Abstract
BackgroundControl selection is a major challenge in epidemiologic case-control studies. The aim of our study was to evaluate using hospital versus neighborhood control groups in studying risk factors of esophageal squamous cell carcinoma (ESCC).Methodology/Principal FindingsWe compared the results of two different case-control studies of ESCC conducted in the same region by a single research group. Case definition and enrollment were the same in the two studies, but control selection differed. In the first study, we selected two age- and sex-matched controls from inpatient subjects in hospitals, while for the second we selected two age- and sex-matched controls from each subject's neighborhood of residence. We used the test of heterogeneity to compare the results of the two studies. We found no significant differences in exposure data for tobacco-related variables such as cigarette smoking, chewing Nass (a tobacco product) and hookah (water pipe) usage, but the frequency of opium usage was significantly different between hospital and neighborhood controls. Consequently, the inference drawn for the association between ESCC and tobacco use did not differ between the studies, but it did for opium use. In the study using neighborhood controls, opium use was associated with a significantly increased risk of ESCC (adjusted OR 1.77, 95% CI 1.17–2.68), while in the study using hospital controls, this was not the case (OR 1.09, 95% CI 0.63–1.87). Comparing the prevalence of opium consumption in the two control groups and a cohort enrolled from the same geographic area suggested that the neighborhood controls were more representative of the study base population for this exposure.Conclusions/SignificanceHospital and neighborhood controls did not lead us to the same conclusion for a major hypothesized risk factor for ESCC in this population. Our results show that control group selection is critical in drawing appropriate conclusions in observational studies.
Highlights
Case-control studies are the design of choice in studying less common diseases such as esophageal cancer
A total of 130 esophageal squamous cell carcinoma (ESCC) cases and 260 hospital-based controls were enrolled in the pilot phase of the study, while the corresponding numbers of cases and neighborhood controls in the main phase of the study were 300 and 571, respectively
The results showed that in the analysis of the 430 cases and 570 neighbourhood controls, after adjusting for the confounding factors, using opium had a significant association with ESCC (OR = 2.05, 95% confidence Intervals (CI) 1.43– 2.93) while in the analysis of the 430 cases and 260 hospital controls, it did not (OR = 0.87, 95% CI 0.57–1.33)
Summary
Case-control studies are the design of choice in studying less common diseases such as esophageal cancer. Consortia of cohorts can help to have enough numbers of cases, case-control studies are still widely used to study the etiology of esophageal cancer. Neighborhood and hospital-based controls have been used in many studies Each of these controls has advantages and disadvantages. Enrolling hospital controls is usually more convenient and less costly, and information collected from cases and controls is more comparable in the sense that both cases and controls respond in a medical setting, but it has the disadvantage that cases and controls may not be from the same study base and the referral pattern for the disease of interest may be different. The aim of our study was to evaluate using hospital versus neighborhood control groups in studying risk factors of esophageal squamous cell carcinoma (ESCC)
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