Statin and statin-fibrate use was significantly associated with increased myositis risk in a managed care population.
OBJECTIVE
We quantified the risk of myositis associated with statin and fibrate drug use with other covariates within a managed care organization (MCO) population.


METHODS
The study spanned the years 1999-2003. Myositis cases had creatine kinase (CK) >or=10x upper limit of normal and a myopathy diagnosis. Exposures of statins, fibrates, and other drugs were assessed with age, gender, and indicators of suspected myopathy risk. Exposures were first analyzed within a cohort with CK monitoring and then within a more general secondary cohort. Adjusted relative risks (RRs) and incidence rates of myositis were generated by Poisson regression.


RESULTS
Myositis was significantly associated with statin monotherapy (RR 2.8 [95% confidence interval, CI=1.3-5.9]), statin-fibrate combination therapy (9.1 [95% CI=3.5-23]), comorbid liver disease (4.3 [95% CI=1.5-13], and/or renal disease (2.5 [95% CI=1.3-5.0]). Myositis rates per covariate pattern ranged from 33 to 6,400 per 100,000 person-years. The mean time to event was 1.7 years for statin-fibrate use, 2.0 years for statins alone, and 2.1 years for unexposed. Within the secondary cohort, RRs increased up to 10 times further away from the null.


CONCLUSIONS
Statins, with or without fibrates, and liver and renal disease were significantly associated with increased myositis risk in an MCO population.
McClure
David L
DL
Clinical Research Unit, Kaiser Permanente Colorado, Denver, CO 80237-8066, USA. david.1.mcclure@kp.org
Valuck
Robert J
RJ
Glanz
Morton
M
Murphy
James R
JR
Hokanson
John E
JE
D000367:Age Factors; D000368:Aged; D002995:Clofibric Acid / Q000009:adverse effects* / Q000627:therapeutic use; D015331:Cohort Studies; D016001:Confidence Intervals; D015986:Confounding Factors, Epidemiologic; D003402:Creatine Kinase / Q000097:blood; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D006949:Hyperlipidemias / Q000097:blood / Q000150:complications / Q000188:drug therapy; D000960:Hypolipidemic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D007674:Kidney Diseases / Q000150:complications; D008107:Liver Diseases / Q000150:complications; D008297:Male; D008329:Managed Care Programs; D008875:Middle Aged; D009220:Myositis / Q000097:blood / Q000139:chemically induced* / Q000150:complications; D016017:Odds Ratio; D016016:Proportional Hazards Models; D012306:Risk; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors
D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D000960:Hypolipidemic Agents; D002995:Clofibric Acid; D003402:Creatine Kinase