Patients at greater risk of first pneumonia had more severe obstruction ( forced expiratory volume in one second/forced vital capacity < 46 % ) and either a body mass index < 19 kg/m ( 2 ) ( hazard ratio 7.8 , 95 % confidence interval 4.7-13 .0 ; n = 144 ) or a pneumonia history and greater comorbidities ( hazard ratio 4.8 , 95 % confidence interval 3.0-7 .7 ; n = 374 ) relative to the cluster with the lowest pneumonia risk ( reference ; n = 1310 ) .