Perimenarchal air pollution exposure and menstrual disorders

STUDY QUESTION: What is the association between perimenarchal exposure to total suspended particulate (TSP) in air, menstrual irregularity phenotypes and time to menstrual cycle regularity? SUMMARY ANSWER: Exposures to TSP during high school are associated with slightly increased odds of menstrual irregularity and longer time to regularity in high school and early adulthood. WHAT IS KNOWN ALREADY: The menstrual cycle is responsive to hormonal regulation. Particulate matter air pollution has demonstrated hormonal activity. However, it is not known if air pollution is associated with menstrual cycle regularity. STUDY DESIGN, SIZE, DURATION: Cross sectional study of 34 832 of the original 116 430 women (29.91%) enrolled in 1989 from the Nurses’ Health Study II (NHSII). The follow-up rate for this analytic sample was 97.76% at the 1991 survey. PARTICIPANTS/MATERIALS, SETTING, METHODS: Annual averages of TSP were available for each year of high school attendance. We created three case definitions including high school menstrual irregularity and androgen excess. The time to menstrual cycle regularity was reported by participants as