Body mass index and mortality in men with prostate cancer.
BACKGROUND
Body Mass index (BMI) has been shown to affect risk and mortality of several cancers. Prostate cancer and obesity are major public health concerns for middle-aged and older men. Previous studies of pre-diagnostic BMI have found an increased risk of prostate cancer mortality in obese patients.


OBJECTIVE
To study the associations between BMI at time of prostate cancer diagnosis and prostate cancer specific and overall mortality.


METHODS
BMI was analyzed both as a continuous variable and categorized into four groups based on the observed distribution in the cohort (BMI < 22.5, 22.5 < 25, 25 < 27.5 and ≥27.5 kg/m2). The association between BMI and mortality was assessed using stratified Cox proportional hazards models and by fitting regression splines for dose response analysis in 3,161 men diagnosed with prostate cancer. After 11 years of follow up via linkage to the population-based cause of death registry, we identified 1,161 (37%) deaths off which 690 (59%) were due to prostate cancer.


RESULTS
High BMI (BMI ≥ 27.5 kg/m2) was associated with a statistically significant increased risk of prostate cancer specific mortality (HR:1.44, 95% CI: 1.09-1.90) and overall mortality (HR:1.33, 95% CI: 1.09-1.63) compared to the reference group (BMI 22.5 < 25 kg/m2). Additionally, men with a low BMI (<22.5 kg/m2 ), had a statistically significant increased risk of prostate cancer specific mortality (HR:1.33, 95% CI: 1.02-1.74) and overall mortality (HR:1.36, 95% CI: 1.11-1.67) compared to the reference. However, this effect disappeared when men who died within the first two years of follow-up were excluded from the analyses while the increased risk of prostate cancer specific mortality and overall mortality remained statistically significant for men with a BMI ≥ 27.5 kg/m2 (HR:1.44, 95% CI: 1.09-1.90 and HR: 1.33, 95% CI: 1.09-1.63, respectively).


CONCLUSIONS
This study showed that a high BMI at time of prostate cancer diagnosis was associated with increased overall mortality.
Department of Statistics and Quantitative Methods, University of Milano-Bicocca,, Milan, Italy.|Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Anna
A
Cantarutti
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Stephanie E
SE
Bonn
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Hans-Olov
HO
Adami
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Henrik
H
Grönberg
Department of Statistics and Quantitative Methods, University of Milano-Bicocca,, Milan, Italy.|Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Rino
R
Bellocco
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Katarina
K
Bälter
D000368:Aged; D015992:Body Mass Index; D016022:Case-Control Studies; D015897:Comorbidity; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology; D016016:Proportional Hazards Models; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000401:mortality; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
body mass index; epidemiology; mortality; prostate cancer