The interaction between family history of COPD, personal smoking and post-bronchodilator airflow obstruction: A cohort study

Abstract

Rationale: The aetiology of COPD is multifactorial, but the independent and combined associations of a personal smoking and family history (FH) of COPD are rarely reported Aim: To examine the role of FH of COPD in predicting post-bronchodilator (BD) airflow obstruction in middle-age Methods: Post-BD spirometry (n=1,389) was used from the 37 year follow-up of the Tasmanian Longitudinal Health Study (TAHS) cohort, when participants were middle-aged. FH of COPD was defined by an affirmative response to questions encompassing 'Has any close biological relative ever had self-reported, doctor-diagnosed or died from COPD, COAD, chronic bronchitis or emphysema?' Multivariable regression models were used and interactions examined. Results: One third of participants reported a FH of COPD (n=462, 34%). The effect of personal smoking was modified by FH of COPD when assessed by post-BD FEV1/FVC (p-value for interaction 0.015): Smokers of at least 10 pack-years with a FH of COPD had a lower post-BD FEV1/FVC by more than half a standard deviation, which approximated an absolute reduction in FEV1/FVC of 5%. This was significantly greater than the estimate for those without a FH of COPD. | Post-BD FEV1/FVC (z-scores [95%CI]) | || | FH of COPD, emphysema ± chronic bronchitis | | Personal smoking | No | Yes | | | Never-smoker | Reference | +0.14 [-0.04 to +0.3] | | | Ever-smoker | | | | | < 10 pack-years | −0.09 [−0.3 to +0.1] | +0.04 [−0.2 to +0.3] | | | ≥ 10 pack-years | −0.36 [−0.5 to −0.2]\***| | −0.59 [−0.8 to −0.4]\***| | \***|p<0.001 | Conclusion: A FH of COPD augments the adverse effect of personal smoking on lung function. Public health messages should highlight this extra risk.