Background High body mass index (BMI) has been inconsistently associated with prostate cancer (PCa) risk. Recent studies suggest that BMI trajectory modeling provides a more robust substitute method to predict cancer risk compared to static measures of BMI. However, only four studies have investigated lifetime BMI and PCa risk. We analyzed the effects of life course BMI trajectories on PCa risk based on data from the Epidemiological study of Prostate Cancer (EPICAP).

Methods EPICAP is a French population-based case-control study that enrolled 819 incident cases of PCa diagnosed in 2012 and 2013, aged less than 75 years old and residing in the département of Hérault, France. Controls were 879 age-matched men living in the same geographic area. Face to face interviews, using a standardized computerized questionnaire, gathered information about socio-demographic characteristics, medical history, lifestyle factors, physical activity, residential and occupational history. Anthropometric indicators have been collected through the questionnaire (self-report of height at 18 years old and weight every decades) or anthropometric measures at time of interview (height, weight, waist and hip circumferences). BMI trajectories were determined using group-based trajectory modeling to identify groups of men with similar patterns of BMI change through adulthood. Logistic regression models were used to assess odds ratios (ORs) for the associations between BMI trajectories and PCa risk. Analyses were systematically adjusted for age, family history of PCa and ethnicity. Stratified analyses were conducted by PCa aggressiveness according to the Gleason score. Seeking for relevant interaction between smoking status and BMI trajectories and given that smoking is a major risk factor for many types of cancer, known to decrease obesity, we performed stratified analyses according to smoking status.

Results We identified four BMI trajectories groups: ‘stable normal BMI’ (29.7%), ‘normal BMI to overweight’ (50.7%), ‘normal BMI to obesity’ (17.4%) and ‘overweight to obesity’ (2.2%). Men who had a BMI in the normal range at age 20 and developed overweight through adulthood had an increased risk of overall (OR 1.27, [0.99–1.62]) and aggressive (OR 1.57, [1.03–2.39]) PCa risk compared to men who maintained a normal BMI. Increased risk of aggressive PCa was also observed among never smokers who developed overweight (OR 3.32, [1.29–8.53]) or obesity (OR 4.19, [1.30–13.51]), but interaction was not significant.

Conclusion Our results suggest that BMI trajectories resulting in overweight or obesity during adulthood are associated with an increased risk of PCa, emphasizing the importance of maintaining a normal BMI throughout adulthood for cancer prevention.