Underreporting of cancer in medical surveys: a source of systematic error in cancer research.

Systematic errors occur in the reports of disease frequency derived from health surveys based on questionnaire interviews. Five hundred and thirty-three persons with clinically and histologically confirmed disease in a case-control study of cancer were interviewed in their homes by carefully trained interviewers using a standardized questionnaire interview schedule. Comparisons of the information obtained by interview about past history of cancer with cancer registry and hospital medical record information about the same people revealed serious underestimates of correct frequency and wide variation in the rates of correct reporting. The findings reported here and elsewhere add support to an essential requirement in medical survey research: the completeness and accuracy of responses in health interview surveys must be verified and the methods of verification must be reported before the results can be interpreted with confidence.

The occupation of fishing as a risk factor in cancer of the lip.

To study the role of commercial fishing and related factors in the development of lip cancer, a project that included a case-control study and a cohort analysis was undertaken in Newfoundland. Household survey data were linked with cancer-registry and census data. In comparison with other males, fishermen had a probability of development of lip cancer that was 1.5 times higher (by the case-control method, P less than 0.05) or 4.4 times higher (by cohort analysis, P less than 0.001). Despite the effect of pipe smoking, "outdoorness" and age on the development of lip cancer in general, the occupation of fishing was an additional, independent contribution to the risk. Unexpectedly, using the mouth as a third hand to handle tar-coated nets seemed to protect fishermen from the disease. It was not possible to attribute the higher risk to a particular work activity, nor was a specific responsible carcinogen identified.