“The Pill CAN ease the agony of period pain: scientists confirm what millions of women already know,” the Daily Mail reported today. This headline is based on a study that found that use of the combined oral contraceptive pill (and, to a lesser extent, getting older and childbirth) was associated with slightly less severe period pain.
However, the media have missed the point that this study does not show that the pill reduces period pain. It simply shows that at two points in time, on average, women on the pill assessed their period pain as being slightly less than non-pill users did. It is possible that many other factors played a part in these women’s experience of pain. The study also relied on women self-reporting their pain through a postal questionnaire. Subjective experiences of pain vary and can be influenced by many factors, which means the results are less reliable.
The authors of this research – who advocate that contraceptive counselling sessions should outline the possible benefits of the pill for period pain – have links with the manufacturers of contraceptive pills. However, their study was not funded by pharmaceutical companies.
The pill is currently prescribed by many doctors as an ‘unlicensed’ treatment to reduce period pain, despite there being very little good evidence supporting this practice. The best available evidence (a systematic review of all trials for period pain without underlying causes) consisted of only a few trials but concluded that combined contraceptives with doses less than 35 micrograms were effective for treating period pain. Anyone studying this again should conduct a randomised trial not a survey.
Where did the story come from?
The study was carried out by researchers from Gothenburg University, Sweden. It was funded by the Gothenburg Medical Society and other funding bodies. The authors say they have participated in clinical trials and international advisory boards sponsored by various pharmaceutical companies and have also received lecture fees from industry. This is called a conflict of interest.
The research was published in the peer-reviewed journal Human Reproduction.
The Mail reported the study’s findings as the gospel truth – possibly influenced by a press release that said the study was ‘convincing evidence’ the pill helped with painful periods. The paper also claimed that combined oral contraceptive pill use relieved symptoms in one-third of young women, which is an overinterpretation of the study’s results.
The BBC was also uncritical, although its report did include previous research that found the evidence for pain improvement was limited. The BBC also pointed out that the pill is not licensed as a treatment for period pain by EU regulations.
What kind of research was this?
This was a cross-sectional study used to evaluate both combined oral contraceptives and the influence of age on the severity of period pain (which doctors call dysmenorrhoea). This type of study cannot be used to show that a particular treatment is effective. A randomised controlled trial would be needed for this.
The researchers point out that although combined oral contraceptives (COCs) are widely thought to reduce the severity of period pain, their effectiveness is based on few randomised trials and the quality of research has recently been questioned in reviews. This includes one from The Cochrane Collaboration (an organisation that conducts systematic reviews of evidence for treatments).
What did the research involve?
The researchers recruited random samples of women living in the city of Gothenburg, Sweden, who were aged 19 in 1981, 1991 and 2001. The three groups contained about 600 to 700 women each. The women were contacted by letter and asked to complete a questionnaire with 40 questions on their height, weight, reproductive history, pattern of menstruation, menstrual pain and contraceptive use.
The researchers assessed the women’s severity of menstrual pain using a scoring system (called verbal multidimensional or VMS), which graded pain as none, mild, moderate or severe. VMS also takes account of the effect of pain on women’s ability to do daily activities and whether they need painkillers. It uses a visual analogue scale in which women graded their degree of pain on a 10cm line that starts with ‘no pain at all’ and ends with ‘unbearable pain’.
The women who answered the questionnaire (91% of the first group, 82% of the second and 77% of the third) were contacted five years later and were asked to complete and return a second questionnaire asking the same questions. The questionnaire was completed and returned at both 19 and 24 years by 75% of the first cohort, 67% of the second and 59% of the third.
The researchers analysed the responses by looking to see if use of the pill was associated with less pain. They used several techniques including an analysis of the strength of any link found between the pain, pill use, increasing age or the severity of the pain reported. They accounted for factors that might affect results such as smoking and weight. Women who had had children or who were using certain types of contraceptives (progesterone only pill or an IUD intrauterine device) were excluded from one analysis because both these factors are thought to reduce pain.
What were the basic results?
The researchers found that the severity of period pain (dysmenorrhoea) was lower in pill users compared with non-users. They also found that increasing age was associated with less period pain to a lesser extent than pill use.
- pill use was associated with a reduction in pain of 0.3 units on the a verbal scoring system (assessing the pain as none, mild, moderate or severe) and 9mm on the visual analogue scale (VAS)
- increasing age was associated with a reduction in pain of 0.1 units after five years on the verbal score and 5mm after five years on the VAS
- childbirth was also associated with reduce pain severity, by 7mm on the VAS
- women from the third group reported a greater severity of period pain compared with the two earlier groups
How did the researchers interpret the results?
Use of the combined oral contraceptives reduced the severity of period pain, equivalent to ‘the transfer of every third woman one step down on the verbal scale’. The researchers argue that this equates to less pain for women using the pill, improved working ability and reduced need for painkillers. They argue that the possible benefits of COCs for relief of period pain should be included in contraceptive counselling.
This study does not show that the pill reduces period pain. All it shows is that at two points in time, overall, women on the pill self-assessed their period pain as being slightly less than non-pill users. It is possible that many other factors played a part in these women’s experience of pain. The study also relied on women self-reporting their pain in a postal questionnaire. Subjective experiences of pain vary and are influenced by many factors. This makes the results less reliable.
To find out if the pill reduced pain, the study compared each woman’s experience of pain and use of contraception at different ages, using each woman in the study as her own control. However, this is not considered a reliable way to measure the effectiveness of any treatment.
The pill is widely believed to reduce period pain by preventing the production of certain hormones. Anyone studying this again should aim to conduct a well-designed, randomised controlled trial to examine whether, and how far, the pill reduces the severity of period pain. They should also look at how its potential benefits and risks compare to other existing drugs, such as painkillers, or self-treatments, such as a hot water bottle or gentle exercise.