Impact of respiratory symptoms and oxygen saturation on the risk of incident venous thromboembolism—the Tromsø study

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with risk of venous thromboembolism (VTE). It remains unknown whether individual respiratory symptoms and lowered oxygen saturation (SpO(2)), individually and in combination with COPD, affect the risk of VTE. OBJECTIVES: To investigate whether measures of respiratory impairments including respiratory symptoms and SpO(2), individually and combined with COPD, were associated with an increased risk of VTE. METHODS: Spirometry, SpO(2), and self‐reported respiratory symptoms were collected in 8686 participants from the fifth (2001‐2002) and sixth (2007‐2008) surveys of the Tromsø Study. Incident VTE events were registered from the date of inclusion to December 31, 2016. Cox regression models with exposures and confounders as time‐varying covariates (for repeated measurements) were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for VTE. RESULTS: During a median follow‐up of 9.1 years, 330 participants developed incident VTE. Subjects with SpO(2) ≤ 96% (lowest 20th percentile) had a 1.5‐fold higher risk of VTE (adjusted HR, 1.48; 95% CI, 1.13‐1.93) compared with those with SpO(2) ≥ 98%. Severe respiratory symptoms (dyspnea, cough, and phlegm) were associated with a 1.4‐ to 2.0‐fold higher risk of VTE compared with no such symptoms. COPD, combined with respiratory symptoms or lowered SpO(2), had an additive effect on the VTE risk. CONCLUSIONS: Lowered SpO(2) and severe respiratory symptoms were associated with increased VTE risk. COPD combined with respiratory impairments had an additive effect on VTE risk, and may suggest particular attention on VTE preventive strategies in COPD patients with respiratory impairments.