Prevalence of Fibromyalgia: A Population‐Based Study in Olmsted County, Minnesota, Utilizing the Rochester Epidemiology Project

TLDR: To estimate and compare the prevalence of fibromyalgia by 2 different methods in Olmsted County, Minnesota, it is necessary to establish a baseline for each method to establish an apples-to- apples comparison.

Abstract: Fibromyalgia (FM) is a complex illness to diagnose and treat, with symptoms that may be part of, or overlap with other diseases or syndromes. It is also a costly public health problem. Medical costs related to health care utilization and pain-related medications for patients with FM are substantially higher than those for patients without FM (1–4). Therefore, evaluating the prevalence of FM has both clinical and economic relevance. Recognition of FM may not always be straightforward, because FM symptoms may be part of or overlap with other diseases or syndromes. Using the original 1990 American College of Rheumatology (ACR) criteria, Wolfe et al estimated that the prevalence of FM in the US general population is 2% (3.4% in women vs 0.5% in men) (5). Similarly, White et al (6), reporting on the London Fibromyalgia Epidemiology Study in Ontario, Canada, estimated the prevalence of FM at 3.3% (4.9% in women vs 1.6% in men), and Branco et al (7) reported on a multinational study of the prevalence of FM in 5 European countries, estimating it at 4.7%. A separate study, using a method similar to that of the ACR diagnostic criteria estimated the prevalence in Germany at 3.8%, with similar rates in men and women, (8). These differing estimates may reflect differences in study populations, study designs, and measurements. In 2010, the ACR published diagnostic criteria for FM that encompass the chronic widespread pain, fatigue, unrefreshing sleep, cognition, and somatic symptoms considered the hallmarks of this condition (9). These criteria were later modified to allow their use in epidemiologic and survey studies, without the requirement for an examiner to perform a tender point examination (10). The modification involved asking patients to report both pain and tenderness for the widespread pain index, in comparison to the ACR 2010 diagnostic criteria that only asked health care providers to determine areas of pain. Additionally, 3 representative items substituted for the comprehensive list of somatic symptoms that composed the ACR 2010 symptom severity score: 1) the presence or absence of headaches; 2) pain or cramps in the lower abdomen; and 3) depression in the past 6 months. Similar to the 2010 clinical criteria for FM, the modified criteria included a widespread pain index score of ≥7 and a symptom severity score of ≥5. Alternatively, participants are defined as having FM if the widespread pain index is 3 to 6 or the symptom severity score is ≥9. Additionally, symptoms must have been present at a similar level for at least 3 months. Routine use of these criteria in epidemiologic research may improve comparability of FM prevalence in different populations. Our primary objective in this study was to estimate the prevalence of FM in a defined population in 2 different ways. To accomplish this objective, we first estimated the prevalence of diagnosed FM in clinical practice in Olmsted County, Minnesota, using community medical records. We then surveyed a random sample of the population of Olmsted County using the modified 2010 ACR criteria to estimate the percentage of responders who fulfilled criteria.