Obesity and Haematology

Dr. HWANG Yu Yan - Council Member, HKOS

Venous thromboembolism is increasingly common in Chinese. It is potentially fatal and carries significant morbidity. Pulmonary hypertension and post thrombotic syndrome are some of the long term sequelae. Among all the risk factors, obesity is one of the avoidable and reversible predisposing conditions. Obesity has been shown to increase risk of venous thromboembolism (VTE) in a number of studies. Being overweight (BMI between 25 and 30kg/m^2) increased the risk of VTE by 1.7-fold (OR 1.7 95% C.I. 1.55-1.87) whereas obesity (BMI above 30kg/m^2) increased this risk by 2.4-fold (OR 2.4 95% C.I. 2.15-2.78). Risk of recurrent VTE is also increased in obese subjects. In a study of recurrent VTE, it was found that the probability of recurrence was 9.3%, 16.7% and 17.5% among normal, overweight and obese individuals respectively. Furthermore, obesity acts synergistically with other risk factors of thrombosis, further increasing the risk of VTE in at risk individuals. For example, the risk of VTE in obese women taking oral contraceptives is 24 fold higher than women with normal body mass index who did not take contraceptives. The exact mechanism by which obesity affects coagulation cascade is yet to be defined. It is likely a complex model and is partly related to factor VIII resistance to activated protein C in obese individuals. Therefore, weight management is of paramount importance in preventing thromboembolism.