Exercises: Bias

In a case-control study of smoking and chronic obstructive pulmonary disease (COPD), researchers selected controls from the same hospital as the cases who were diagnosed with COPD. [26] The researchers found a weak association between smoking and COPD. Which of the following are problems with the study (select all that apply):

Which statement is a potential result from selecting both cases and controls from a hospital in a case-control study? (Select all that apply)

In a cohort study of individuals with chronic obstructive pulmonary disease (COPD), it was found that the use of anticholinergic medication (used to treat COPD exacerbations) was associated with increased rates of readmission to hospital.[1] Which of the following biases should be considered when interpreting this finding?