Cigarette smoking and cancer incidence risk in adult men: National Health Insurance Corporation Study

Abstract

We analyzed risk while adjusting for age, body mass index, frequency of moderate physical activity, alcohol consumption, preference for vegetables versus meats, and frequency of meat consumption in a multivariate analysis and based our findings on not mortality data but incidence data. 733,134 Korean men who were 30 years old or older, insured by the National Health Insurance Corporation, and had a medical evaluation in 1996 were included in the study and followed up through 2000. During the 4-year follow-up period of 3,590,872 person–years, we identified 7204 new cases. We used the Cox proportional hazards model to estimate adjusted relative risks (aRRs), 95% confidence intervals (CIs). The association of current cigarette smoking was significantly stronger as compared with never smokers; aRR was 1.49 (95% CI = 1.39–1.59) for all cancers, 4.46 (2.32–8.57) for esophageal, 3.83 (2.97–4.94) for lung, 3.01 (1.58–5.72) for laryngeal, 2.24 (1.48–3.39) for urinary bladder, 1.62 (1.42–1.84) for gastric, 1.75 (1.12–2.74) for oral and pharyngeal, 1.58 (0.97–2.27) for pancreatic, and 1.50 (1.29–1.74) for liver cancer. Our findings, based on incidence data, confirmed that differences in smoking habit were responsible for most of the differences observed in smoking-related cancers.

Introduction

Epidemiologic studies have consistently shown an association between smoking and cancer of the lung, larynx, mouth, esophagus, urinary bladder, kidney, pancreas, and cervix [1], [2], [3], [4], [5], [6], [7]. Several reports also suggest an association between smoking and cancer of the stomach, liver, colon, and rectum [8], [9], [10]. Most large cohort studies collect detailed smoking histories, but variable information on other potential risk factors. Consultants for the tobacco industry have speculated that confounding may cause studies to exaggerate the risks attributed to smoking [11], although there is little evidence that this is occurs. Recently, US Cancer Prevention Study (CPS) II suggested that multiple covariates had little impact on the relative and attributable risk for cancer mortality after adjustments were made for age and sex [12]. Since that study was based on cancer mortality data, the effect of smoking on cancer incidence may have been confounded by its effect on other fatal diseases, such as cardiovascular disease [13]. Fewer large prospective studies have assessed the disease risks associated with smoking in Asia, where the widespread consumption of manufactured cigarettes began more recently than in North American and Northern Europe. Our study has the additional strengths of being able to measure cancer incidence, which is informative for sites with higher survival rates, and ability to control for several other major potential risk factors. It is uncertain whether the CPS II results are applicable to groups with different genetic and environmental backgrounds [11], [14].

In Korea, the National Health Insurance Corporation (NHIC) has been providing health insurance to government employees and teachers since 1980 along with biennial health examinations that include height, weight, and blood pressure measurements, chest radiography, blood counts, and blood chemistries. In addition, a self-administered questionnaire collects information regarding medical history, current health status, and individual life styles regarding tobacco and alcohol consumption, dietary preferences, and leisure-time physical activity.

To analysis the association of smoking with the incidence of all cancers and the cancers of major organ sites for age, body mass index, frequency of moderate physical activity, alcohol consumption, preference for vegetables versus meats, and frequency of meat consumption, we performed National Health Insurance cohort study.