Adverse events were reported by 648 ( 67 % ) of 968 patients receiving roflumilast and by 572 ( 59 % ) of 967 patients in the placebo group ; adverse event-associated patient withdrawal from the study was also more common in the roflumilast group ( 104/968 [ 11 % ] ) than in the placebo group ( 52/967 [ 5 % ] ) .