A Pilot Study of Reproductive Health and Anti-Müllerian Hormone Levels Among Female Firefighters

Abstract

Background: Female firefighters may be highly exposed to chemicals through their job, which may negatively impact their reproductive health. Anti-müllerian hormone (AMH) is a clinical marker of ovarian reserve and may be influenced by environmental and occupational exposures but few studies have measured AMH on a population-level. Therefore, the objective of this study was to investigate whether AMH levels differed in female firefighters compared to comparison women and to investigate whether there is a dose-dependent relationship between years of firefighting and AMH levels among female firefighters. Methods: Firefighters, recruited from a pre-existing female firefighter cohort, completed a cross-sectional survey regarding their occupational history and were asked to recruit a non-firefighter friend or relative. All participants completed a questionnaire and provided a dried blood spot (DBS) sample where we measured their AMH level. For the analysis, AMH was log-transformed. Linear regression was used to assess the relationship between firefighting status and log transformed AMH levels. Models were adjusted for age, age2, and current hormonal contraceptive use. Percent differences and 95% confidence intervals (CIs) in AMH between exposure groups were calculated from the βs using ([exp(β) −1] *100) and presented with corresponding 95% CIs. Models were stratified by body mass index (BMI) to investigate possible effect modification. Among firefighters, we also investigated the influence of firefighting-related exposures. Sensitivity analyses excluded women with confirmed or suspected Polycystic ovarian syndrome (PCOS) (AMH 10ng/ml). Results: In our sample, firefighters (n=86) and non-firefighters (n=54) had similar mean age and BMI. Firefighters were more likely to report a history of infertility (18.6%) compared to non-firefighters (5.6%). Firefighters worked mainly as firefighters, drivers, or operators (41.9%). Over half of firefighters reported poor fit of at least part of their personal protective equipment (PPE), with 23.3% of firefighters reporting poor fit of their self-contained breathing apparatus (SCBA). Firefighters had a lower mean AMH compared to non-firefighters (3.35 ng/mL vs. 4.36 ng/mL) (-38.39% (95% CI: -61.53, -1.33)), but this association attenuated after adjustment for age, age2, and current hormonal contraceptive use (-25.58% (95% CI: -49.97, 10.71)). Differences in the relationship between firefighter history and AMH were observed by BMI status. We observed no difference in AMH among normal BMI participants, however among participants with obese and overweight BMI, firefighters had a lower mean AMH than non-firefighters (Overweight: 2.85 ng/mL vs. 4.64 ng/mL; Obese: 3.63 ng/mL vs. 6.30 ng/mL) (Table 4). Among firefighters, for every five years in the fire service, AMH levels decreased by 40% (-40.32% (95% CI: -54.01, -22.55), but this difference attenuated after adjustment (1.16% (95% CI: -25.50, 37.37)). Conclusion: Our results suggest that there may be an association between exposures related to working as a firefighter and a biologic marker of reproductive health, AMH. However, we were not adequately powered to detect statistically significant differences among female firefighters after adjustment. The proportion of firefighters with a history of infertility indicates a need for future research on the topic.