Adult lifetime body mass index trajectories and endometrial cancer risk

Objective To identify body mass index (BMI) trajectories in adult life and to examine their association with endometrial cancer (EC) risk, also exploring whether relations differ by hormonal replacement therapy use. Design Pooled analysis of two case-control studies. Setting Italy and Switzerland. Population A total of 458 EC cases and 782 controls. Methods We performed a latent class growth model to identify homogeneous BMI trajectories over six decades of age, with a polynomial function of age. Odds ratios (ORs) and the corresponding 95% CI for EC risk were derived through a multiple logistic regression model, correcting for classification error. Main outcome measures The relation of BMI trajectories with endometrial cancer. Results We identified five BMI trajectories. Compared with women in the 'Normal weight-stable' trajectory, a reduction by about 50% in the risk of EC emerged for those in the 'Underweight increasing to normal weight' (95% CI 0.28-0.99). The 'Normal weight increasing to overweight' and the 'Overweight-stable' trajectories were associated with, respectively, an excess of 3% (95% CI 0.66-1.60) and of 71% (95% CI 1.12-2.59) in cancer risk. The OR associated to the trajectory 'Overweight increasing to obese' was 2.03 (95% CI 1.31-3.13). Stronger effects emerged among hormonal replacement therapy never users (OR 2.19 for the 'Overweight-stable' trajectory and OR 2.49 for the 'Overweight increasing to obese' trajectory). Conclusions Our study suggests that longer exposure to overweight and obesity across a lifetime is associated with an increased risk of endometrial cancer. Weight during adulthood also appears to play an important role.