[en] OBJECTIVES: To capture changes in the quality of life (QoL) occurring in patients with osteoarthritis (OA) during treatment with non-specific non-steroidal anti-inflammatory drugs (NSAIDs) and to identify factors that predict such changes. METHODS: A naturalistic, prospective follow up of 783 patients with OA in whom primary care physicians decided to start treatment with non-selective NSAIDs. Short Form-36 (SF-36) and the Western Ontario and McMaster Universities OA index (WOMAC) were assessed at baseline and after 3 months. Baseline results were compared with QoL values in 4800 subjects randomly selected from the general population. Multiple regression analysis was performed to identify determinants of QoL at baseline and measures influencing changes in SF-36 or WOMAC during follow up. RESULTS: All QoL dimensions were significantly (p<0.01) decreased in patients with OA compared with controls. Significant improvement (p<0.05) in four dimensions of the SF-36 (vitality, role emotional, role physical, bodily pain) and in all components of the WOMAC was seen between baseline and month 3. Older age, female sex, longer duration of OA, and a higher number of comorbidities were the major determinants of a poor QoL at baseline. Maximal benefit from non-specific NSAIDs was seen in patients with the most severe impairment in QoL and the shortest duration of OA. CONCLUSION: OA negatively impacts all dimensions of the QoL. Non-specific NSAIDs improve the QoL in patients with OA treated in a "real life setting". The profile of patients receiving maximal benefit from such treatment may be of interest for health providers, enabling them to decide who should preferentially be given cytoprotective treatments or coxibs.