Objective: We investigated the relationship between respiratory symptoms and mortality from all causes in a large Norwegian population. We also examined mortality during separate periods of follow-up.
Design: Population-based, prospective cohort study.
Setting and subjects: A total of 19,998 men and women were randomly selected from the general population of Oslo. They received a postal respiratory questionnaire. The response rate was 88%.
Main outcome measures: The relationship between 11 respiratory symptoms and 30 years of total mortality was investigated separately for men and women by multivariate analyses with adjustment for age, smoking habits and occupational exposure to air pollution.
Results: The relative mortality risk in comparison with asymptomatic subjects varied from 1.36 (95% confidence interval 1.25-1.48) for cough symptoms to 2.46 (2.13-2.85) for severe dyspnoea amongst men; the corresponding rates amongst women were 1.28 (1.16-1.40) and 1.52 (1.31-1.75), respectively. The relative risk of mortality in individuals with 1-3, 4-6 and 7 or more symptoms was 1.20, 1.60 and 2.53 (P for trend 0.000) in men and 1.14, 1.47 and 1.84 (P for trend 0.000) in women. Except for cough, the mortality rates associated with respiratory symptoms decreased significantly during follow-up. The positive association between respiratory symptoms and mortality was observed in people with and without cardiopulmonary diseases.
Conclusions: Respiratory symptoms were significant predictors of mortality from all causes over 30 years, decreased during follow-up and were still increased after 30 years.