Interaction effect of psychological distress and asthma control on productivity loss?

Little is known about the potential synergistic effect of comorbid psychological distress (PD) and uncontrolled asthma (UA) on productivity loss. We estimated the productivity loss associated with the combination of these two potentially preventable conditions in employed adults with asthma. A population-based random sample of 300 adults with asthma in British Columbia, Canada, was prospectively recruited between Dec 2010 and Aug 2012. PD and productivity loss due to absenteeism and presenteeism was measured using validated instruments, and asthma control was ascertained using 2010 Global Initiative for Asthma management strategy. We used two-part regression models to study the contribution of UA and PD to productivity loss. Compared with reference group (controlled asthma (CA)+noPD), those with UA+noPD had CAD$ 286 (95%CI $276-297) weekly productivity loss, and those with CA+PD had CAD$465 ($445-485). Those with UA+PD had CAD$449 (437-462) in productivity loss. There was no significant interaction effect of PD with asthma control levels on productivity loss (p=0.22). In patients without PD, uncontrolled asthma was associated with a higher productivity loss than controlled asthma, but this was not the case in patients with PD. This finding can be explained by the fact that the contribution of PD to productivity loss is so large that there is no room for synergy with asthma control. Future studies should assess the impact of interventions that modify PD in patients with asthma.