Sulfur dioxide exposure and other factors affecting age at natural menopause in the Jinchuan cohort

Abstract

Objective To describe the associations between occupational exposures and age at natural menopause in the Jinchuan cohort.

Methods The Jinchuan cohort consists of all current or retired workers of the Jinchuan Nonferrous Metals Corporation (JNMC) in Jinchang, Gansu, China. Our final study population consisted of 3167 postmenopausal women. The data used for this study were derived from the epidemiological survey and were self-reported. Age at natural menopause (ANM) was defined as the age at the last period prior to 12 months of amenorrhea in women who experienced natural menopause. ANM was related to five commonly reported occupational exposures using bivariate and multivariate Cox proportional hazards regressions.

Results Blue-collar workers have significantly earlier mean ANM (49.0 years) than white-collar workers (49.5 years). Sulfur dioxide exposure was found to be associated with earlier mean ANM in blue-collar workers. After stratifying both blue-collar workers and white-collar workers further by exposure time for each of the exposures, blue-collar workers exposed to sulfur dioxide for 21–25 years had the earliest mean ANM (47.8 years) of any level of any exposure in this study.

Conclusion This paper is significant because it is the first report of an association between sulfur dioxide and menopause, and one of few papers to look at the determinants of ANM in an occupational cohort. Blue-collar workers had earlier mean ANM than white-collar workers. Blue-collar workers are more exposed to sulfur dioxide and other occupational exposures than white-collar workers, and blue-collar workers who are more exposed to sulfur dioxide have earlier menopause. Sulfur dioxide may be part of the reason that blue-collar workers experience earlier menopause than white-collar workers.

Key words::

• SULFUR DIOXIDE
• AGE AT NATURAL MENOPAUSE
• CHINESE WOMEN

ACKNOWLEDGEMENTS

We would like to thank Longfei Liu for his comments and support, and Hongquan Pu and the Jinchuan Worker's Hospital for their collaboration on the Jinchuan cohort. We also thank the team of graduate students and professors at the Lanzhou University School of Public Health Department of Biostatistics and Epidemiology for efforts in the collection and management of epidemiological data, and the Jinchuan Nonferrous Metals Corporation for their cooperation.

Conflict of interest The data collection was funded in part by the Jinchuan Nonferrous Metals Corporation (JNMC) but JNMC had no part in the data analysis for this study or the drafting of this paper, nor did they review the results before submission. The authors alone are responsible for the content and writing of the paper.

Source of funding This study was supported by Lanzhou University, Yale University, the Jinchuan Worker's Hospital, and the Fulbright Foundation, and funded by the Project of Science and Technology of the Jinchuan Nonferrous Metals Corporation (2011–2014).