Can the risk of lung cancer mortality be predicted by the sex ratio at birth?

Over the past 5 decades, sex ratio at birth (SRB) has declined significantly. It is noteworthy that SRBs may vary considerably across geographical regions and time periods, making them a valuable indicator of general population health and a potential signal of adverse environmental conditions. Long-term exposure to fine particulate matter (PM_2.5) was associated with higher SRBs as well as increased lung cancer risk. It is unclear whether the relationship between these two parameters is coincidental or whether elevated SRBs in PM_2.5 air-polluted areas might serve as a predictor of lung cancer risk. The aim of this study was to examine the possible association between SRBs and the likelihood of death attributed to lung cancer. In order to achieve this aim, studies were conducted, in which PM_2.5 levels, number of SRBs, and standardized mortality ratio (SMR) for lung cancer were determined for 66 municipalities in Taiwan from 2010 to 2023. SRBs were found to display a non-significant positive association with lung cancer mortality risk in women. The relative risks (RRs) in the second, third, and fourth quartiles of SRB were 1.019 (95% CI = 0.961-1.080), 1.031 (95% CI = 0.973-1.093), and 1.028 (95% CI = 0.970-1.090), respectively, compared with the lowest quartile of SRB. For men, they were 0.992 (95% CI = 0.946-1.040), 0.996 (95% CI = 0.950-1.045), and 1.03 (95% CI = 0.982-1.081). Data suggested that routine monitoring of SRBs may not be sufficiently sensitive to serve as a reliable screening measure for detection of population-level health risk based upon lung cancer findings, particularly in areas with high levels of PM_2.5 air pollution.