Shiftwork and Prostate-Specific Antigen in the National Health and Nutrition Examination Survey

Background Shiftwork has been implicated as a risk factor for prostate cancer. Results from prior studies have been mixed but generally support an association between circadian disruption and prostate cancer. Our aim was to investigate the relationship between shiftwork and prostate-specific antigen (PSA) test obtained as part of the National Health and Nutrition Examination Survey (NHANES) study. Methods We combined three NHANES surveys (2005-2010) to obtain current work schedule among employed men aged 40 to 65 years with no prior history of cancer (except nonmelanoma skin cancer). Men who reported working regular night shifts or rotating shifts were considered shiftworkers. We obtained the total and percentage free PSA test results for these men and dichotomized total PSA into less than 4.0 ng/mL or 4.0 ng/mL or greater and total PSA of 4.0 ng/mL or greater combined with percentage free PSA less than or equal to 25%. Using multivariable logistic regression models, we compared PSA level among current shiftworkers and nonshiftworkers. All statistical tests were two-sided. Results We found a statistically significant, age-adjusted association between current shiftwork and elevated PSA at the 4.0 ng/mL or greater level (odds ratio = 2.48, 95% confidence interval [CI] = 1.08 to 5.70; P = .03). The confounder-adjusted odds ratio was 2.62 (95% CI = 1.16 to 5.95; P = .02). The confounder-adjusted odds ratio for those with total PSA of 4.0 ng/mL or greater and free PSA less than or equal to 25% was 3.13 (95% CI = 1.38 to 7.09; P = .01). Conclusions We observed a strong positive association with shiftwork and elevated PSA level. Our data support the notion that sleep or circadian disruption is associated with elevated PSA, indicating that shiftworking men likely have an increased risk of developing prostate cancer.