Table 8.10 shows results from a matched case-control study. A study of acute myocardial infarction (MI) among Navajo Indians matched 144 victims of MI according to age and gender with 144 individuals free of heart disease. Subjects were then asked whether they had ever been diagnosed as having diabetes. For the logistic model, the odds that a subject with diabetes is an MI case equal exp(β) times the odds that a subject without diabetes is an MI case. Estimate exp(β) and explain why the estimate is valid even though the study observed diabetes, conditional on MI status.

Table 8.10 Previous diagnoses of diabetes for myocardial infarction (MI) case-control pairs.

MI Cases MI Controls Diabetes No Diabetes Diabetes 9 16 No Diabetes 37 82 Source: Coulehan et al., Amer. J. Public Health 76: 412–414 (1986), reprinted with permission by the American Public Health Association.