Background: Birth weight (BW) is an important factor for determining the development of the respiratory system. The majority of research analyzed the impact of BW on lung function in youth. BW influence and smoking on lung function in adults with asthma and COPD is an interesting issue.
Objectives: The aim of the study was to investigate relationships between BW, smoking, and lung function in adult healthy individuals and diagnosed with asthma or COPD.
Material and methods: Four hundred seventy-nine subjects were divided into 5 groups: 123 healthy non-smokers, 180 healthy smokers, 72 non-smoking asthmatics, 57 smoking asthmatics, and 47 COPD patients. Relationships between 4 BW quartiles and lung function was analyzed with respect to smoking.
Results: Impact analyzes of BW, smoking, and asthma on FVC% revealed that asthma is the only significant differentiating factor in this spirometric parameter (p < 0.01). FEV1% was significantly influenced by asthma and BW, and FEV1/ FVC% was exclusively influenced by asthma. Spirometric parameters increased proportionally to particular BW quartiles in healthy non-smokers group; however optimal BW quartile predicting increase of parameters was 2751-3250 g. In asthma, BW quartile predicting the increase of spirometric parameters was 3251-3750 g, but BW quartile predicting decrease of FEV1/FVC% was 2751-3250 g. The comparison of results between COPD group and results from other 4 groups showed that values of all parameters in patients with COPD did not change proportionally to all quartiles of BW. In terms of FEV1/FVC%, the proportional increase of parameter in BW quartile 2751-3250 g was observed.
Conclusions: BW, as independent factor influences on spirometric parameters of healthy individuals, patients with asthma, COPD in a differentiated manner depending on quartile of BW rather than on simple linear increase of BW, regardless of smoking.
Keywords: COPD; asthma; birth weight; lung function; smoking.