Individuals with chronic drug use disorders frequently have medical co-morbidities.1,2 Mertens et al. documented the high prevalence of chronic medical conditions and its associated significant morbidity among insured patients in a specialty alcohol and drug treatment clinic.3 Among alcohol or drug dependent patients on the opposite end of the socioeconomic spectrum in the USA — those without primary care who were entering residential detoxification — 45% reported having a chronic medical illness.1 One third of a comparable group reported being in fair or poor health.4 Thus, it is fair to say that co-morbidity, among the socioeconomic spectrum of chronic drug users in care, is the norm, not the exception.

Despite an expanding literature on medical co-morbidities among drug using populations, respiratory diseases have not been well-studied. The bulk of the literature on drug users and respiratory disease has focused on infectious complications of drug use, including bacterial pneumonia, septic pulmonary embolism, and tuberculosis (TB).5,6 These medical conditions are acute or sub-acute (e.g. TB) episodic illnesses. Chronic, non-infectious respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) among drug users have not been well-characterised. Studies demonstrating the effectiveness of disease management programmes for chronic medical conditions such as asthma typically exclude individuals with drug use.7 However, a better understanding of the risks of chronic respiratory diseases would inform efforts to improve the medical assessment and treatment — both therapeutic and preventive — of patients who are also drug users. Such work would address a treatment gap for a population less likely to receive quality asthma care7 and flu vaccination.8

In this issue of the PCRJ, Palmer et al. report on respiratory diseases in drug users.9 Specifically, they performed a cross-sectional analysis of the association of chronic respiratory diseases and “drug misuse” using administrative data collected from general practices in Scotland. The authors found that drug users were more likely to have a diagnosis of chronic respiratory diseases (i.e. asthma, COPD, and “respiratory system disease”) than a control group matched for age, gender, and economic status. Drug users were also more likely to be prescribed respiratory medications, primarily bronchodilators and inhaled corticosteroids. These associations did not appear to be fully attributable to the high prevalence of tobacco use, since these differences persisted with adjustment for tobacco use. This study's results are consistent with others in the literature,1–4 and Palmer et al. substantively contribute to this literature by performing their analysis on a national database.9 Additionally, the use of a control group matched on key socio-demographic variables strengthens the research design.

Nonetheless, interpretation of study findings requires consideration of study limitations. First, substance type was unknown in nearly three-quarters of cases (72%), making it difficult to assess what accounts for the relationship between drug use and respiratory disease. Second, chronic respiratory disease was defined as ever having a diagnosis of asthma, COPD, or “respiratory system disease” since birth; therefore it is unknown whether the respiratory disease predated the onset of drug use. Third, although the exact number of opioid users in the study is unknown, some portion of the drug “misuser” sample consisted of patients prescribed methadone for opioid dependence from general practices, which may have required frequent office visits; therefore, respiratory diseases may have been more likely to be detected given the increased surveillance among these patients.

Despite these caveats, the study raises useful questions and suggests pragmatic implications. As noted among other studies of drug users, tobacco use in this study's sample9 was almost universal (90%). Although the findings may not have been fully attributable to tobacco use, tobacco is still the major driver responsible for respiratory disease in this population. From a clinical perspective, given that COPD is typically under-diagnosed and under-treated in primary care,10 these findings, although not definitive, should raise awareness that individuals with drug addiction are at high risk of chronic respiratory diseases. From a research perspective, determining whether or not contributors other than tobacco exist would be of value, as it might enable medical teams pro-actively to direct attention to other useful evaluation and treatment.

Evidence of an increased risk of chronic respiratory diseases among drug users also enhances the case for the coordination of care between addiction treatment providers and those addressing these patients’ chronic medical conditions.11 Drug treatment is an opportunity for the patient not only to address drug use but also to consider the wider health consequences of drug use including respiratory illness and linking patients to medical care.12,13 Raising the issue with the patient and making a plan to address this common diagnosis might serve not only to improve their health and quality of life but could build the rationale for the patient to make recovery a priority. Weisner et al. demonstrated improved addiction outcomes with integrated addiction and medical treatment for those with chronic medical conditions.14

This examination of respiratory diseases among drug users9 adds further strength to the premise that, given the frequency of overlapping drug use and medical co-morbidities, improvements in these health domains will likely require health professionals to be cognisant of both, in the quest to address either optimally.