The relationship between cooking fuel use and sex hormone levels: A cross-sectional study and Mendelian randomization study

The aim of this study was to investigate the effect of solid fuel use on serum sex hormone levels. Furthermore, the effects of improved kitchen ventilation and duration of cooking time on the relationship between solid fuel use and serum sex hormone levels will be further explored. In this cross-sectional study, 5386 individuals were recruited. Gender and menopausal status modified associations between solid fuel type and serum sex hormone levels was investigated through generalized linear models and further analyzed by improving kitchen ventilation and length of cooking time on the relationship between solid fuel use and serum sex hormone levels. To identify the causal association, mendelian randomization of two-sample was performed. In observational analyses, for ln-17-hydroxyprogesterone, ln-testosterone, and ln-androstenedione among premenopausal women, the estimated β and 95 % CI of sex hormone levels for the effect of solid fuel users was −0.337 (−0.657, −0.017), −0.233 (−0.47, 0.005), and − 0.240 (−0.452, −0.028) respectively, and − 0.150 (−0.296, −0.004) in ln-progesterone among postmenopausal women. It was found that combining solid fuels with long cooking periods or no ventilation more effectively reduced testosterone and androstenedione in premenopausal women. We further found the adverse effects of using solid fuel on progesterone, testosterone, and androstenedione levels were enhanced with the increases of PM1, PM2.5, PM10, and NO2. Corresponding genetic, the causal risk effect of solid fuel were − 0.056 (−0.513, 0.4) and 0.026 (−3.495, 3.547) for testosterone levels and sex hormone binding globulin, respectively. Using gas or solid fuel was negatively related to sex hormone levels. A combination of using solid fuels, cooking for a long time, or cooking without ventilation had a stronger effect on sex hormone levels. However, genetic evidence did not support causality for the associations. The mechanisms underlying these associations household air pollution (HAP) from incomplete combustion of such fuels and occurrence of chronic diseases remained obscure. Recent years, extensive evidences from animal as well as human researches have suggested that progestogen and androgen hormones are involved in the development of diabetes, hypertension, and cardiovascular disease, which indicated that changes in serum progestogen and androgen hormones levels might play a role in these pathological mechanisms. However, limited evidence exists examining the effect of HAP from solid fuel use on serum sex hormone levels.