Fibromyalgia, the classic non-inflammatory pain syndrome, has been associated with chronic inflammatory makers which are linked with increased morbidity and mortality. We tested the primary hypothesis that patients with fibromyalgia undergoing hospital procedures have a high risk of cardiovascular complications. Our secondary goals were to evaluate the association of fibromyalgia with: (i) in-hospital thromboembolic events, (ii) in-hospital mortality, and (iii) in-hospital microvascular complications.
We obtained 21.78 million discharge records from 2009 to 2010 from the US Agency for Healthcare Research and Quality censuses across the seven states. We matched fibromyalgia records and compared records with controls based on age, gender, state of discharge, principal procedure, and a propensity score developed from the set of diagnosis-related predictors. A multivariable logistic regression was used to compare matched fibromyalgia patients and controls on the primary and secondary outcomes.
We matched 89 589 pairs for a total sample size of 179 178 discharge records. The adjusted odds ratio for in-hospital cardiovascular complications was 1.04 [99% confidence interval (CI): 0.90-1.19, P=0.51], for thromboembolic events was 1.03 (99% CI: 0.93-1.15, P=0.46), for in-hospital mortality was 0.81 (99% CI: 0.73-0.89, P<0.001), and for microvascular complications was 0.96 (99% CI: 0.88, 1.04, P=0.18). Two separate sensitivity analyses produced results similar to that of the primary analysis for all three complication outcomes.
We found no evidence that the diagnosis of fibromyalgia increased the risk of in-hospital complications. Fibromyalgia seems to be associated with a reduction in in-hospital mortality, but this requires confirmation with a large prospective controlled study.