Chronic Obstructive Pulmonary Disease Steven Markowitz, Problem-Based Exercises for Environmental Epidemiology, Office of Global and Integrated Environmental Health, World Health, WHO/EHG/98.2, Geneva, 1998,

Salvi & Barnes. Chronic obstructive pulmonary disease in non-smokers. Lancet 2009; 374: Proportion of patients with chronic obstructive pulmonary disease (COPD) who are non-smokers worldwide.

Question 1. What are some of the other known or suspected causes of COPD? – Genetic conditions, such as alpha 1 anti-tripsin deficiency – Occupational exposures – Ambient air pollution – Environmental tobacco smoke

Salvi & Barnes. Lancet 2009; 374:733

Proportion of households using biomass fuel for cooking worldwide

Question 2. What study design could be used to study this question? Which would you choose? – Case control study given: Exploratory nature of study Long latency of COPD Difficulty in finding cohorts that differ only (or principally) by type of cooking fuel Limited expense and resources needed

Question 3. How would you select controls? – Controls selected from inpatient surgical and gynecological services and general medical outpatient clinics – Matched on ae and hospital – Excluded if they had history of COPD or Lung Cancer – All underwent lung function testing

Question 4. How would you assess the exposure of cases and controls to indoor smoke? Note: need to assess both current and historical smoke exposure Questionnaire: – Type of cooking fuel – Dwelling construction – Number of rooms – Location of cooking stove (same or separate building) – Hours pent per day cooking Home visits: – Validate information from questionnaire for current exposure Personal monitoring? – Current exposure only

Question 5. What other exposures would you like to gather information on? How would you do it? Potential confounders or effect modifiers: – Cigarette smoking – Environmental tobacco smoke – Occupational exposures – Outdoor air pollution – Genetic factors (family history)

Question 6. Should the investigators collect more cases and/or controls? Is it likely they will be able to address all the variables of interest?

Question 7. Set up the appropriate 2 x 2 tables and calculate the relative risk and 95% confidence interval. Interpret you findings.

Question 8. How do you interpret these results?

Table 3. Odds ratios and confidence intervals for the same variables shown in Table 1, only now adjusted for each other and age and hospital Table 1. Summary of unadjusted odds ratios and confidence intervals Question 9. Interpret the results in Table 3, Do they differ from the results in Table 1? Why or Why not?

Question 10. Calculate the etiologic fraction of COPD in this population attributable to using wood as a cooking fuel. Interpret its meaning. Etiologic Fraction or Attributable Fraction We would expect a 64% reduction in COPD in this population if we were able to eliminate using wood as a cooking fuel.