Variations in Incidence of Venous Thromboembolism in Low-, Middle- and High-Income Countries.

To examine the rates of VTE in high-income, upper middle-income and lower middle/low-income countries (World Bank Classification).
We examined the rates of VTE in high-income, upper middle-income and lower middle/low-income countries (World Bank Classification) in a cohort derived from four prospective international studies (PURE, HOPE-3, ORIGIN, COMPASS). The primary outcome was a composite of pulmonary embolism, deep vein thrombosis and thrombophlebitis. We calculated age- and sex- standardized incidence rates (per 1000 person-years) and used a Cox frailty model adjusted for covariates to examine associations between the incidence of VTE and country income level. A total of 215,307 individuals (1·5 million person-years of follow-up) from high-income (n = 60,403), upper middle-income (n = 42,066) and lower middle/low-income (n = 112,838) countries were included. The age- and sex-standardized incidence rates of VTE per 1000 person-years in high-, upper middle- and lower middle/low-income countries were 0·87, 0·25 and 0·06, respectively. After adjusting for age, body mass index, smoking, antiplatelet therapy, anticoagulant therapy, education level, ethnicity, and incident cancer diagnosis or hospitalization, individuals from high-income and upper middle-income countries had a significantly higher risk of VTE than those from lower middle/low-income countries (hazard ratio [HR] 3·57, 95% confidence interval [CI] 2·40-5·30 and HR 2·27, 95%CI 1·59-3·23, respectively). The effect of country income level on VTE risk was markedly stronger in people with a lower BMI, hypertension, diabetes, non-white ethnicity and higher education.
The rates of VTE are substantially higher in high-income than low-income countries. The factors underlying the increased VTE risk in higher income countries remain unknown.
We investigated the burden of VTE by country income by combining information from 4 large prospective studies (215,307 individuals from 53 countries). This is the largest study on the global incidence of VTE published to date. We observed a higher incidence of VTE in richer compared to poorer countries. We also demonstrated that differences in rates of VTE are not explained by risk factors commonly associated with VTE. Further study is needed to understand whether these findings can be explained by differences in genetic or other markers, or whether they are due to differences in access to health care.

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