Thursday, March 24, 2011

Chronic Widespread Pain. Is It an Epidemic?

The term Chronic Widespread Pain Syndrome (CWPS) is synonymous with fibromyalgia (FM). It is characterized by the finding of pain on palpation at 11 or more of 18 specific sites, although the diagnosis of FM apparently can be made with fewer sites involved.

A recent paper, “Road traffic accidents, but not other physically traumatic events, predict the onset of chronic widespread pain: results from the EpiFunD Study,” which was a survey of residents of three different areas in Northwest England, noted some remarkable findings. The publisher was kind enough to provide a full text copy of the paper. Some 17% of 6244 subjects had CWPS at baseline. They were excluded from further study. More than half of the remaining subjects were lost to follow-up. Even more remarkable is that over the four years of the research, 11.6% of the 2069 subjects who did respond to a repeat survey developed CWPS. The authors found that involvement in a traffic accident might lead to an increased incidence of CWPS.

The most remarkable finding was not addressed in the paper. If one does the math for a rate of developing CWPS of 11.6% over four years, one can see by the figure below that at about 22 years from now, half of the study population of 2069 subjects will have developed CWPS. The number of subjects appears on the y-axis and years is on the x-axis. The red arrow at 22 years points to the 1000 subject line.

The authors mentioned some of the limitations of the study in their discussion. The fact that fewer than 50% of those entered into the study were available at its conclusion and the self-reporting of pain and history of trauma were acknowledged as weaknesses.

According to the study's lead author, Dr. Gareth T Jones, whether the subjects with CWPS were being treated with pain medication or being followed by a physician could not be determined. In an email Dr. Jones said, "Individuals with chronic widespread pain are characterized as being high health service users, with multiple tests/investigations, and, yes, medication use (and complementary medicine use) is common."

He agreed that the baseline prevalence of 17% was high but pointed out, "Population studies have fairly consistently shown a prevalence [of chronic pain] of around 12-13%."

Also, there is the matter of potential secondary gain if a traffic accident victim is found to have CWPS. Dr. Jones stated: "Clearly, for people who are reporting a claim then there may be greater financial benefit if that pain is (a) more persistent; and (b) more severe and/or disabling. Of course, that's not to say that the pain isn't genuine. it may be that a long legal process will focus the mind on one's problems, and that this focused attention may genuinely contribute to the exacerbation of symptoms."

When asked about what seems to be a projected epidemic of CWPS in Northwest England Dr. Jones had these comments: "It's not quite as simple as that, but yes I agree, the numbers stack up fairly quickly. People move in and out of different pain states from no pain to regional pain, to widespread pain, to chronic widespread pain and also back in the other direction. Studies have shown, however, that it is rare for someone with chronic widespread pain to no pain at all in a subsequent survey."

What will become of these subjects over the years remains to be seen. Perhaps future studies will help clarify the issues raised.

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