Abstract
BackgroundSince updated population registers do not exist in many countries it is often difficult to sample valid population controls from the study base to a case-control study. Use of patient controls is an alternative option if the exposure experience under study for these patients are interchangeable with the experience for population controls. Patient controls may even be preferable from population controls under certain conditions. In this study we examine if colon cancer patients can serve as surrogates for proper population controls in case-control studies of occupational risk factors.MethodsThe study was conducted from 1995 to 1997. Incident colon cancer controls (N = 428) aged 35–69 years with a histological verified diagnosis and population controls (N = 583) were selected. Altogether 254 (59%) of the colon cancer controls and 320 (55%) of the population controls were interviewed about occupational, medical and life style conditions.ResultsNo statistical significant difference for educational level, medical history or smoking status was seen between the two control groups. There was evidence of a higher alcohol intake, less frequent work as a farmer and less exposure to pesticides among colon cancer controls.ConclusionsUse of colon cancer controls may provide valid exposure estimates in studies of many occupational risk factors for cancer, but not for studies on exposure related to farming.
Highlights
Since updated population registers do not exist in many countries it is often difficult to sample valid population controls from the study base to a case-control study
The proportion of heavy alcohol drinkers was higher for colon cancer controls than for population controls
No statistical significant difference was seen between the two control groups for diseases such as asthma, dermatitis, and obesity, the estimated odds ratios (ORs) for obesity was above unity (1.4, 95% confidence intervals (CIs) (0.9–2.2))
Summary
Since updated population registers do not exist in many countries it is often difficult to sample valid population controls from the study base to a case-control study. Use of patient controls is an alternative option if the exposure experience under study for these patients are interchangeable with the experience for population controls. In this study we examine if colon cancer patients can serve as surrogates for proper population controls in case-control studies of occupational risk factors. Since good quality population registries do not exist in many countries, patient controls are often used to provide exposure data from the study base in case-control studies [1,2]. Even where good population registries exist, low response rates for population controls may make patient controls an attractive alternative.
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