The value of the case—control approach for the evaluation of the risk of upper gastrointestinal bleeding associated with the previous use of non-steroidal anti-inflammatory drugs

Several studies have reported an association between upper gastrointestinal bleeding (UGIB) and the previous use of acetylsalicylic acid (ASA) [1–11] or non-steroidal anti-inflammatory drugs (NSAIDs) as a whole [12–14]. However, specific estimates for individual drugs are not available because the lower prevalence of use of each individual NSAID — compared with that of ASA — limits the statistical power of any analytical study designed to quantify individual risks.