Mortality ( n = 462 ) was compared by treatment allocation during 56 months ( interquartile range : 48 to 68 months ) of follow-up for subjects able ( n = 682 ) and unable ( n = 530 ) to walk 300 m in 6 min and with less ( Physical Ability Score [ PAS ] > 55 , n = 749 ) and more ( PAS 55 , n = 433 ) limitation by dyspnea or fatigue .