Siblings of patients with severe chronic obstructive pulmonary disease have a significant risk of airflow obstruction

Although familial clustering has been described, few studies have quantifie d the risk of airflow obstruction in siblings of patients with chronic obst ructive pulmonary disease (COPD). One hundred fifty-two subjects with airfl ow obstruction and a low gas transfer factor but without PiZ (alpha (1)-ant itrypsin deficiency) were identified and 150 were enrolled in the study. Co mplete data were obtained from 173 of 221 siblings of these subjects. Forty -four of 126 current or ex-smoking siblings had airflow obstruction (FEV1/F VC < 0.7) and 36 also had a FEV1 < 80% predicted, in keeping with COPD. One hundred eleven current or ex-smoking siblings were matched for age, sex, a nd smoking history with 419 subjects, without a known family history of COP D, from the European Prospective Investigation of Cancer (EPIC)-Norfolk coh ort. The prevalence of COPD was much lower in the EPIC group (9.3%) when co mpared with the siblings (31.5%; odds ratio, 4.70; 95% confidence interval, 2.63 to 8.41). The odds ratio for COPD in siblings with less than a 30 pac k-year smoking history was 5.39 (95% confidence interval, 2.49 to 11.67) wh en compared with matched control subjects. Taken together these results dem onstrate a significant familial risk of airflow obstruction in smoking sibl ings of patients with severe COPD.