Incidence trends in bladder and lung cancers between Denmark, Finland and Sweden may implicate oral tobacco (snuff/snus) as a possible risk factor

Otto Hemminki,Börje Ljungberg,Kari Hemminki,Asta Försti,Akseli Hemminki

doi:10.1186/s12885-021-08371-w

Abstract

BackgroundThe dominant risk factor for urinary bladder cancer has been cigarette smoking, but, as smoking prevalence is decreasing in many populations, other risk factors may become uncovered. Such new risk factors could be responsible for halting the declining incidence of bladder cancer. We hypothesize that snuff use by Swedish men may increase the rate for bladder cancer, as snuff contains carcinogenic nitrosamines.MethodsWe carried out an ecological study by comparing incidence trends in lung and bladder cancers between Danish, Finnish and Swedish men in order to test if the Swedish bladder cancer rate deviates from the Danish and Finnish ones. We used the NORDCAN database for cancer data from 1960 through 2016 to test the hypothesis.ResultsIn the three countries, the incidence of lung cancer started to decrease after a peak incidence, and this was later followed by declining incidence in bladder cancer in Denmark from 1990 to 2016 by 14.3%, in Finland by 8.3% but not in Sweden (the decline of 1.4% was not significant). The difference in trends can be partly explained by the increasing incidence in Swedish men aged 70 or more years. Sweden differs from the two other countries by low male smoking prevalence but increasing use of snuff recorded by various surveys.ConclusionThe stable bladder cancer trend for Swedish men was opposite to the declining trends in Denmark, Finland and globally. We suggest that this unusual finding may be related to the increasing use of snuff by Swedish men. Average users of snuff are exposed to at least 3 times higher levels of carcinogenic tobacco-specific nitrosamines than a smoker of one daily pack of cigarettes.

Highlights

The incidence trends of lung and urinary bladder cancers have marked the cigarette smoking epidemic which started in various countries before or after World War II [1, 2]
Lung cancer rates for Danish and Finnish men decreased slower but, in contrast to Swedish men, they did not take up the habit of oral tobacco use
The highest incidence in lung cancer was recorded for Finland, reaching a maximum around 1970

Summary

Introduction

The incidence trends of lung and urinary bladder cancers have marked the cigarette smoking epidemic which started in various countries before or after World War II [1, 2]. A unique aspect of smoking habits among Swedish men is that their smoking prevalence decreased earlier than in other European countries, resulting in the lowest lung cancer incidence at least since 1980 [17, 18]. Lung cancer rates for Danish and Finnish men decreased slower but, in contrast to Swedish men, they did not take up the habit of oral tobacco (snuff, locally called ‘snus’) use. The dominant risk factor for urinary bladder cancer has been cigarette smoking, but, as smoking prevalence is decreasing in many populations, other risk factors may become uncovered. We hypothesize that snuff use by Swedish men may increase the rate for bladder cancer, as snuff contains carcinogenic nitrosamines

Methods

Results

Conclusion