Patients with FMS often were seen for other medical problems, including back pain, cervical pain, painful neuropathic disorders, respiratory infections, hypertension and sleep disorders; they were also commonly seen for mood disorders, including depression and anxiety. Almost one-half of FMS patients had encounters with diagnoses of ‘symptoms, signs and ill-defined conditions’, including headache, abdominal pain, chest pain, fatigue and gastric-related symptoms. Without exception, the prevalence of these medical and psychiatric comorbidities was significantly higher among FMS patients than among age- and sex-matched patients without diagnoses of FMS.
Fibromyalgia syndrome is difficult to diagnose. In fact, some clinicians believe that FMS does not truly exist, and that resolution of FMS symptoms will result from proper treatment of all other, better-established conditions. Unfortunately, it is beyond the scope of our study to ascertain whether or not patients actually had FMS (the database does not contain patients’ medical records), or whether FMS is in fact an actual disease. However, we note that in addition to the higher frequency with which other conditions were noted among FMS patients, all such patients in our study also had at least one encounter for the treatment of FMS in each consecutive year of a 3-year period. This finding is perhaps suggestive that the clinicians of these patients were not satisfied that these conditions fully explained their symptoms.
It is important to note that these differences in the prevalence of various medical and psychiatric comorbidities are not necessarily suggestive of an aetiological link between these other conditions and FMS. Various possible explanations exist for this finding. For one, as FMS is characterized by widespread pain, tenderness and fatigue, patients with this condition may present more frequently to their medical providers than would otherwise be the case. More frequent visits may lead to opportunistic case finding and hence a higher prevalence of diagnosed medical and psychiatric comorbidities. Another possible explanation is the difficulty in making a diagnosis of FMS; patients might receive a variety of other diagnoses as various diseases and conditions are considered as possible explanations for the overlapping symptoms with which patients present.
During the year of study, FMS patients were nearly twice as likely as those in the comparison group to have received pain-related medications, and they were approximately fivefold more likely to have received multiple pain-related medications (primarily, antidepressants and opioids); use of non-pain-related medications was also higher. Given their higher levels of comorbidities and use of medications, it is not surprising that levels of utilization of healthcare services were much greater among FMS patients than patients in the comparison group; compared with the latter, the former averaged four times as many doctor office visits, twice as many other outpatient visits and four times more emergency room visits during the 12-month period of study. Mean healthcare costs were nearly three times higher among FMS patients vs. comparison patients. Our findings therefore indicate that patients with FMS are generally in poorer health and have greater levels of healthcare utilization and cost than patients of similar age and sex without this condition.
In epidemiological studies, which generally require patients to meet ACR criteria for FMS, women have constituted between 86% and 95% of study samples (1
). In our study, the number was only 75%. However, the proportion of women in studies such as ours, which used FMS diagnoses on health insurance claims, was 61–81%– consistent with the 75% reported in our study (21
Our study has several limitations. First and most important is our case-selection algorithm. Given the difficulty in making a correct diagnosis of FMS, it is likely that some patients who in fact do not have FMS receive a diagnosis of the disease on at least one occasion. To increase the specificity, we required that all patients in our sample have at least one encounter with a diagnosis of FMS in each of three consecutive years. One consequence of this decision is that we may have selected a cohort of FMS patients with relatively high levels of utilization. In the database, a total of 253,556 patients (6.8% of all patients in the database) had at least one claim with a diagnosis of FMS in any one year of the 3-year period that was used to identify FMS patients; 71,549 (1.9%) had claims with diagnoses of FMS in 2 years of the 3-year period. While it is unlikely that all 253,556 of these patients had FMS, it is entirely probably that our identified sample of 33, 176 patients is an underestimate of the total number of FMS patients in the database during this period of time. Accordingly, the generalizability of our findings to the population of FMS patients as a whole is unknown.
Second, information on medication use in healthcare claims databases is limited to prescription drugs, and specifically to prescriptions that are filled at outpatient (i.e. retail) pharmacies. Thus, to the extent that patients with FMS self-medicate with over-the-counter medications, we would have underestimated their total use of medications. We also do not know whether FMS patients in our study received pain-related medications for the treatment of FMS or for pain associated with other conditions (e.g. arthritis). In addition, as some pain-related medications are also used to treat conditions that are not commonly considered painful (e.g. AEDs in seizure disorders, antidepressants in depression), it would be incorrect to infer that all use of such agents was necessarily for the treatment of FMS pain. Because pharmacy records do not contain information on diagnosis, the extent to which pain-related medications were actually prescribed for the treatment of FMS is unknown. We note further that the database records only whether or not a prescription for a particular medication was filled; not how much, if any, the patient actually took.
Finally, we were limited to examining healthcare costs only. FMS is also associated with disability and may negatively impact productivity. One previous estimate, based on 4699 persons with at least one claim with a diagnosis of FMS employed by a US Fortune 100 manufacturer, estimated that FMS was associated with approximately $1552 (1998 dollars) in indirect costs (21
). Another estimate, based on 180 women identified by rheumatologists as having FMS using ACR criteria, estimated the 6-month impact of FMS on indirect costs [including market and non-market (i.e. household) work] to be $4335 (2001 dollars) (20
). Accordingly, our estimate likely understates the total economic burden of FMS.
In conclusion, our findings suggest that patients with FMS have strikingly high levels of comorbidities, and high levels of healthcare utilization and costs. Effective new treatments for FMS may lead to reductions in utilization and costs to the extent that these high levels are attributable to the disease.