Objectives 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.
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Funding YCL is funded by the NIH (AR 057578). DHS receives salary support from the NIH (AR 055989). The CATCH study was designed and implemented by the investigators, and financially supported, initially, by Amgen Canada Inc. and Pfizer Canada Inc., via an unrestricted research grant. As of 2011, further support was provided by Hoffmann-La Roche Ltd., United Chemicals of Belgium (UCB) Canada Inc., Bristol-Myers Squibb Canada Co., Abbott Laboratories Ltd., and Janssen Biotech Inc. (a wholly owned subsidiary of Johnson & Johnson Inc.).
Competing interests YCL has stock in Merck, Novartis and Elan Corporation, and has a research grant from Forest. GB serves on the boards of Janssen, Amgen, BMS, Abbott, UCB, Pfizer. He receives grant support from Merck Canada, Novartis, Amgen, Warner-Chilcott, Janssen and Abbott, and develops educational presentations for AstraZeneca, Merck, Amgen, Novartis, Eli Lilly and Warner-Chilcott. BH serves on advisory boards for Abbott, Amgen, BMS, Pfizer, Roche and UCB. BH has a research grant from Institut de rheumatologie de Montreal (Amgen and Pfizer), and he receives payment for lectures for Amgen, Pfizer, Roche and Abbott, and for educational presentations for BMS. CAH receives grant funding from UCB and AstraZeneca. JEP is on the boards of, serves as a consultant for, and/or receives grant funding from Amgen, Abbott, UCB, BMS, Roche, Johnson and Johnson, Pfizer, Actelion, AstraZeneca and Glaxo Smith Kline. JEP also receives payment for lectures for Amgen, Actelion, BMS, Roche, Johnson and Johnson and Pfizer. JCT is on the boards of Amgen, Pfizer, Abbott, Jannsen, Roche, UCB and BMS. ECK is a consultant for Abbott, AstraZeneca, Biotest, BMS, Centocor, Roche, Genentech, Merck, Nycomed, Pfizer and UCB. ECK has grant funding from Amgen, Abbott, AstraZeneca, BMS, Centocor, Roche, Genzyme, Merck, Novartis, Pfizer and UCB. ECK receives payment for lectures for Abbott, BMS, Roche, Merck, Pfizer, UCB, Amgen and Janssen. DHS receives research support from Abbott, Amgen and Lilly. VPB is a consultant for Pfizer, BMS, Roche, UCB, Abbott and Kalabios. VPB receives payment for lectures for UCB. The CATCH study was designed and implemented by the investigators and financially supported, initially, by Amgen Canada Inc. and Pfizer Canada Inc. via an unrestricted research grant. As of 2011, further support was provided by Hoffmann-La Roche Ltd., United Chemicals of Belgium (UCB) Canada Inc., Bristol-Myers Squibb Canada Co., Abbott Laboratories Ltd., and Janssen Biotech Inc. (a wholly owned subsidiary of Johnson & Johnson Inc.).
Ethics approval Research ethics boards representing all individual investigative sites.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data are available upon request made to the corresponding author, with approval from the CATCH investigators.