Researchers found that women who started smoking before the age of 13 were more likely to experience chronic severe menstrual cramps than non-smokers.
Menstrual cramps, also referred to as period pain or dysmenorrhea, affect around 91% of women throughout their reproductive life. Of these women, up to 29% experience severe menstrual cramps.
Although many women are able to carry on with their day-to-day lives during menstrual cramps, the condition can be debilitating in some cases. In the US, period pain is the most common cause of lost time from school and work for adolescent females and women in their 20s.
According to the research team, including Dr. Hong Ju of the University of Queensland in Australia, past studies investigating the link between smoking and severe menstrual cramps have produced mixed results.
As such, Dr. Ju and colleagues set out to examine this association in more detail, looking at how smoking may affect a woman's risk of menstrual cramps over time.
For their study, the team analyzed 9,067 young women who had been a part of the Australian Longitudinal Study on Women's Health (ALSWH) since 1996, when they were aged 18-23.
Between 2000 and 2012, the women were required to take part in a survey every 3-4 years that asked them how often they experienced severe menstrual cramps. They were also asked if they currently smoke, had ever smoked in the past, and if so, at what age they started smoking.
Smoking before the age of 13 may raise risk of chronic severe period pain by 60%
In 2000, 26% of women were current smokers, 14.3% were ex-smokers and 59% were non-smokers. Of the current and ex-smokers, 7.3% of women said they began smoking before the age of 13, while 13.5% took up the habit aged 14-15. Around 8% of women said they began smoking before they started having monthly periods.
Around 25% of women said they had menstrual cramps every month in the year 2000. The team found that 29% of smokers experienced menstrual cramps, compared with 23% of non-smokers.
At the end of the 12-year monitoring period, the researchers decided to split the women into one of four groups dependent on the severity and duration of their menstrual cramps.
The "normative" group - who had no or few menstrual cramps - was made up of 42% of women, while 11% of women who experienced an increase in period pain prevalence from 15% to almost 70% over the 12 years were put into the "late onset" group.
The "recovering" group - those who experienced a reduction in period pain prevalence from 40% to 10% - was comprised of 33% of the women, while 14% of women were put into the "chronic" group, whose period pain prevalence increased by 70-80%.
Results of the study revealed that current smokers who took up the habit before the age of 13 were 60% more likely to experience chronic severe menstrual cramps - pain that lasts longer than 2 days at a time - compared with women who had never smoked. This result remained even after accounting for other influential factors, such as weight and reproductive history.
Commenting on their findings, the researchers say:
"This study linked smoking, especially early initiation, with increased risk of dysmenorrhea over time. It addresses the immediate health effects of smoking, further strengthens the message that antismoking programs should target young women, particularly teenagers.
In addition, smoking cessation should be strongly encouraged as women may recover from dysmenorrhea after quitting smoking."
Although these findings are purely observational, the team does present some theories that could explain them. They point out that smoking can reduce blood flow in the arteries, which may cause pain. In addition, they say smoking before puberty could have a "stronger impact on the endocrine system controlling menstruation," which may influence menstrual cramp severity.
The researchers stress, however, that these hypotheses and other mechanisms that may mediate the relationship between smoking and menstrual cramps require further study.