Women who smoke cigarettes may be at higher risk for menstrual pain, according to a new Australian study.
Compared to non-smokers, smokers in the study were more likely to suffer from severe menstrual pain and to experience a worsening of pain as the number of cigarettes they smoked per day increased.
Exactly how smoking cigarettes might increase menstrual pain is not entirely clear, but it may happen via a decrease in the amount of oxygen available to the uterus, Dr. Jennifer Leighdon Wu, an obstetrician/gynaecologist at Lenox Hill Hospital in New York City, told Reuters Health in a phone interview.
"We know that smoking causes vasoconstriction, or constriction of the blood vessels," said Wu, who wasn't involved in the new study. "When this happens with the uterus, it can cause pain."
Dysmenorrhoea among smokers
The study, published in the journal Tobacco Control, tracked 9 067 women for an average of 13 years. At the start of the research, the women were between the ages of 18 and 23. About 25 percent reported experiencing dysmenorrhoea, or painful periods, and approximately 25 percent were current smokers.
During the course of the study, about 14 percent of the women had painful periods 70 to 80 percent of the time, which the researchers considered to be "chronic" dysmenorrhoea.
Compared with women who had never smoked, the risk of having chronically painful periods during the course of the study was 33 percent higher for former smokers and 41 percent higher for current smokers – even after accounting for social, lifestyle, and reproductive factors that might contribute to dysmenorrhoea.
Read: Do you think women should get paid menstrual leave?
The researchers also found that the earlier women started to smoke, the higher their risk of chronically painful periods. Specifically, the risk was 59 percent higher for women who started to smoke before age 13, and 50 percent higher for those who took up cigarettes at age 14 or 15.
The results may provide an incentive for young women to abstain from smoking, study leader Dr. Hong Ju of the University of Queensland told Reuters Health by email.
Abstain from smoking
"This study conveys some important messages that smoking may predispose women to repeated, distressing period pain immediately after menstruation and throughout their reproductive life, thus providing greater incentive for young women to abstain from smoking," Ju and colleagues wrote in their report.
While the study involved young Australian women, the results "can be generalised to young women from other countries with similar characteristics," Ju said.
Menstrual pain affects up to 91 percent of women of reproductive age, the researchers say. Some 2 to 29 percent of the women report severe pain, and may miss work or school as a result.
"There is a very real economic loss due to dysmenorrhoea. Women can lose a day or two of work a month, which translates into a lot of lost work force," Wu said.
Read:Viagra may ease period pain
As for why women who start smoking while very young tend to have worse menstrual pain, the cause could be hormonal, she said.
"There are a lot of hormones that come into play at the time of puberty, and taking up smoking before the age of 13 may affect that hormonal axis," Wu said. "This could be why these young girls have a lot of pain when they get their period."
Observational studies such as this one can't prove that smoking causes menstrual pain, however. And as for whether quitting smoking would ease menstrual pain, the jury is still out.
"We performed a preliminary analysis on the data and it shows that women who gave up smoking were more likely to recover from menstrual pain," Ju said. "However, more research is needed to confirm the hypothesis."