An unexpected paradox: examining the relationship between solid fuel heating and reduced cancer risk in CHARLS

AIM: While solid fuel use is a known health concern, its specific link to cancer incidence via heating in China’s elderly remains unclear. This study investigated this association using data from the China Health and Retirement Longitudinal Study (CHARLS). METHODS: The research used data from CHARLS. The primary exposure variable was the use of solid fuels for heating. The primary outcome was incident cancer. All statistical analyses were performed utilizing SPSS software (version 25.0) and R software (version 4.4.4). RESULTS: We analyzed 6,753 participants without baseline cancer. The primary exposure was solid fuel use for heating, and the outcome was incident cancer. Logistic regression models were used, adjusting for confounders. Over a nine-year follow-up, 299 (4.43%) participants developed cancer. Contrary to the initial hypothesis, solid fuel use for heating was statistically associated with a lower cancer risk (adjusted OR = 0.77, 95% CI: 0.61–0.98). Mediation analysis indicated depressive symptoms, LDL-C, and total cholesterol masked portions of this effect. Subgroup analyses showed the association was more pronounced in specific demographics. CONCLUSION: This study reveals a paradoxical statistical link between solid fuel heating and reduced cancer risk. We strongly caution against interpreting this as a biological causal effect. Instead, methodological factors and sociodemographic biases—such as healthcare access, socioeconomic status, and detection bias—are likely critical contributors. These findings highlight the importance of accounting for structural biases in health research to avoid misleading conclusions.