Indoor solid fuel use and incident arthritis among middle-aged and older adults in rural China: A nationwide population-based cohort study

Many households in developing countries, including China, rely on the traditional use of solid fuels for cooking and heating. Arthritis is highly prevalent in middle-aged and older adults and is a major cause of disability. However, evidence linking indoor solid fuel use with arthritis is scarce in this age group (≥45 years) in developing countries. To investigate whether exposure to indoor solid fuel for cooking and heating is associated with arthritis in middle-aged and older adults in rural China. Data for the present study were extracted from the China Health and Retirement Longitudinal Study (CHARLS), a longitudinal national prospective study of adults aged 45 years and older enrolled in 2010 and followed up through 2015. We included 7807 rural participants without arthritis at baseline, of whom 1548 living in a central heating area in winter were included in the heating analysis (taking the Qinling-Huaihe line as the heating boundary). Cox proportional hazards models were used to examine the association between indoor solid fuel use and arthritis, controlling for age, sex, education, marital status, smoking status, drinking status, self-reported socioeconomic status, BMI, sleep time, napping time, independent cooking, hypertension, diabetes, dyslipidemia, heart problems and stroke. We also investigated the effect of switching primary fuels and using solid fuels for both cooking and heating on arthritis risk. The mean (SD) age of the study participants was 59.2 (10.0) years old, and 48.0% of participants were women. A total of 64.8% and 63.0% of the participants reported primarily using solid fuel for cooking and heating, respectively. Arthritis incidence rates were lower among clean fuel users than solid fuel users. Compared to those using clean fuels, cooking and heating solid fuel users had a higher risk of arthritis, with hazard ratios (HRs) of 1.22 (95% confidence interval (CI): 1.01, 1.49) and 1.76 (95% CI: 1.07, 2.89), respectively. Switching from clean fuels to solid fuels for heating (HR: 3.28, 95% CI: 1.21, 7.91) and using solid fuels for both cooking and heating (HR, 1.71, 95% CI, 1.01–2.79) increased the risk of arthritis. Long-term solid fuel use for indoor cooking and heating is associated with an increased risk of arthritis events among adults aged 45 years and older in rural China. The potential benefits of reducing indoor solid fuel use in groups at high risk for arthritis merit further exploration.