Studies of the familial aggregation of chronic bronchitis and obstructive airways disease.

The familial aggregation of chronic bronchitis and obstructive airways disease was investigated in a propositus population of 430 persons aged 45-54 years and 1340 of their first (1 degree), second (2degrees) and third (3 degrees ) order relatives. All subjects were screened in their homes using a modified British MRC respiratory disease questionnaire and a portable spirometer. 1 degree relatives of propositi with either chronic bronchitis or obstructive airways disease demonstrated up to a two-fold excess prevalence of chronic bronchitis when compared to 1 degree relatives of non-affected propositi. This excess prevalence of chronic bronchitis was independent of sex, cigarette smoking patterns, respiratory illness history, residence in a common household, geographical distribution within the study community and the presence of alpha1-antitrypsin Pi variants. The prevalence of chronic bronchitis in 1 degree relatives of diseased propositi was also greater than in 2 degrees relatives of diseased propositi, in whom the prevalence approximated that of the general population.