Some of the most commonly used painkillers can increase long-term users' heart-attack risk by more than a third, an in-depth study into their side-effects has shown. The study, published in The Lancet medical journal last May 30, it was realized by researchers of the University of Oxford's Clinical Trial Service Unit and Epidemiological Unit in cooperation with the Institute of Pharmacology, Catholic University of Rome, and funded by Medical research council and by British heart foundation.