Interaction of factors related to the metabolic syndrome and vitamin D on risk of prostate cancer.
BACKGROUND
Factors related to the metabolic syndrome and low levels of vitamin D have been implicated as risk factors for prostate cancer. Insofar, no studies have assessed their joint effects on prostate cancer risk.


METHODS
We studied (a) the associations of vitamin D with the metabolic syndrome factors body mass index, systolic and diastolic blood pressure, and high-density lipoprotein cholesterol (HDL-C) and (b) the prostate cancer risk associated with these factors and especially their joint effects with vitamin D on risk of prostate cancer. We did a longitudinal nested case-control study on 132 prostate cancer cases and 456 matched controls from a cohort of 18,939 Finnish middle-aged men from the Helsinki Heart Study. The odds ratios (OR) of prostate cancer were assessed via conditional logistic regression analysis.


RESULTS
Apart from HDL-C, there was no linear association between the metabolic syndrome factors and vitamin D levels. In univariate analysis, men in the highest quartiles of body mass index (>28 kg/m(2)) and systolic blood pressure (>150 mmHg) showed a modest increase in risks of prostate cancer, with ORs of 1.37 (P = 0.16) and 1.53 (P = 0.05) when compared with the three lower quartiles, but low HDL-C entailed no prostate cancer risk. However, with all three factors present, the OR was 3.36 (P = 0.02), and jointly with low vitamin D (<or=40 nmol/L), the OR was 8.03 (P = 0.005) compared with those with no metabolic syndrome factors and intermediate levels of vitamin D. There was an interaction between vitamin D and the metabolic syndrome factors so that a clustering of these factors entailed high risk of prostate cancer but only if vitamin D level was low (<or=40 nmol/L). If it was at intermediate levels, the metabolic syndrome factors entailed no prostate cancer risk.


CONCLUSIONS
We conclude that the prostate cancer risk associated with factors related to the metabolic syndrome is strongly conditioned by levels of vitamin D.
Tuohimaa
Pentti
P
Medical School, University of Tampere, Department of Clinical Chemistry, Tampere University Hospital, Finland. Pentti.Tuohimaa@uta.fi
Tenkanen
Leena
L
Syvälä
Heimo
H
Lumme
Sonja
S
Hakulinen
Timo
T
Dillner
Joakim
J
Hakama
Matti
M
D000704:Analysis of Variance; D016022:Case-Control Studies; D005387:Finland / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications*; D008875:Middle Aged; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012307:Risk Factors; D014807:Vitamin D / Q000097:blood*
D014807:Vitamin D