Objectives: The goals were to estimate the year-round burden of health care visits attributable to bronchiolitis and to identify risk factors for bronchiolitis in term healthy infants.
Methods: We conducted a population-based, retrospective cohort study of 103 670 term, non-low birth weight infants enrolled in Tennessee Medicaid in 1995-2003. We monitored infants through the first year of life. Risk factors for bronchiolitis during infancy and rates of inpatient, emergency department, and outpatient visits during the study period were calculated by using claims data.
Results: Over the 9 study years, rates of bronchiolitis visits were 238 outpatient visits per 1000 infant-years, 77 emergency department visits per 1000 infant-years, and 71 hospitalizations per 1000 infant-years. Average annual rates of bronchiolitis visits increased 41%, from 188 visits per 1000 infant-years to 265 visits per 1000 infant-years, from 1996-1997 to 2002-2003. Analysis of the linear trend in 500-g increments demonstrated a negative association between increasing birth weight and bronchiolitis diagnosis. There was a significant negative trend between maternal age and infant bronchiolitis diagnosis. Compared with infants of mothers 20 to 29 years of age, infants of mothers 15 to 19 years of age had a small increase in risk of having a bronchiolitis visit, whereas infants of older mothers (30-39 or 40-44 years of age) were less likely to have a visit.
Conclusions: The disease burden of bronchiolitis is substantial, with increasing rates of all types of visits among term, otherwise-healthy infants enrolled in Tennessee Medicaid between 1995 and 2003. Protective factors in this cohort of term infants included higher birth weight and older maternal age.