Study: Illicit Drug Use an Independent Risk Factor for Asthma ICU Admissions

A retrospective Australian study found that illicit drug users were almost four times as likely as nonusers to require intensive care for an asthma exacerbation.

Asthma is dangerous enough on its own, but social factors may drive its risks up even further.

Many asthma deaths are associated with psychosocial factors such as illicit drug use, psychiatric illness, and low socioeconomic status. An Australian team found that asthmatics who also use drugs may require admission to Intensive Care more frequently than those who do not.

Their study retrospectively analyzed the records of patients consecutively admitted for an asthma exacerbation to The Alfred Hospital, a metropolitan tertiary hospital in Melbourne, Australia, during a 5-year period. Results of their analysis were published in Respirology.

Of the 482 consecutive asthma patients admitted to The Alfred Hospital in Melbourne, Australia, from January 2010 to January 2014, 39 were admitted directly to the intensive care unit (ICU). Ten of those 39, or 26%, claimed illegal drug use, compared with only 7% of the group admitted to the ward, or 29 of 443 ward patients (adjusted odds ratio 3.6; confidence interval [CI] 1.33—9.73 P = 0.012).

Among all who used inhaled corticosteroids (ICS), the odds ratio for ICU admission among illicit drug users as compared to non-users was 0.39 (CI: 0.04—4.09; P = 0.43). In contrast, among patients who did not adhere to ICS, the odds ratio for ICU admission for illicit drug users compared with non-users was 8.14 (CI: 2.32—28.54; P = 0.001). Thus, the risk of ICU admission was roughly doubled (from nearly fourfold to eightfold) among illicit drug users who did not adhere to ICS. This doubling of risk led the investigators to postulate that regular use of preventive ICS may be more critical and nonadherence may be more deleterious among illicit drug users than among non-users.

The studied ICU patients were more likely to use marijuana (P = 0.188), heroin (P = 0.398), and other illicit drugs (eg, amphetamines, cocaine, non-prescribed opioids) (P = 0.001) than ward patients. These findings prompted the investigators to speculate that substantial use of illicit drugs may lead to poorer self-management of asthma and that smoking some drugs (eg, methamphetamine) might directly worsen asthma as well.

The ICU group also had a lower mean socioeconomic status (indicated by the postal code of their home address) than the ward group, but after adjustment for other covariates, low socioeconomic status was not found to be a statistically significant risk factor for ICU admission. Moreover, the frequency of having a psychiatric diagnosis was similar in both groups.

Based on their findings, the investigators concluded that, among asthmatics, illicit drug use is an independent risk factor for ICU admission. They recommended that physicians make an active effort to determine illicit drug use when taking the history of a patient with an asthma exacerbation because it may be a useful indicator of the need for intensive monitoring.