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Smoking, but not most other modifiable traditional CVD risk factors, linked to increased VTE risk
A meta-analysis of nine prospective studies showed that the modifiable traditional risk factors for CVD — hypertension, hyperlipidemia and diabetes — were not associated with an increased risk for venous thromboembolism.
However, researchers found an association between cigarette smoking and provoked VTE.
Bakhtawar K. Mahmoodi, MD, PhD, MPH, of the department of cardiology and internal medicine at St. Antonius Hospital in Nieuwegein, the Netherlands, and colleagues conducted an individual level random-effect meta-analysis. All studies included measured baseline CVD risk factors and validated VTE events.
After harmonizing definitions across all studies, the researchers compiled estimates regarding overall VTE, provoked VTE, unprovoked VTE, pulmonary embolism and deep vein thrombosis. Provoked VTE was defined as occurring in the presence of one or more established risk factors for VTE.
The overall mean follow-up for the 244,865 participants was 4.7 to 19.7 years per study. After adjustment for age, sex and BMI, the following HRs were found for overall VTE: for hypertension, 0.98 (95% CI, 0.89-1.07); for hyperlipidemia, 0.97 (95% CI, 0.88-1.08); for diabetes, 1.01 (95% CI, 0.89-1.15); for current smoking, 1.19 (95% CI, 1.08-1.32).
An inverse association (when modeled continuously) was found for systolic BP (HR = 0.79; 95% CI, 0.68-0.92 at systolic BP of 160 mm Hg vs. 110 mm Hg). No association was found for diastolic BP or lipid measures for an increased VTE risk.
“Our findings suggest that previously reported positive associations between traditional CVD risk factors and VTE are likely caused by not accounting for confounding factors,” Mahmoodi and colleagues wrote.
In a VTE subtype analyses, cigarette smoking was linked to an increased risk for provoked VTE (fully adjusted HR = 1.36; 95% CI, 1.22-1.52). No association was found between cigarette smoking and unprovoked VTE (fully adjusted HR = 1.08; 95% CI, 0.9-1.29).
“The study published by Mahmoodi et al … represents an advance over prior studies because it is an individual-level meta-analysis … and is well powered (n = 4,910 VTE events), with harmonized risk factor definitions across studies, and careful measurement of the outcomes of interest,” Sonia S. Anand, MD, PhD, FRCPC, from the department of medicine and epidemiology at McMaster University in Hamilton, Ontario, Canada, wrote in a related editorial.
“We learn a great deal from the meta-analysis by Mahmoodi and colleagues, for example, that smokers have a higher risk of VTE, whereas there are no strong signals for hypertension, diabetes … and elevated cholesterol. Although the effect size is low, it is likely that many cases of VTE are caused by the presence of multiple risk factors, all with small effects (ie, risk ratios < 2.0) that increase risk above a certain threshold and clinical thrombosis develops,” Anand wrote. – by Suzanne Reist
Disclosure: The researchers and Anand report no relevant financial disclosures.