Daily physical activity affects exercise capacity in patients with idiopathic pulmonary fibrosis

[Purpose] The aim of this study was to determine which factors, including pulmonary, physical, and mental functions; dyspnea; and daily physical activity (PA) affect the 6-minute walk distance (6MWD) in IPF patients. [Subjects and Methods] The pulmonary, physical, and mental functions; dyspnea; PA; and 6MWD were assessed in 38 outpatients with IPF. PA was represented by the mean number of steps per day. [Results] The mean 6MWD was 443.8 m (SD, 98.5), and the mean number of steps per day showing PA was 5148.4 (SD, 3295.7). The 6MWD was correlated with age, base dyspnea index, vital capacity (VC), diffusion capacity of carbon monoxide, quadriceps force (QF), dyspnea during the 6-minute walk test, and PA. Stepwise multiple regression analysis revealed that VC (β=0.382), QF (β=0.272), and PA (β=0.574) were contributing factors of the 6MWD. [Conclusion] In patients with IPF, PA has a greater effect on the 6MWD than VC and QF. The evaluation of daily PA, in addition to physiological and muscle functions, is important in patients with IPF.