 65 years, and populations in regions with high incomes and lower healthcare expenditures.Conclusions: Extreme temperature events are associated with increased liver cancer mortality. Vulnerable groups such as females, the elderly, young individuals, and residents in economically advantaged regions and less healthcare investment are disproportionately affected. Findings underscore the importance of targeted interventions to mitigate climate-related health risks in vulnerable populations.