Objective: This study assessed the association between respiratory symptoms and mortality in four cohorts of the general population in Norway aged 15-75 years and in selected subgroups in the pooled sample.
Methods: The study comprised 158,702 persons, who were drawn randomly from the Norwegian population register. All subjects received a standardized, self-administered questionnaire on 11 respiratory symptoms between 1972 and 1998, with follow-up of death until December 31, 2017. Analyses were performed on 114,380 respondents.
Results: The hazard of death was closely associated with sex, age, and education. The hazard ratios (HR) for death and the 95% confidence intervals (CI) by risk factors were similar in the four cohorts. After adjustment for demographic and environmental, modifiable factors, the HR for death was 1.90 (95% CI 1.80-2.00) for breathlessness score 3, 1.28 (1.21-1.37) for cough/phlegm score 5 and 1.09 (1.05-1.14) for attack of breathlessness/wheeze score 2 compared to the referent (no symptom), respectively. The cough/phlegm score was associated with death in current smokers but not in never smokers or ex-smokers. Breathlessness score was associated with death in men and women.
Conclusion: Among persons aged 45-75 years, respiratory symptoms were significant predictors of all cause mortality. Education and smoking habits influenced only the associations between coughing and mortality. The associations were independent of study sites.
Keywords: Cohort study; Men and women; Mortality; Respiratory symptoms.
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