Air Pollutants Increase Risk for Dysmenorrhea

Dysmenorrhea presents frequent severe and painful cramps during menstruation from abnormal contractions of the uterus for up to 16-91% of girls and women of reproductive age, of whom 2%-29% have symptoms severe enough to restrict their daily activity. Air pollution may be a risk factor, according to researchers from China Medical University Hospital in Taiwan. The found that long-term exposure to air pollutants such as nitrogen and carbon oxides and fine particulate matter raises the risk of developing dysmenorrhea.

Dysmenorrhea

Dysmenorrhea can be due to hormonal imbalances or to underlying gynecological conditions such as endometriosis, pelvic inflammatory disease, ectopic pregnancy, or tumors in the pelvic cavity. Symptoms are often life-long: they include cramps and pain in the lower abdomen, pain in the lower back and legs, nausea and vomiting, diarrhea, fainting, weakness, fatigue, and headaches. The socioeconomic impact can be great as it impacts quality of life and ability to attend school and work and participate in active lifestyles. The cause is largely unknown, and symptoms may be managed with anti-inflammatory drugs and hormonal contraceptives.

The study sample exclusively included women and girls without any recorded history of dysmenorrhea before 2000. The authors looked for a long-term association between the risk of dysmenorrhea and air quality, in particular the mean exposure over the years to air pollutants – nitrogen oxide (NOx), nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), and particles smaller than 2.5 μm in diameter (‘PM2.5’) – obtained from the ‘Taiwan Air Quality Monitoring Database’ (TAQMD) of the Environmental Protection Agency.

Based on long-term data on air quality and public health from national databases, they show that the risk to develop dysmenorrhea over a period of 13 years (2000-2013) was up to 33 times higher among Taiwanese women and girls who lived in areas with the highest levels of air pollutants compared to their peers exposed to lower levels of pollutants. These results were recently published in the open access journal Frontiers in Public Health.

The researchers categorized air pollution into one-of-four categories, which was based on seven urbanization levels on the basis of population density (people/km2); the proportion of residents with higher education, and who work in agriculture; and the number of physicians per 100,000 people in each area.

They found that from 2000- to 2013, 4.2% of women and girls in the studied sample were diagnosed with dysmenorrhea for the first time. As was expected from previous studies, younger women, women of lower incomes, and living in more urbanized areas tended to have a higher risk of developing dysmenorrhea over the study period.

But importantly, the ‘hazard ratio’ (that is, the age- and year-specific risk) of developing dysmenorrhea increased by 16.7 to 33.1 fold for women and girls from the 25% of areas with the highest yearly exposure to air pollutants, compared to those from the 25% of areas with the lowest exposure.

Levels of NOx, NO, NO2, CO, and (PM2.5) each contributed separately to the increased risk, but the greatest individual effect was from long-term exposure to high (PM2.5). More specifically, they found:

  • After controlling for potential confounding factors, Q4 air pollutant level exposure had higher risk of dysmenorrhea significantly compared with Q1 level of air pollutants.
  • The mean concentrations of yearly air pollutants were 28.2 (±12.6) ppb for nitric oxides (NOx), 8.91 (±7.93) ppb for nitric oxide (NO), 19.3 (±5.49) ppb for nitrogen dioxide (NO2), 0.54 (±0.18) ppm for carbon monoxide (CO), and 31.8 (±6.80) μg/m3 for PM2.5. In total, 12,514 individuals developed dysmenorrhea during the 12-year follow-up.
  • Participants exposed to the Q4 level air pollutant including NOx, NO, NO2, PM2.5, and CO mostly lived in the level 1 urbanization area.

Air Pollutants are an Important New Risk Factor for Dysmenorrhea

“Research has already shown that women who smoke or drink alcohol during their periods, or who are overweight, or have their first period very young, run a greater risk of dysmenorrhea. Women who have never been pregnant are likewise known to be at greater risk. But here we demonstrate for the first time another important risk factor for developing dysmenorrhea: air quality, in particular long-term exposure to pollution,” says one of the authors, Prof Chung Y. Hsu at the College of Medicine, China Medical University, Taichung, Taiwan. “We don’t yet know the underlying mechanism, but emotional stress in women exposed to air pollutants, or higher average levels of the hormone-like prostaglandins in their body, might be part of the answer.”

Conclusion/ “Our results study demonstrate the major impact of the quality of air on human health in general, here specifically on the risk of dysmenorrhea in women and girls. This is a clear illustration of the need to for actions by governmental agencies and citizens to reduce air pollution, in order to improve human health,” concludes Prof Hsu.

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Source: Lin SY, Yang YC, Lin CC, Chang CY, Hsu WH, Wang IK, Lin CD, Hsu CY, Kao CH. Increased Incidence of Dysmenorrhea in Women Exposed to Higher Concentrations of NO, NO2, NOx, CO, and PM2.5: A Nationwide Population-Based Study. Front Public Health. 2021 Jun 17;9:682341. doi: 10.3389/fpubh.2021.682341