A Case-control Study On Risk Factors Of Chronic Obstructive Pulmonary Disease

IntroductionChronic obstructive pulmonary disease is a disease state that characterized by airflow limitation but not fully reversible.The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases.COPD is one of the predominant causes of morbidity and mortality worldwide.According to the WHO,COPD was the 6th cause of mortality in 1990.It is estimated that COPD will be the 3rd cause of mortality and the 5th cause of economic burden of disease by 2020 all over the world.In China,COPD is also a major public health crisis.Respiratory diseases(of which COPD is a major component) are the first and fourth leading cause of death, respectively in rural and urban areas,accounting for 1 million deaths as well as over 5 million disabilities each year.The prevalence of COPD in individuals 40 years of age or older in China is 8.2%.The determinants of COPD include both environmental factors and genetic predispositions.Environmental factors include smoking,occupational exposure to toxic gases,dust and air pollution.The best known genetic factor linked to COPD is a deficiency of the serine proteaseα₁-antitrypsin.Body mass index,nutritional status, childhood and adulthood respiratory problems and socioeconomic status are other important determinants of COPD.COPD induces serious harm to human health, reduces the patient's ability to work and quality of life and inflicts a tremendous financial burden for the family and the community.It is a prerequisite to determine the risk factors of its occurrence for the formulation and implementation preventive measure. A case-control study was conducted to investigate the relative risk factors of COPD and provide the clues for primary prevention of COPD.Subjects and MethodsThis study was a hospital-based case-control study.A uniform questionnaire for cases and controls was used to investigate the medical records.The patients aged 40 to 92 years were recruited from the municipal hospital in Shenyang between Jan of 2003 and Apr of 2006.The patients were diagnosed as COPD according to Global Initiative for Chronic Obstructive Lung Disease(GOLD).COPD stagesâ… -â…£were determined according to the current criteria of GOLD severity.Each patient was matched with a control for age(±3 yrs).The controls,rule out the respiratory diseases,were patients in the same hospital during the same period.The survey included demographic(age,sex), smoking history(duration of smoking,cigarettes per day,age of starting smoking,and quit smoking),laboratory data,drug allergy history and disease severity of COPD patients.The questionnaire was designed by experts of epidemiology and respiratory. Before investigation,the investigators were carried out a short-term training.Ten percent questionnaires were randomly reviewed.The database was established on Epi Info 2002 software.Univariate and multivariate conditional logistic regression analysis and Chi-square trend test were used to calculate the odds ratios(OR) and 95% confidence intervals(CI) by SPSS 13.0 software.ResultsThe 435 patients diagnosed as COPD in this study were matched with 435 controls by age(±3 yrs).The mean ages of patients and controls(mean±S.D.) were 72.21±7.84 years and 70.51±7.65 years,respectively.No significant differences were found between patients and controls in mean age(p＞0.05).Univariate conditional Logistic regression model showed that male(OR=1.802),drug allergy history(OR=4.346), smoking habits(OR=2.857),duration of smoking＞10 years(OR=2.719),cigarettes per day＞10(OR=2.250),age of starting smoking≤20(OR=1.909) and hyperglycemia (OR=2.390) were associated with COPD.The dose-response relationship was examined using Chi-square trend test between the exposure level of smoking and the risk of COPD.The association between risk factors and COPD was significant in men and women.But the higher the exposure level of smoking,the lower the risk exists in male.Female smoker more than ten years and smoked cigarette more than 10 per day had significant higher odds ratios relative to male.Multivariate conditional Logistic regression model in total significant factors showed that the risk factors of COPD would include drug allergy history(OR=4.029),smoking habits(OR=2.635), hyperglycemia(OR=2.390) and male(OR=1.595).ConclusionsIn the present study,gender,drug allergy history,smoking habits and hyperglycemia were risk factors of COPD.A dose-response relationship was found between the risk of COPD and exposure level of smoking.The higher the exposure level of smoking,the greater the risk existed.Female smokers had significant higher odds ratios relative to male.Therefore,to quit smoking,avoid contact with allergens and control blood sugar levels are important to prevent COPD.