The Incidence of Fibromyalgia and Its Associated Comorbidities: A 
Population-Based Retrospective Cohort Study Based on International 
Classification of Diseases, 9th Revision Codes.

J Clin Rheumatol. 2006 Jun;12(3):124-128.

Weir, Peter T. MD [*]; Harlan, Gregory A. MD, MPH [+]; Nkoy, Flo L. MD, MS, 
MPH [+]; Jones, Spencer S. BS [*]; Hegmann, Kurt T. MD, MPH [++]; Gren, 
Lisa H. MSPH [*]; Lyon, Joseph L. MD, MPH [*]

 From the [*] Department of Family and Preventive Medicine, the [+] 
Department of Pediatrics, and the [++] Rocky Mountain Center for 
Occupational and Environmental Health, University of Utah, Salt Lake City, 
Utah.

PMID: 16755239


BACKGROUND: The epidemiology of fibromyalgia is poorly defined. The 
incidence of fibromyalgia has not been determined using a large population 
base. Previous studies based on prevalence data demonstrated that females 
are 7 times more likely to have fibromyalgia than males and that the peak 
age for females is during the childbearing years.

OBJECTIVE: We have calculated the incidence rate of fibromyalgia in a 
large, stable population and determined the strength of association between 
fibromyalgia and 7 comorbid conditions.

METHODS: We conducted a retrospective cohort study of a large, stable 
health insurance claims database (62,000 nationwide enrollees per year). 
Claims from 1997 to 2002 were examined using the International 
Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) 
codes to identify fibromyalgia cases (ICD code 729.1) and 7 predetermined 
comorbid conditions.

RESULTS: A total of 2595 incident cases of fibromyalgia were identified 
between 1997 and 2002. Age-adjusted incidence rates were 6.88 cases per 
1000 person-years for males and 11.28 cases per 1000 person-years for 
females. Females were 1.64 times (95% confidence interval = 1.59-1.69) more 
likely than males to have fibromyalgia. Patients with fibromyalgia were 
2.14 to 7.05 times more likely to have one or more of the following 
comorbid conditions: depression, anxiety, headache, irritable bowel 
syndrome, chronic fatigue syndrome, systemic lupus erythematosus, and 
rheumatoid arthritis.

CONCLUSION: Females are more likely to be diagnosed with fibromyalgia than 
males, although to a substantially smaller degree than previously reported, 
and there are strong associations for comorbid conditions that are commonly 
thought to be associated with fibromyalgia.