The index fill was the first fill date for a qualifying medication in one of the three study cohorts in calendar year 2010. Individuals could be included in multiple disease-state-centric cohorts and the index date was allowed to vary between cohorts for such individuals. For each of the three cohorts, a series of five washout periods of increasing length – 3, 6, 12, 24 and 36 months – was used to assess prevalent use and create increasingly restrictive incident user cohorts (Figure 1). A treatment-naive definition of incident use was used, in which having at least one prescription claim for any cohort-specific study medication in the washout period, regardless of whether or not it matched the index drug or index drug class, constituted prevalent use. For example, an antihyperlipidemic user whose index medication was simvastatin would be considered a prevalent user if, in the given washout period, they had a claim for simvastatin, another statin or any other antihyperlipidemic agent. This is the strictest definition of prevalent use and is commonly employed in comparative effectiveness studies of pharmacotherapies, in which subjects are required to have never been treated for the condition under study to ensure similar baseline risks of the study outcome across groups. Inclusion in each of the incident user cohorts also required continuous insurance enrollment for the duration of the given washout period, defined by having a gap in coverage no greater than 7 days. This is necessary in incident user designs to ensure complete assessment of a subject's medication use for the entire washout period. A sensitivity analysis allowing a 30-day gap in insurance coverage was conducted; the results were unchanged, so the findings are presented using a 7-day coverage gap.