Table 1 Characteristics of initiators of celecoxib or NSAIDs (ibuprofen or diclofenac) in a cohort 18–65 years old between 1 July 2003 and 30 September 2004 in the MarketScan database: age at the date of the first medication use and co-morbidities/use of medications as defined during six months prior to the first medication use

From: Effects of aggregation of drug and diagnostic codes on the performance of the high-dimensional propensity score algorithm: an empirical example