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Dear Sir,

Gallbladder cancer is a rare but fatal disease. Little is known about the etiology of this disease. Gallstones are a recognized risk factor for gallbladder cancer.1, 2 The effect of alcohol consumption on gallbladder cancer risk remains controversial throughout the published literature.3, 4 In Sweden, people in different occupations have been shown to have different levels of alcohol intake.5 Comparing incidences between occupations with different alcohol consumption could clarify the relationship between alcohol intake and gallbladder cancer risk.

A follow-up study of male workers employed from 1961 to 2000 in Sweden was carried out using data from the Swedish Family-Cancer Database. This Database has been described in more detail previously.6 Briefly, this Database was created to link information from the Multigenerational register, censuses, cancer registries and death notifications; 1.7 million male workers were included in our study. The information on occupations was obtained through the 1960 census. Journalists, waiters, seamen, cooks and stewards had the highest alcohol intake, while farmers and physicians had the lowest.5 These occupations were included in our analyses to make the best evaluation of the alcohol effect on gallbladder cancer. Standardized incidence ratios (SIRs) for gallbladder cancer and 95% confidence intervals (CIs) were estimated by stratifying age and period. SIRs of primary liver cancer for occupational groups with different alcohol consumption were also calculated, assuming that existing differences between those SIRs represent the effect of different alcohol intake on liver cancer risk because other known risk factors for liver cancer, such as infection by hepatitis B or C virus, are low in Sweden.

A decreased risk of primary liver cancer was noted in workers having a lower consumption of alcohol, such as physicians and farmers. An increased risk was observed among occupations with a higher intake of alcohol (i.e., journalists, seamen, waiters, cooks and stewards) (Fig. 1). The data corroborate the association between alcohol consumption and liver cancer risk. For occupational groups with lower alcohol consumption, such as farmers and physicians, a decreased risk of gallbladder cancer was observed, with SIRs of 0.65 (95% CI: 0.56–0.76) and 0.47 (0.09–1.16), respectively. The SIRs for gallbladder cancer associated with occupations with a higher alcohol consumption, such as journalists, and cooks and stewards, were equal to 2.72 (95%CI: 1.35–4.57) and 3.17 (1.51–5.45), respectively. Other occupational groups with a high alcohol intake, such as waiters and seamen, did not show an excessive risk of gallbladder cancer in our study. High levels of physical activity and less obesity among these workers may be protective against the development of gallstones,7, 8 which could be protective for the development of gallbladder cancer. Excessive alcohol intake has been shown to increase the risk of gallstones,9, 10 which is a risk factor for gallbladder cancer. However, the number of gallbladder cancer cases is limited, which may explain some of the wide confidence intervals observed here. The covariation between gallbladder cancer risks and alcohol intake levels suggests that alcohol intake may be a risk factor for gallbladder cancer.

Yours sincerely,

References

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Jianguang Ji, Elisabeth Couto, Kari Hemminki