African-Americans’ asthma milder at baseline, but more prone to treatment failure (AJRCCM)

African-Americans have generally worse asthma control than whites. No one knows to what degree this is due to genetic differences between the races (e.g., resulting in differential responses to medications), or socioeconomic differences (e.g., higher exposure to environmental factors like pollution and cockroach antigens; reduced access to care).

Michael Wechsler et al reviewed 1,200 subjects’ records from 10 clinical trials in the Asthma Clinical Research Network. At baseline, African-Americans’ (n=233) asthma appeared easier to control: they reported fewer symptoms and lower rescue inhaler use than whites, and had equal FEV1, bronchial reactivity, quality of life scores, and exhaled nitric oxide concentrations. 

However, out of the 147 treatment failures recorded (defined as systemic corticosteroid use, hospitalization or emergency department visit, prolonged decrease in peak expiratory flow, or increase in rescue albuterol use), more were in African-Americans (20% of the 233) than whites (13% of the 795).

Adherence was equal (90%) in both races among those who had treatment failures, and was only non-significantly lower in African Americans overall.

Authors raise the concern that long-acting beta agonist use could have been the reason for the excess treatment failures in African-Americans. They point out that blacks may have a blunted response to LABAs compared to whites, and that in a 2008 randomized trial, LABAs + inhaled steroids did not improved asthma control in blacks compared to inhaled corticosteroids alone. That doesn’t implicate the LABAs to me, though — it implicates the asthma. If someone has an exacerbation on a useless medication, it doesn’t mean the medication caused the exacerbation.

Of course, LABAs are under suspicion as being worse than useless, in fact harmful. The mechanism hypothesized here for how LABAs enable treatment failures goes like this: African-Americans may tend to underestimate their asthma symptoms and severity compared to other races (although strangely, the study they cite to support this was in Puerto Rican children);  LABAs can blunt sensitivity to asthma symptoms; therefore, LABAs may contribute to treatment failures. (Again, this doesn’t say LABAs make asthma worse, only that they may mask its worsening and that this may be more dangerous in African Americans.)

Socioeconomic factors were not ascertainable from their data. Since the environmental factors associated with lower socioeconomic status may be the driving force behind the observed differences in asthma control between the races, another study would be needed to illuminate that part of this picture.

Wechsler ME et al.  Impact of Race on Asthma Treatment Failures in the Asthma Clinical Research Network. Am J Respir Crit Care Med 2011;184:1247-1253.