Interactions between psychosocial problems and management of asthma: who is at risk of dying?

Adjustment for psychosocial and family problems is common in epidemiological research. Recursive partitioning algorithms, such as CHi Square Automatic Interaction Detection (CHAID), can be used to explore complex interactions between these factors and predictor and outcome variables. We investigated the nature of interactions between asthma management variables and psychosocial problems and how these interactions changed the risk of asthma mortality; 50 cases of asthma death and 201 emergency department controls were recruited. A validated questionnaire was used to collect data. An extended version of CHAID was used to identify statistically significant (p < or = 0.05) interactions controlling for asthma severity. Family problems were associated with increased risk of mortality for patients aged > 31 years (OR = 6.5; 95% CI 2.6-16.1) but not for younger patients. Males were at increased risk overall, but females with family problems (OR = 4.3; 95% CI 1.7-10.7) were at greater risk then males (OR = 3.1; 95% CI 1.2-7.9) with family problems. Alcohol use increased risk of mortality for individuals with verbal instructions (OR = 5.4; 95% CI 1.5-19.5) or without a written action plan (OR = 4.4; 95% CI 1.0-19.4). Individuals with severe asthma and who reported having lung function tests were at increased risk for mortality if family (OR = 8.2; 95% CI 1.6-41.6) or financial problems (OR = 11.5; 95% CI 2.0-65.9) were present. This analysis highlights some important interactions and the magnitude of additional risk for mortality associated with psychosocial or family problems. Psychosocial problems need to be identified and addressed as part of asthma management, because even with best practice, these problems place patients at an increased risk of dying.