Familial related risk-factors in the development of chronic bronchitis/emphysema as compared to asthma assessed in a postal survey

There is a lack of knowledge to which extent heredity or familial risk fact ors are involved in the development of chronic bronchitis/emphysema (CBE). Smoking is regarded as the most important risk factor, but only about 15% o f smokers develop airway obstruction. We evaluated the importance of famili al risk factors compared to smoking and ex-smoking using an epidemiological approach. In 1992, a postal questionnaire was distributed to a study sampl e. In all, 43 questions were asked, in a previously evaluated questionnaire , regarding respiratory symptoms, self-reported lung diseases, smoking habi ts and familial occurrence of chronic bronchitis and asthma. The questionna ire was sent to 12,073 adults living in the southernmost part of Sweden. Th e age range was 20-59 years with an equal gender distribution. The study sa mple was drawn from the population records. The questionnaire was answered by 8469 subjects (70.1%), of whom 392 subjects (4.6%) stated that they had or had had CBE and 469 subjects (5.5%) stated that they had or had had asth ma. In a model with logistic regression using the five explanatory variable s gender, age, familial occurrence for asthma, familial occurrence for CBE and current or ex-smoking the most important risk factors for CBE were fami lial occurrence for chronic bronchitis [Odds ratios (OR): 5.19, 95% confide nce interval (CI): 4.09-6.60, p = 0.000] and current or ex-smoking (OR: 1.7 4, 95% CI: 1.41-2.14, p = 0.000). The most important risk factors for asthm a were familial occurrence for asthma (OR: 3.71, 95% CI: 3.06-4.51, p = 0.0 00) and current or ex-smoking (OR: 1.33, 95% CI: 1.09-1.61, p = 0.004). We have found that familial occurrence for CBE in first degree relatives toget her with smoking is a stronger risk factor for the development of CBE than is smoking.