Lung function, respiratory symptoms and incident venous thromboembolism during a 44-year follow-up

Background: Chronic obstructive pulmonary disease (COPD) and infections are risk factors for venous thromboembolism (VTE), but the reasons behind the associations are not fully known. Few studies have investigated whether lung function and respiratory symptoms in individuals without COPD are associated with VTE. Objectives: To study the incidence of VTE in individuals without COPD and other major VTE risk factors, in relation to baseline lung function and respiratory symptoms, through a 44-year follow-up prospective cohort study. Methods: As part of a health screening program, a total of 20,253 men and 7361 women underwent a baseline examination from 1974 to 1992, including a spirometry test and a self-administered questionnaire about respiratory symptoms, e.g., chronic bronchitis, cough, phlegm, and dyspnoea. Lung function was assessed through quartiles of forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC). Through linkage with national registers, all individuals were followed for incidence of VTE. Results: Respiratory symptoms (cough and dyspnoea) at baseline were associated with an increased risk of incident VTE in women after adjustments for age, height, BMI, smoking status, varicose veins, and FEV1/FVC. The adjusted hazard ratio in relation to chronic bronchitis was 1.57 (95% confidence interval 1.17–2.11). Poor lung function was not associated with an increased risk of VTE after adjustments for potential confounders. Conclusion: Women with respiratory symptoms of cough and dyspnoea without COPD have an increased risk of VTE, independent of lung function and major VTE risk factors. Further studies are needed to confirm the association and to study the clinical applicability of the results.