Obesity in adolescent men increases the risk of venous thromboembolism in adult life.

Background As the population of obese and severely obese young adults grows, it is becoming increasingly important to recognize the long-term risks associated with adolescent obesity. Objectives This study aimed to determine the association between body mass index (BMI) in young men at enlistment for military service and later risk of venous thromboembolism (VTE). Methods Nationwide register-based prospective cohort study of men enlisting 1969 to 2005, followed through the Swedish National Patient and Cause of Death registries. We identified 1 639 838 men (mean age, 18.3 years) free of prior venous thromboembolism, of whom 29 342 were obese (BMI 30 to <35 kg m(-2)) and 7236 severely obese (BMI >= 35 kg m(-2)). The participants were followed until a first registered diagnosis of VTE. Results During a median follow-up of 28 years (interquartile interval, 20 to 36 years), 11 395 cases of deep vein thrombosis and 7270 cases of pulmonary embolism were recorded. Compared with men with a BMI of 18.5 to <20 kg m(-2), men with higher BMI in young adulthood showed an incrementally increasing risk of VTE that was moderately but significantly increased already at normal BMI levels. Adolescent obese men with a BMI of 30 to 35 kg m(-2) had an adjusted hazard ratio of 2.93 (95% confidence interval, 2.65 to 3.24) for VTE. Severely obese men with a BMI of >= 35 kg m(-2) had a hazard ratio of 4.95 (95% confidence interval, 4.16 to 5.90). Conclusions Men who were obese or severely obese in young adulthood had a marked increase in risk of VTE.