The rate of moderate-to-severe chronic obstructive pulmonary disease exacerbations was @ % lower in the roflumilast group than in the placebo group according to a Poisson regression analysis ( roflumilast @ vs placebo @ ; rate ratio -LSB- RR -RSB- @ -LSB- @ % CI @-@ -RSB- , p = @ ) , and @ % lower according to a predefined sensitivity analysis using negative binomial regression ( @ vs @ ; @ -LSB- @-@ -RSB- , p = @ ) .