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Is the inverse association between selenium and bladder cancer due to confounding by smoking?

Abstract

Selenium has been linked to a reduced risk of bladder cancer in some studies. Smoking, a well-established risk factor for bladder cancer, has been associated with lower selenium levels in the body. We investigated the selenium-bladder cancer association in subjects from Maine, New Hampshire, and Vermont in the New England Bladder Cancer Case-Control Study. At interview (2001-2005), participants provided information on a variety of factors, including a comprehensive smoking history, and submitted toenail samples, from which we measured selenium levels. We estimated odds ratios and 95% confidence intervals among 1,058 cases and 1,271 controls using logistic regression. After controlling for smoking, we saw no evidence of an association between selenium levels and bladder cancer (for fourth quartile vs. first quartile, odds ratio (OR) = 0.98, 95% confidence interval (CI): 0.77, 1.25). When results were restricted to regular smokers, there appeared to be an inverse association (OR = 0.76, 95% CI: 0.58, 0.99); however, when pack-years of smoking were considered, this association was attenuated (OR = 0.91, 95% CI: 0.68, 1.20), indicating potential confounding by smoking. Despite some reports of an inverse association between selenium and bladder cancer overall, our results, combined with an in-depth evaluation of other studies, suggested that confounding from smoking intensity or duration could explain this association. Our study highlights the need to carefully evaluate the confounding association of smoking in the selenium-bladder cancer association.

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  • Authors

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    Source

    American journal of epidemiology 181:7 2015 Apr 01 pg 488-95

    MeSH

    Adult
    Aged
    Case-Control Studies
    Confidence Intervals
    Confounding Factors (Epidemiology)
    Female
    Humans
    Logistic Models
    Male
    Middle Aged
    Nails
    New England
    Odds Ratio
    Protective Factors
    Risk Factors
    Selenium
    Smoking
    Urinary Bladder Neoplasms

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural
    Research Support, N.I.H., Intramural
    Research Support, U.S. Gov't, Non-P.H.S.

    Language

    eng

    PubMed ID

    25776013

    Citation

    Beane Freeman, Laura E., et al. "Is the Inverse Association Between Selenium and Bladder Cancer Due to Confounding By Smoking?" American Journal of Epidemiology, vol. 181, no. 7, 2015, pp. 488-95.
    Beane Freeman LE, Karagas MR, Baris D, et al. Is the inverse association between selenium and bladder cancer due to confounding by smoking? Am J Epidemiol. 2015;181(7):488-95.
    Beane Freeman, L. E., Karagas, M. R., Baris, D., Schwenn, M., Johnson, A. T., Colt, J. S., ... Silverman, D. T. (2015). Is the inverse association between selenium and bladder cancer due to confounding by smoking? American Journal of Epidemiology, 181(7), pp. 488-95. doi:10.1093/aje/kwu324.
    Beane Freeman LE, et al. Is the Inverse Association Between Selenium and Bladder Cancer Due to Confounding By Smoking. Am J Epidemiol. 2015 Apr 1;181(7):488-95. PubMed PMID: 25776013.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Is the inverse association between selenium and bladder cancer due to confounding by smoking? AU - Beane Freeman,Laura E, AU - Karagas,Margaret R, AU - Baris,Dalsu, AU - Schwenn,Molly, AU - Johnson,Alison T, AU - Colt,Joanne S, AU - Jackson,Brian, AU - Hosain,G M Monawar, AU - Cantor,Kenneth P, AU - Silverman,Debra T, Y1 - 2015/03/15/ PY - 2015/3/18/entrez PY - 2015/3/18/pubmed PY - 2015/5/23/medline KW - bladder cancer KW - case-control study KW - selenium KW - smoking SP - 488 EP - 95 JF - American journal of epidemiology JO - Am. J. Epidemiol. VL - 181 IS - 7 N2 - Selenium has been linked to a reduced risk of bladder cancer in some studies. Smoking, a well-established risk factor for bladder cancer, has been associated with lower selenium levels in the body. We investigated the selenium-bladder cancer association in subjects from Maine, New Hampshire, and Vermont in the New England Bladder Cancer Case-Control Study. At interview (2001-2005), participants provided information on a variety of factors, including a comprehensive smoking history, and submitted toenail samples, from which we measured selenium levels. We estimated odds ratios and 95% confidence intervals among 1,058 cases and 1,271 controls using logistic regression. After controlling for smoking, we saw no evidence of an association between selenium levels and bladder cancer (for fourth quartile vs. first quartile, odds ratio (OR) = 0.98, 95% confidence interval (CI): 0.77, 1.25). When results were restricted to regular smokers, there appeared to be an inverse association (OR = 0.76, 95% CI: 0.58, 0.99); however, when pack-years of smoking were considered, this association was attenuated (OR = 0.91, 95% CI: 0.68, 1.20), indicating potential confounding by smoking. Despite some reports of an inverse association between selenium and bladder cancer overall, our results, combined with an in-depth evaluation of other studies, suggested that confounding from smoking intensity or duration could explain this association. Our study highlights the need to carefully evaluate the confounding association of smoking in the selenium-bladder cancer association. SN - 1476-6256 UR - https://www.unboundmedicine.com/medline/citation/25776013/Is_the_inverse_association_between_selenium_and_bladder_cancer_due_to_confounding_by_smoking L2 - https://academic.oup.com/aje/article-lookup/doi/10.1093/aje/kwu324 DB - PRIME DP - Unbound Medicine ER -