Earlier Menopause Linked to Exposure to Endocrine Disrupting Chemicals

Commentary by: Amber Cooper, MD and Sarah S. Knox, PhD

Women with high levels of endocrine-disrupting chemicals experienced menopause 2 to 4 years earlier than women with lower levels of these chemicals, according to a cross-sectional study using data from using the National Health and Nutrition Examination Survey (NHANES). The findings were published in PLoS ONE.

“Earlier menopause can alter the quality of a woman’s life and has profound implications for fertility, health, and our society,” said senior author Amber Cooper, MD, Assistant Professor of Obstetrics and Gynecology at Washington University School of Medicine in St. Louis. “Understanding how the environment affects health is complex. This study doesn’t prove causation, but the associations raise a red flag and support the need for future research,” Dr. Cooper said.

“Many chemicals used in our everyday lives, such as pesticides, coolant fluids, plasticizers and flame retardants, disrupt the endocrine system, showing an inverse association with age of menopause,” commented Sarah S. Knox, PhD, who is a Professor of Epidemiology at West Virginia University School of Public Health and in Morgantown, WV. “The results of this study add further support to animal studies showing endocrine-disrupting effects of these chemicals,” Dr. Knox said.

Cross-Sectional, Nationally Representative Survey
The study included data from 31,575 women enrolled in the NHANES between 1999 and 2008. Of this group, 13,705 were older than 30 years of age; 2,159 were menopausal, and 1,442 were menopausal and underwent measurement for endocrine-disrupting chemicals. None of the women in this study were currently pregnant, breastfeeding, or using hormonal contraception, and none had a history of oophorectomy or hysterectomy.

The researchers examined data on blood and urine levels of 111 chemicals that are known endocrine-disrupting chemicals or that have a half life of more than 1 year. The primary outcome measure was age at last menstrual period in menopausal women.

15 Chemicals Linked to Early Menopause
As shown in the Table, the researchers identified 15 chemicals that were linked with earlier age at onset of menopause in either a threshold analysis or dose-response analysis. These included 9 polychlorinated biphenyls (PCBs, coolants), 3 pesticides, 2 phthalates (found in plastics, common household items, pharmaceuticals and personal care products), and 1 furan (eg, byproduct of industrial herbicide production).

Table. Association Between Exposure to Pervasive Endocrine-Disrupting Chemicals and Earlier Age of Menopause in Threshold and Dose-Response Analyses1

In the threshold analysis, women with the highest levels of these 15 chemicals (>90th percentile) had a self-reported onset of menopause that was 1.9 to 3.8 years earlier than those not in the top percentile. Evidence of a dose-response relationship was found in 14 of the 15 chemicals, suggesting that increasing levels of exposure to these chemicals may affect ovarian function, the authors noted.

“Many of these chemical exposures are beyond our control because they are in the soil, water and air,” Dr. Cooper said. “But we can educate ourselves about our day-to-day chemical exposures and become more aware of the plastics and other household products we use,” she said.

A study by Dr. Knox and colleagues reported a significant inverse association between perfluorooctane sulfonate (PFOS) and serum estradiol in perimenopausal and menopausal age groups. It also reported that the odds of having experienced menopause after adjusting for relevant covariates, was significant for both perfluorooctanoate (PFOA) and PFOS, Dr. Knox said.

“We believe that our study is important since it included a large cohort of 25,957 women.  However, our study data did not have exact age of menopause, which this study did,” Dr. Knox said. “This study also tested a larger number of endocrine disrupters,” she added.

To reduce health risks from these chemicals, Dr. Knox suggested avoiding flame retardant clothing, especially in children. “Do not microwave food in plastic containers or in cardboard food containers (they are lined with surfactants). Whenever feasible, buy organic vegetables to avoid pesticide residues, which do not disappear by rinsing in cold water,” Dr. Knox said.

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