Date of Degree
PhD (Doctor of Philosophy)
Robert B. Wallace
Statins are cholesterol-lowering medications with immunologic properties. To assess the role of statins on incident immune-mediated conditions, a modified case-cohort study was performed using administrative databases from the Midwest Veterans Administration (VA) region. A comparison sub-cohort was formed by randomly sampling 10,000 subjects with medical and pharmacy benefits during fiscal year (FY) 2002. Cases were identified by inpatient or outpatient medical claims using International Classification of Disease, Ninth Revision (ICD-9) codes between FY 2003-2004. All subjects needed at least one year of medical claims and at least one pharmacy claim. The incident cases (n=28,642) included non-mutually exclusive groups of immune-mediated (n=2,327), infectious (n=8,221), and non-immunologic (n=10,730) diagnoses. Demographic and medical variables were obtained from FY 2001-2004, and pharmacologic data from FY 2002-2004. Cox proportional hazards regression modeling was used to estimate hazard ratios for the current statin use (within the last 180 days) and former statin use, compared to non-users, including time-dependant variables for demographic factors, comorbidity as measured by Elixhauser and Chronic Disease Score variables, medications, and visit rates after initiating statins. Current statin use was associated with decreased diagnoses rates of psoriasis; rheumatoid arthritis; inflammatory bowel diseases, including ulcerative colitis and Crohn disease; diffuse connective tissue diseases, including systemic lupus erythematosus; ankylosing spondylitis; bacterial pneumonia; urinary tract infection; cellulitis; sepsis; candidiasis; osteomyelitis; and tuberculosis. Former statin use was also associated with increased rates of polymyalgia rheumatica, sepsis, and osteomyelitis. Statin use was not associated with other spondylitis, multiple sclerosis, thyroiditis, sarcoidosis, temporal arteritis, influenza, shingles, histoplasmosis, or pyelonephritis. Although current statin use appeared protective for some study conditions, selection bias, misclassification, healthy user effects, adherence bias, confounding by indication, and surveillance bias were considered as possible explanations of the study findings.
Copyright 2008 Dominic J Cirillo