GOLD classifications and mortality in chronic obstructive pulmonary disease: the HUNT Study, Norway.

BACKGROUND How different Global Initiative for Chronic Obstructive Lung Disease (GOLD) classifications of chronic obstructive pulmonary disease (COPD) predict mortality is unclear. OBJECTIVE To examine the association of spirometric GOLD grades and the new ABCD groups with mortality, and to compare their informativeness in relation to mortality. METHODS We studied 1540 people with post-bronchodilator COPD who participated in the Norwegian Nord-Trøndelag Health Study 1995-1997 and were followed up on all-cause mortality until May 2012. The associations of spirometric GOLD grades and ABCD groups with mortality were estimated by sex specific adjusted HRs from Cox regression and standardised mortality ratios. To assess the informativeness of spirometric GOLD grades and ABCD groups at predicting mortality we used the difference in twice the log-likelihood of a Cox regression model with and without each COPD classification. RESULTS The distribution of participants was 28% in GOLD 1, 57% in GOLD 2, 13% in GOLD 3 and 2% in GOLD 4, in contrast to 61% in group A, 18% in group B, 12% in group C and 10% in group D. During a median of 14.6 years of follow-up, 837 people (54%) died. Mortality increased gradually from GOLD 1 to 4, while it was generally similar in groups A and B, and in groups C and D. Spirometric GOLD grades were substantially more informative than ABCD groups at predicting mortality. CONCLUSIONS Spirometric GOLD grades predicted mortality better than the new ABCD groups among people with COPD from a Norwegian general population.