Selection effects on an estimation of long-term changes in pulmonary function

To reveal the association of initial pulmonary function level with subseque nt mortality and participation in a follow-up reexamination, a prospective cohort study was performed. Female residents in a volcanic area of southern Kyushu, Japan, were followed up for their vital status and the pulmonary f unction 15 years after they received the first pulmonary function test. A c ohort of 512 Japanese female residents who were examined for pulmonary func tion as indicated by forced expiratory volume and forced expiratory volume in one second was measured in a baseline examination in 1980. After 15 year s, 35 females were lost to follow-up. Of the remaining 477 females, 340 and 137 females provided good and poor levels of pulmonary function tests (PFT ) at baseline, respectively. Mortality by 1995 in the poor PFT group was si gnificantly higher than that in the good PFT group (33.6% vs 9.4%). The mor tality differences were still highly significant when the 35 lost cases wer e included as all alive. Among the 399 survivors, the nonparticipation rate in the reexamination in 1995 was significantly higher in the poor PFT grou p than that in the good PFT group (80.2% vs 69.5%). The results of the pres ent study, a longitudinal study of pulmonary function, provide evidence of selection effects due to death or failure to participate in a subsequent re examination. (C) 1999 Academic Press.