Journal of the National Cancer Institute Advance Access originally published online on November 16, 2009
JNCI Journal of the National Cancer Institute 2009 101(22):1553-1561; doi:10.1093/jnci/djp361
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Published by Oxford University Press 2009.
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A Case–Control Study of Smoking and Bladder Cancer Risk: Emergent Patterns Over Time
Affiliations of authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD (DB, JSC, KPC, NR, CS, JL, JFF, RNH, DTS); Department of Community and Family Medicine, Dartmouth Medical School, Hanover, NH (MRK, ASA, RW, AS); Department of Community Health and Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island (CJM, KTK); Maine Cancer Registry, Augusta, ME (CV, MS); New Hampshire Cancer Registry, Concord, NH (SC); Vermont Cancer Registry, Burlington, VT (AJ)
Correspondence to: Dalsu Baris, MD, PhD, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, DHHS, 6120 Executive Blvd, EPS Rm 8008, North Bethesda, MD 20852 (e-mail: barisd{at}mail.nih.gov).
Background: Cigarette smoking is a well-established risk factor for bladder cancer. The effects of smoking duration, intensity (cigarettes per day), and total exposure (pack-years); smoking cessation; exposure to environmental tobacco smoke; and changes in the composition of tobacco and cigarette design over time on risk of bladder cancer are unclear.
Methods: We examined bladder cancer risk in relation to smoking practices based on interview data from a large, population-based case–control study conducted in Maine, New Hampshire, and Vermont from 2001 to 2004 (N = 1170 urothelial carcinoma case patients and 1413 control subjects). We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression. To examine changes in smoking-induced bladder cancer risk over time, we compared odds ratios from New Hampshire residents in this study (305 case patients and 335 control subjects) with those from two case–control studies conducted in New Hampshire in 1994–1998 and in 1998–2001 (843 case patients and 1183 control subjects).
Results: Regular and current cigarette smokers had higher risks of bladder cancer than never-smokers (for regular smokers, OR = 3.0, 95% CI = 2.4 to 3.6; for current smokers, OR = 5.2, 95% CI = 4.0 to 6.6). In New Hampshire, there was a statistically significant increasing trend in smoking-related bladder cancer risk over three consecutive periods (1994–1998, 1998–2001, and 2002–2004) among former smokers (OR = 1.4, 95% CI = 1.0 to 2.0; OR = 2.0, 95% CI = 1.4 to 2.9; and OR = 2.6, 95% CI = 1.7 to 4.0, respectively) and current smokers (OR = 2.9, 95% CI = 2.0 to 4.2; OR = 4.2, 95% CI = 2.8 to 6.3; OR = 5.5, 95% CI = 3.5 to 8.9, respectively) (P for homogeneity of trends over time periods = .04). We also observed that within categories of intensity, odds ratios increased approximately linearly with increasing pack-years smoked, but the slope of the increasing trend declined with increasing intensity.
Conclusions: Smoking-related risks of bladder cancer appear to have increased in New Hampshire since the mid-1990s. Based on our modeling of pack-years and intensity, smoking fewer cigarettes over a long time appears more harmful than smoking more cigarettes over a shorter time, for equal total pack-years of cigarettes smoked.
| CONTEXT AND CAVEATS Prior knowledge Although it is well established that cigarette smoking is associated with risk of bladder cancer, the influence of various parameters of smoking history as well as secular trends in the smoking/bladder cancer relationship were unclear. Study design Odds ratios for bladder cancer risk were calculated in relation to smoking practices learned from interviews among 1170 bladder cancer patients and 1413 control subjects from Maine, New Hampshire, and Vermont in 2001–2004. Odds ratios for the New Hampshire participants of this study were compared with those from two similar case–control studies conducted in 1994–1998 and 1998–2001 in New Hampshire. Contribution Overall, current smokers, compared with never-smokers, had more than a five fold higher risk of bladder cancer. Among New Hampshire residents, there was a statistically significant progressive increase over each time period in bladder cancer risk among both former and current smokers compared with never-smokers. Implications The smoking-related risks of bladder cancer appear to have increased over time, at least among New Hampshire residents. Limitations Time-trend data were unavailable from Maine and Vermont, and there was a 65% participation rate among both cases patients and control subjects, which may have led to an underestimation of estimates of risk. From the Editors
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Manuscript received November 19, 2008; revised August 19, 2009; accepted September 17, 2009.
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  A. J. Alberg and J. R. Hebert Cigarette Smoking and Bladder Cancer: A New Twist in an Old Saga? J Natl Cancer Inst, November 18, 2009; 101(22): 1525 - 1526. [Full Text] [PDF]
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