The cross-sectional study is retrospective in a sense, as it will allow to collect historical data on smoking, smoking cessation, address socio-demographic and other differentials of smoking. The investigators will also address the relationship of liver disease with COPD. This will be determined based on presence of hepatitis B and C tests (antigens and antibodies), liver enzyme levels and concentration of alpha-1-antitripsine, which is related to the development of COPD. Current or former smokers who had a concomitant diagnosis of asthma will not be excluded in the cross-sectional study. Instead, historical data on whether the participant had been diagnosed with asthma will be collected.