Lung function in smokers - Aspects on COPD diagnosis and associations to atherosclerosis and alcohol consumption

Smoking is the most common and important risk factor for reduced lung function. Chronic Obstructive Pulmonary Disease (COPD) affects mainly smokers and is characterized by airflow obstruction, assessed using one of two major diagnostic spirometric criteria. Aspects of lung function besides spirometry in smokers fulfilling none, either or both of the spirometric criteria for COPD are not well known. Early COPD is hard to reveal, as spirometry has a poor relationship to symptoms. A promising method for early diagnosis of COPD is Impulse Oscillometry System (IOS). Reduced lung function (measured with spirometry) and COPD is associated with cardiovascular disease in a not completely understood way. Smoking is associated with elevated alcohol consumption, but the potential association between lung function and alcohol consumption is unclear.
The aim of this thesis was to analyse extensive lung function tests in a population withmany smokers with light or no decrease in lung function with special reference to COPD diagnosis and association to atherosclerosis and alcohol consumption.
From a previous population-based respiratory questionnaire survey 450 subjects were recruited (never-smokers and smokers, with/without self-reported COPD) and examined with spirometry, body plethysmography, diffusing capacity for CO (DL,CO), IOS and ultrasonography of the internal carotid artery. They also answered questionnaires and
blood samples were collected.
The results show differences in DL,CO, residual volume and respiratory symptoms between subjects fulfilling none, either or both of the diagnostic spirometric criteria for COPD in use. (paper I). Pulmonary resistance is higher in symptomatic subjects, irrespective of a spirometric COPD diagnosis or not (paper II). Subjects with atherosclerotic plaques in the ICA have lower DL,CO and higher residual volume than subjects without plaques(paper
III). Among smokers, heavy drinking is associated with lower DL,CO and forced expiratory volume in one second (FEV1) (paper IV).
In conclusion, this thesis shows that other aspects of lung function in smokers than FEV1 are of value in both COPD diagnosis and in understanding associations to atherosclerosis and alcohol consumption.