Prevalence and trend of COPD from 1995-1997 to 2006-2008: The HUNT study, Norway

Background: COPD is a major cause of morbidity and mortality across the world and new estimates of prevalence and trend are of great importance. We aimed to estimate the prevalence and trend of COPD from 1995-1997 to 2006-2008 in Norwegian adults >= 40 years from the Nord-Trondelag Health Study. Material and methods: COPD was assessed using a fixed-ratio and lower limit of normal (LLN) criteria. Pre-bronchodilator spirometry was performed during 1995-1997 (n = 7158) and 2006-2008 (n = 8788). The prevalence of COPD was weighted using the inverse probability of selection and predicted probability of response. Results: The prevalence of pre-bronchodilator COPD was 16.7% in 1995-1997 and 14.8% in 2006-2008 using fixed-ratio criteria, and 10.4% in 1995-1997 and 7.3% in 2006-2008 using LLN criteria. The prevalence of LLN COPD was higher among men (13.0% in 1995-1997, 7.7% in 2006-2008) than women (8.0% in 1995-1997, 6.9% in 2006-2008). From 1995-1997 to 2006-2008, the prevalence decreased among men but remained relatively stable among women. Over the 11-year period, the cumulative incidence of pre-bronchodilator COPD using LLN criteria was 3.3% and 2.7% among men and women respectively. The prevalence of self-reported asthma and respiratory symptoms increased. Conclusions: The prevalence declined in men but not in women from 1995-1997 to 2006-2008, and was consistently higher among men than women.