Purpose: We investigated familial aggregation as well as familial covariation of diseases by means of a questionnaire survey dealing with family histories of stomach cancer, stroke, hypertension, diabetes and tuberculosis as well as life style among 2,769 inhabitants of a rural community (84% of census population).
Methods: The strength of familial aggregation was shown by an odds ratio (OR) that compared the number of families in which siblings suffered from one of the above diseases among families in which at least one parent suffered from it, and among families in which neither did. Probands were divided into two groups for analysis: an under-55 "young group," and a 55-and-older "old group."
Results: The OR for stomach cancer was lowest and insignificant in the young group, and significant (2.2, p < 0.05) only in the old group. The OR for stroke, hypertension, and tuberculosis was 4.5-5.1 (p < 0.05) in the young group but decreased to 2.3-3.2 in the old group. Diabetes increased from 3.9 to 5.7 (p < 0.05) with advancing age. Age-related OR trends were not affected by exposure to cigarette smoke in the past. Stomach cancer showed a borderline familial covariation with diabetes and a borderline inverse covariation with hypertension. Hypertension showed a familial covariation with stroke and diabetes.
Conclusions: Among the investigated diseases, familial aggregation was weakest for stomach cancer. The results suggest that stomach cancer may share a common familial etiologic factor with diabetes and hypotension.