Hospital versus population controls in a retrospective study on diet and stomach cancer

Abstract

The aim of the present study is to evaluate drawbacks and advantages of the choice of hospital versus population controls in a case control study on diet and cancer through the analysis of a retrospective study on diet and gastric cancer (GC) conducted in Forli, Italy, involving 232 cases, 430 population controls and 252 hospitalized controls. The present paper reports the comparison of results on diet and GC risk obtained using the 2 types of controls. Population controls tended, in general, to eat all kinds of foods slightly more frequently (bread, pasta, cold cuts, fresh fish, seasoned cheeses, legumes, garlic, onions and preserved fruits), with the exception of cooked vegetables, which were reported less frequently by population than by hospital controls. ORs for specific foods adjusted for confounders and other foods were consistent in the separate models including population and hospital controls respectively for all food groups, with the exception of cooked vegetables which represented a protective factor only when hospital controls were considered (high consumers, population controls: adjusted, OR=0.9, trend p value 0.54; high consumers, hospital controls, adjusted OR=0.5, trend p value <0.01). Hospital controls were slightly less often current smokers (22.6 versus 30.0%) and more often regular wine drinkers (57.5 versus 47.8%) compared with population controls, but none of these variables was associated with GC risk. The main results in this study were consistent using both types of controls, nevertheless the distribution of some dietary variables not related to the disease under study differed between the 2 control groups, suggesting some caution in the use of hospital controls when studying diseases other than GC.