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Tobacco smoking and bladder cancer in coffee non-drinkers
  1. C Pelucchi1,
  2. A Tavani1,
  3. E Negri1,
  4. S Franceschi2,
  5. C La Vecchia3
  1. 1Istituto di Ricerche Farmacologiche “Mario Negri”, Via Eritrea 62, 20157 Milan, Italy;
  2. 2Field and Intervention Studies Unit, International Agency for Research on Cancer, 69372 Lyon, Cedex 08, France
  3. 3Istituto di Statistica Medica e Biometria, Università degli Studi di Milano, 20133 Milan, Italy
  1. pelucchi{at}marionegri.it

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Data from a large Italian case-control study confirm that the tobacco related relative risk of bladder cancer is higher in coffee non-drinkers than in coffee drinkers. However, given the correlation between tobacco and coffee, the population attributable risk was similar for coffee drinkers and non-drinkers.

Lopez-Abente and Escolar, using data from a Spanish case-control study, suggested that the association between tobacco smoking and bladder cancer may be stronger among coffee non-drinkers than among usual coffee drinkers.1 This potential favourable interaction has some biological plausibility, and can be related to the inhibition of enzymes involved in the activation of carcinogenic aromatic amines, including cytochrome P4501A2.2

To provide further information on the issue, we analysed data from a case-control study conducted in Italy between 1985 and 1992, whose main results on tobacco and coffee have been published elsewhere.3,4 Briefly, a total of 727 histologically confirmed, incident cases of bladder cancer (617 men, 110 women), aged 27–79 years (median age 63), were included in the study. They were recruited in the National Cancer Institute and in a network of other major general hospitals and university clinics in greater Milan and in Pordenone (north eastern Italy). Controls were 1067 subjects (769 men, 298 women), aged 25–79 years (median age 60), admitted to the same network of hospitals of cases for acute, non-neoplastic, non-urological or genital tract diseases (23% were admitted for surgical conditions, 29% for fractures and traumatic conditions, 18% for non-traumatic orthopaedic disorders, and 30% for miscellaneous other illnesses). Less than 3% of subjects approached (cases and controls) refused the interview.

Data were collected by trained interviewers using a structured questionnaire, including information on sociodemographic factors, personal characteristics and lifestyle habits, history of selected diseases and of relevant occupational exposures. Questions on coffee drinking included average cups drunk per day and duration of use; questions on tobacco included smoking status (never smoker, ex smoker or current smoker), average quantity smoked per day, and duration of the habit. Information on tobacco and coffee was satisfactorily reliable.5 We estimated the odds ratios (OR) and their 95% confidence intervals (CI) using unconditional multiple logistic regression, including terms for age, sex and study centre. Further adjustment for education and occupation did not materially change any of the results.

Table 1 shows the distribution of cases and controls, the corresponding OR and 95%CI according to tobacco smoking in strata of coffee drinking. Among cases, ever smokers were 84% among coffee drinkers and 78% among non-drinkers. Corresponding fractions among controls were 65% and 53%. Compared with never smokers, the OR for current smokers was 3.2 (95%CI 2.3 to 4.4) for coffee drinkers and 5.3 (95%CI 2.5 to 11.4) for non-drinkers. The test for heterogeneity was non significant. The relative risks for current smokers increased at higher levels of cigarettes per day in both coffee drinkers (OR=2.7 for <15, OR=3.8 for ≥15) and non-drinkers (OR=4.6 and 5.5 respectively). Trends in risk were observed in both strata also for duration of the habit, the OR being 3.6 (95%CI 2.6 to 5.1) in coffee drinkers and 6.1 (95%CI 2.8 to 13.6) in non-drinkers for smoking duration >30 years. When the analysis was restricted to 617 male cases and 769 male controls, the OR for current smokers was 3.5 (95%CI 2.4 to 5.2) among coffee drinkers and 4.2 (95%CI 1.7 to 10.4) among coffee non-drinkers.

In conclusion, our study confirms that cigarette smoking is a risk factor for bladder cancer both in coffee drinkers and non-drinkers, and provides some support for the observation that coffee may attenuate the relative risk deriving from tobacco. Still, the population attributable risks were similar in coffee drinkers and non-drinkers. In fact, as coffee and tobacco consumption were positively correlated, risk fractions of bladder cancer attributable to smoking in this Italian population were 56% (95%CI 36% to 77%) among coffee non-drinkers and 53% (95%CI 43% to 64%) among drinkers, confirming the prominent effect of smoking on bladder carcinogenesis in both coffee drinkers and non-drinkers.

Table 1

Distribution of 727 cases of bladder cancer and 1067 controls according to smoking habits, in coffee and non-coffee drinkers, and odds ratios* (OR) and corresponding 95% confidence intervals (CI). Italy, 1985–1992

Acknowledgments

Supported by the Italian Association for Research on Cancer, the Italian League against Cancer, Milan, Italy, and by the Commission of the European Communities (Contract N°: QLKI-CT-2000–00069). We thank Mrs Ivana Garimoldi for editorial assistance.

References

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