Researchers from the School of Public Health-Bloomington and Medical School make their case in a letter to the editor of Allergy.

In their recent letter to the editor of leading journal Allergy, Indiana University faculty in the School of Public Health-Bloomington (SPH-B) and the School of Medicine challenge conventional knowledge about measuring the relationship between infant allergy sensitization and risk of childhood asthma. The letter, “Impact of time-varying confounders on the association between early-life allergy sensitization and the risk of current asthma: a post-hoc analysis of a birth cohort,” describes their use of marginal structural models (MSM) to analyze data—rather than generalized estimating equations (such as longitudinal statistical models) commonly used in the field.

"Existing literature on the relationship between early-life (first year of life) allergy sensitization and risk of childhood asthma is mixed," says lead author Arthur Owora, SPH-B Gallahue Family Professor in Child Development. "It is unclear if early-life allergen avoidance prevents or merely delays the onset of current asthma into adolescence or adulthood. Our findings highlight the need for appropriate statistical control for time-varying confounders to inform causal inference and provide support for the avoidance of early-life allergen asthma triggers as a strategy to reduce risk of childhood asthma."

Co-authors include Rui Li, a PhD student in the SPH-B Department of Epidemiology and Biostatistics, and Robert S. Tepper, Mary Agnes Kennedy Weinberg Professor of Pediatrics in the School of Medicine. Investigators from the University of British Columbia, Dalhousie University, the Health Sciences Centre Foundation, the Children’s Hospital Research Institute of Manitoba, and the University of Manitoba also contributed to the letter.

"Results from Dr. Owora’s letter are significant both in terms of informing the science and illustrating the strengths of more complex causal modeling approaches," says Dr. Douglas Landsittel, chair of the SPH-B Department of Epidemiology and Biostatistics. "Moving forward, statisticians, epidemiologists, and other researchers should continue to apply these methods for time-varying confounding in other significant public health issues."

This work was part of the Canadian Asthma Primary Prevention Study (CAPPS), described as a "multifaceted intervention designed to decrease exposure in the first year of infancy to indoor aeroallergens such as house dust mites and pets and to encourage prolonged breastfeeding and delayed introduction of milk and solid foods."

Learn more about Allergy, the leading journal on allergy research, at bit.ly/2lhgSTW. News about SPH-B is always available at go.iu.edu/48bx.