Early Menopause Linked to Chemical Exposure in Women

February 04, 2015

Women who have the highest levels of endocrine-disrupting chemicals (EDCs) from a wide variety of common household and personal-care products enter menopause anywhere from 1.9 to 3.8 years earlier than those who have lower levels of EDC, a cross-sectional sample of US women is showing.

"Even menopause a few years earlier than usual could have a significant effect on bone health, on cardiovascular health, on memory and quality of life for women in general," senior author Dr Amber Cooper (Washington University, St Louis, Missouri) told Medscape Medical News.

"But I think the bigger question — and one that warrants further research — is what's happening at the other end of the ovarian health spectrum. Is the age at which we get pregnant shifting earlier as well, so there are other events on the spectrum that we need to address?"

In their analysis of women in the National Health and Nutrition Examination Survey (NHANES), published online January 28 in PLOS One, Dr Cooper and colleagues identified 15 EDCs that they say warrant closer evaluation "because of their persistence (long half-life) and potential detrimental effects on ovarian function" — nine polychlorinated biphenyls (PCBs), three pesticides, a furan, and two phthalates were significantly associated with earlier ages of menopause on at least one type of analysis, they report.

"The observed magnitudes of effect of these 15 chemicals...are larger than those previously documented for primary exposure to tobacco smoke," they state. Tobacco smoke has been shown in prior NHANES studies to be associated with 0.8 to 1.4 years of earlier-onset menopause.

Asked to comment on the study, Dr Andrea Gore (University of Texas, Austin), editor-in-chief of Endocrinology, said it is difficult to avoid exposure to some of these chemicals.

"In many cases, these chemicals were banned 40 years ago in the US, yet we know that they are very persistent in the environment, and if persistent chemicals were found in people's bodies in 2008 [the last year Dr Cooper's team analyzed], they are still being found in people's bodies in 2015," she told Medscape Medical News.

But she says women can help limit their exposure to EDCs by avoiding processed and packaged foods and beverages: "Eating fresh foods that don't undergo any processing in factories or foods that don't come into contact with packaging will help minimize the exposure," she suggested.

The subject of endocrine-disrupting chemicals is one of controversy: just last month, Europe's food safety watchdog said one chemical used to stiffen some plastic food containers, bisphenol A (BPA), poses no health risk to consumers of any age, including unborn children, at current levels of exposure. The US Food and Drug Administration (FDA) banned BPA from baby bottles in 2012 but said there was not enough evidence for a wider ban and has found the chemical safe at low levels.

Study Details

The current analysis included data on 31,575 females involved in the NHANES periods 1999–2000, 2001–2002, 2003–2004, 2005–2006, and 2007-2008. The researchers did not include data after this because it was not publicly available in its entirety.

Women were included in the primary analysis if they were over the age of 30 (n = 13,705), menopausal (n = 2159), and had been tested for EDCs (n = 1442). A secondary analysis looked at women 45 to 55 years old with any EDC measured (n = 2234).

An analysis of 111 EDCs was carried out, but the greatest focus was placed on 35 EDCs with long half-lives — including include phytoestrogens, PCBs, and dioxins — and the phthalates, known reproductive toxicants.

For their threshold analysis, investigators defined exposure to EDCs as values in the top decile of the distribution of these chemicals among all women assessed for chemical status regardless of their menopausal status.

Investigators also examined whether or not there was a dose-response relationship between EDC levels and age at menopause.

Nine of the 10 EDCs associated with a significantly earlier age at menopause in the threshold analysis were also statistically significant in one of the two dose-response analyses.

And in the secondary analysis in women between 45 and 55 years of age, 11 out of 15 EDCs identified in the primary analyses were again associated with a significantly higher risk of being menopausal, the researchers add.

The odds of being menopausal among women between the ages of 45 and 55 ranged from 1.3 to more than sixfold higher for each one-unit increase in the log EDC level.

"Our study demonstrates a clinically significant association between levels of persistent EDCs and age at menopause in a large cross-sectional representative sample of US women," the researchers conclude.

However, Dr Cooper cautioned, "This study is just one snapshot in time, and it shows only an association; it cannot prove causation because we did not follow women longitudinally over time."

Raising Awareness of the Issue

But she added: "My hope with this study was really just to raise awareness of this issue more than anything else.

"And while I think that awareness of these chemicals is slowly increasing, exposure to many of them is beyond our control, because they are in the soil, the water, and in the air, so they are ubiquitous and we can't really avoid them."

Dr Gore said certain groups are working to increase awareness of how people can try to reduce exposure to EDCs found in plastics, household items, and personal-care products.

"Menopause is not a disease; it's a natural process," she said.

"But when menopause happens early, your body is responding to these environmental exposures by terminating reproductive function earlier, so I think early menopause is a biomarker of chemical exposure, and these chemicals affect not only the reproductive system but other endocrine functions as well."

Dr Cooper and colleagues agree: "Earlier menopause can alter the quantity and quality of a woman's life and has profound implications for fertility, human reproduction, and our global society," they conclude.

The research was supported in part by the National Institutes of Health. The authors and Dr Gore have reported no relevant financial relationships.

PLOS One. Published online January 28, 2015. Article

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