In general, men who smoke have lower prostate specific antigen (PSA) levels compared to non-smokers, CDC researchers say.
"Men who have never smoked were less likely to have an abnormal result on PSA screening and a diagnostic biopsy, possibly resulting in fewer screen-detected prostate cancers, compared with men who have never smoked," Dr Jun Li from the Centres for Disease Control and Prevention, Atlanta, Georgia told Reuters Health in an email.
"Studies have consistently shown that current smokers have an increased risk of fatal prostate cancer," Dr Li said. "Delayed detection of prostate cancer due to the inverse relationship between smoking and PSA may contribute in part to worse health outcomes of prostate cancer among smokers."
The new finding is drawn from PSA data collected by the National Health and Nutrition Examination Survey (NHANES) 2001-2006 from 3,820 men age 40 or older.
PSA increase with age
Total and free PSA increased with age and decreased with increasing body mass index (BMI), the research team reported online February 14 in The Journal of Urology.
Median total PSA values were lower for current smokers (0.8 ng/mL) than for former smokers (0.95 ng/mL) or never smokers (0.90 ng/mL).
Median free PSA values were also lower for current smokers (0.24 ng/mL) than for former smokers (0.28 ng/mL) or never smokers (0.27 ng/mL).
In multivariate linear regression models, the predicted geometric mean of total PSA was 7.9% lower among current smokers and 12.2% lower among former smokers than among never smokers.
Diabetes associated with PSA decrease
Each five-year age increase was associated with a 13.7% increase in mean total PSA, whereas each five-point increase in BMI was associated with a 6.9% decrease in mean total PSA. Diabetes was associated with a 14.8% decrease in mean total PSA.
Mean total PSA was 16.5% higher in men with benign prostatic hypertrophy than in men without BPH, and mean total PSA was 14.1% higher among non Hispanic black versus non Hispanic white men.
As for mean percent free PSA, results were lower for former smokers than for current smokers, higher with diabetes, lower with increasing age, and lower among Mexican-Americans than among non Hispanic whites.
Incorporate conditions to assess cancer risk
"Besides smoking, we also confirmed inverse associations between diabetes and obesity with PSA," Dr Li said. "Although the magnitude of these inverse associations with PSA level alone may not be substantial, the joint effect of smoking, obesity, and diabetes associated with PSA may have greater clinical implications given the high prevalence of these conditions. In clinical practice, physicians should be aware that these health conditions may mask patients' true risk for prostate cancer."
"Often-used PSA cut-point (values need) to be modified in terms of a patient's smoking, obesity, and diabetes status," Dr Li concluded. "Furthermore, all these health conditions should be incorporated into an individualised risk calculator to better assess prostate cancer risk."
(David Douglas, Reuters Health, March 2012)
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