Incidence and predictors of secondary fibromyalgia in an early arthritis cohort.
OBJECTIVE
Secondary fibromyalgia (FM) is common among patients with inflammatory arthritis, but little is known about its incidence and the factors leading to its development. The authors examined the incidence of secondary FM in an early inflammatory arthritis cohort, and assessed the association between pain, inflammation, psychosocial variables and the clinical diagnosis of FM.


METHODS
Data from 1487 patients in the Canadian Early Arthritis Cohort, a prospective, observational Canadian cohort of early inflammatory arthritis patients were analysed. Diagnoses of FM were determined by rheumatologists. Incidence rates were calculated, and Cox regression models were used to determine HRs for FM risk.


RESULTS
The cumulative incidence rate was 6.77 (95% CI 5.19 to 8.64) per 100 person-years during the first 12 months after inflammatory arthritis diagnosis, and decreased to 3.58 (95% CI 1.86 to 6.17) per 100 person-years 12-24 months after arthritis diagnosis. Pain severity (HR 2.01, 95% CI 1.17 to 3.46) and poor mental health (HR 1.99, 95% CI 1.09 to 3.62) predicted FM risk. Citrullinated peptide positivity (HR 0.48, 95% CI 0.26 to 0.88) was associated with decreased FM risk. Serum inflammatory markers and swollen joint count were not significantly associated with FM risk.


CONCLUSIONS
The incidence of FM was from 3.58 to 6.77 cases per 100 person-years, and was highest during the first 12 months after diagnosis of inflammatory arthritis. Although inflammation was not associated with the clinical diagnosis of FM, pain severity and poor mental health were associated with the clinical diagnosis of FM. Seropositivity was inversely associated with the clinical diagnosis of FM.
Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. ylee9@partners.org
Yvonne C
YC
Lee
Bing
B
Lu
Gilles
G
Boire
Boulos Paul
BP
Haraoui
Carol A
CA
Hitchon
Janet E
JE
Pope
J Carter
JC
Thorne
Edward Clark
EC
Keystone
Daniel H
DH
Solomon
Vivian P
VP
Bykerk
D000328:Adult; D000368:Aged; D000906:Antibodies / Q000276:immunology; D001168:Arthritis / Q000453:epidemiology; D001172:Arthritis, Rheumatoid / Q000453:epidemiology*; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005356:Fibromyalgia / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D010147:Pain Measurement; D010456:Peptides, Cyclic / Q000276:immunology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index
D000906:Antibodies; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide