Opioids and adverse outcomes in elderly chronic obstructive pulmonary disease patients
We thank D. Viglino and M. Maignan for their interest in our manuscript [1] and for their insightful comments. They raise a valid point that our mortality results may have been influenced by the potentially confounding effects of palliative care receipt on or following the index date. While we excluded individuals receiving palliative care in the year prior to the index date, we did not do so on or after the index date for practical methodological reasons. However, several points should be considered. First, Viglino and Maignan write that the decision to palliate in chronic obstructive pulmonary disease (COPD) often arises in the context of an acute respiratory exacerbation. Our propensity score model included whether or not a recent acute respiratory exacerbation occurred in the 30 days prior to the index date, and opioid users and nonusers were well balanced on that variable after propensity score weighting [1]. Second, increased respiratory-related and all-cause mortality were found not only among users of opioid-only agents but also among users of combination opioid/nonopioid formulations [1]. Opioids combined with paracetamol or aspirin are unlikely to be used for purposes of palliation and such agents represent ~90% of incident opioid use among older adults with COPD [2]. Third, while the possible residual inclusion of individuals receiving palliative care among opioid users may potentially explain the finding of increased mortality, this would be unlikely to explain why risks of outpatient respiratory exacerbations and emergency visits for COPD or pneumonia were also greater among opioid users. If there was residual inclusion of individuals with recent end-of-life decisions among opioid users in our study, this would have been likely to bias the intensive care admission outcome towards being significantly decreased among opioid users, and not rendered a nonsignificant association, as Viglino and Maignan propose.
