Objective: To investigate the relationship between body mass index (BMI) and prostate specific antigen (PSA) levels in Jamaican men.
Methods: Men, 40-79 years old, attending public and private urology clinics in Kingston, Jamaica were recruited to a case-control study on the role of dietary and lifestyle factors on prostate cancer. Trained interviewers administered questionnaires and measured weight and height using standardized techniques. Blood samples for PSA were measured at a central laboratory using a micro-particle enzyme immunoassay method. Prostate biopsy was used to confirm prostate cancer. Multivariable linear regression was used to examine the relationship between BMI and PSA separately in the cases and controls.
Results: Data from 501 men (233 cases and 263 controls) were assessed. Thirty-five per cent of subjects were overweight and 13% were obese. Among cases, the median PSA was 35.3 ng/dL in normal weight, 26.1 ng/dL in overweight and 14.5 ng/dL in obese men (p = 0.02). For controls, median PSA was 2.0 ng/dL in normal weight, 1.3 ng/dL in overweight and 1.1ng/dl in obese men (p = 0.01). Among cases, BMI was negatively associated with PSA (B(SE) per 5 kg/m2 (BMI difference = -0.51 (0.13); p < 0.01) and remained significant after adjustment for age, sexual activity, smoking, use of statins and tumour grade. For controls, the BMI was also inversely related to the PSA (B(SE) per 5 kg/m2 difference -0.17 (0.07)) but the effect became of borderline significance after adjusting for age.
Conclusions: Prostate specific antigen was inversely related to body mass index in Jamaican men with prostate cancer. Clinicians should consider this association when interpreting PSA results.