Research shows air pollutants increase risk of dysmenorrhea

Long-term exposure to air pollutants such as nitrogen and carbon oxides and fine particulate matter greatly raises the risk of developing dysmenorrhea, according to new research published in the journal Frontiers in Public Health.

Dysmenorrhea, frequent severe and painful cramps during menstruation from abnormal contractions of the uterus, is the most common of all gynecological disorders. It affects between 16-91 percent of girls and women of reproductive age, of whom 2-29 percent have symptoms severe enough to restrict their daily activity, the researchers said.

According to the researchers, 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, and can include cramps and pain in the lower abdomen, pain in the lower back and legs, nausea and vomiting, diarrhea, fainting, weakness, fatigue, and headaches.

In addition to reducing quality of life, dysmenorrhea also has a major socioeconomic impact, as females with dysmenorrhea may be temporarily unable to work, attend school, or engage in leisure activities. Dysmenorrhea has no known cure, but its symptoms are often managed with antiinflammatory drugs and hormonal contraceptives.

The authors studied de-identified health measures from a total of 296,078 women and girls, approximately 1.3 percent of the total population between 16-55 years old. These data came from Taiwan's Longitudinal Health Insurance Database, a representative subsample from Taiwan's nation-wide health insurance database starting in 2000.

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, including nitrogen oxide (NO_x), 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.

The researchers found that from 2000 to 2013, 4.2 percent 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.

Further, the hazard ratio or the age- and year-specific risk of developing dysmenorrhea increased by 16.7 to 33.1-fold for women and girls from the 25 percent of areas with the highest yearly exposure to air pollutants, compared to those from the 25 percent of areas with the lowest exposure. Additionally, NO_x, NO, NO₂, CO, and PM2.5 levels each contributed separately to the increased risk, but the greatest individual effect was from long-term exposure to high PM2.5.

The researchers said they results study demonstrate the impact of the quality of air on human health, as well as the need to for actions by governmental agencies and citizens to reduce air pollution to improve human health.