Patients at greater risk of first pneumonia had more severe obstruction ( forced expiratory volume in one second/forced vital capacity < @ % ) and either a body mass index < @ kg/m ( @ ) ( hazard ratio @ , @ % confidence interval @-@ @ ; n = @ ) or a pneumonia history and greater comorbidities ( hazard ratio @ , @ % confidence interval @-@ @ ; n = @ ) relative to the cluster with the lowest pneumonia risk ( reference ; n = @ ) .