The impact of modifiable risk factor reduction on childhood asthma development

Abstract

Childhood asthma is responsible for significant morbidity and health care expenditures in the United States. The incidence of asthma is greatest in early childhood, and the prevalence is projected to continue rising in the absence of prevention and intervention measures. The prevention of asthma will likely require a multifaceted intervention strategy; however, few randomized controlled trials have assessed such approaches. The purpose of this review was to use previous meta-analyses to identify the most impactful risk factors for asthma development and evaluate the effect of risk factor reduction on future childhood asthma prevalence. Common and modifiable risk factors with large effects included acute viral respiratory infections, antibiotic use, birth by cesarean section, nutritional disorders (overweight, obesity), second hand smoke exposure, allergen sensitization, breastfeeding, and sufficient prenatal vitamin D level. Evaluation and estimates of risk factor modification on populations at risk should guide scientists and policymakers toward high impact areas that are apt for additional study and intervention.

Keywords: Asthma; Pediatrics; Risk factors.

Fig. 1

Association of risk factors for asthma development within age exposure windows. The four age exposure windows are prenatal, 0–1, < 5, and 5–13 years. Odds ratios and 95% confidence intervals are shown ranked by effect size and directionality. References used to determine point estimates for this figure: smoking, secondhand [69]; gas stove cooking [96]; physical activity, inadequate [64]; pets, cats [57]; probiotics [97]; omega-3 fatty acids [98]; H. pylori [99]; pets, dogs [57]; food sensitization, ≤ 2 years [77]; rhinovirus induced wheezing, ≤ 3 years [24]; obesity [65]; overweight [65]; traffic pollution [100]; allergic rhinitis, mold [101]; fruit intake, adequate [102]; vegetable intake, adequate [102]; RSV infection, infant [23]; acetaminophen, infant [103]; antibiotic use, infant [45]; breastfeeding [88]; smoking, prenatal [70]; infection, antenatal [104]; prenatal maternal stress [105]; acetaminophen, prenatal [103]; antibiotic use, prenatal [44]; cesarean section [37]; preterm delivery [106]; folic acid, maternal [107]; vitamin E, maternal intake [92]; vitamin D, sufficient in utero level [108]

Fig. 2

Population attributable fraction (PAF) among selected risk factors. PAF, the proportion of cases that are attributable to a risk factor and could be prevented by modifying or eliminating the risk factor, is shown on the y-axis. The x-axis represents the risk factor exposure prevalence. The points on the graph reflect the relationship of exposure prevalence and PAF. The PAF is dependent on the prevalence of exposure and its odds ratio for asthma. The size of the points are proportional to prevalence. Odds ratios from meta-analyses were used to estimate PAF (Additional file 1: Table S1 and Fig. 1). References used to determine exposure prevalence for this figure: smoking, secondhand [71]; gas stove cooking [109]; physical activity, inadequate [110]; pets, cats [111]; probiotics [112]; omega-3 fatty acids [112]; H. pylori [113]; pets, dogs [111]; food sensitization, ≤ 2 years [114]; rhinovirus induced wheezing, ≤ 3 years [29, 30]; obesity [61]; overweight [115]; traffic pollution [116]; allergic rhinitis, mold [117]; fruit intake, adequate [118]; vegetable intake, adequate [118]; RSV infection, infant [28]; acetaminophen, infant [119]; antibiotic use, infant [42]; breastfeeding [87]; smoking, prenatal [72]; infection, antenatal [41]; prenatal maternal stress [120]; acetaminophen, prenatal [121]; antibiotic use, prenatal [41]; cesarean section [72]; preterm delivery [72]; folic acid, maternal [122]; vitamin E, maternal intake [123]; vitamin D, sufficient in utero level [124]

Fig. 3

Impact of reducing selected risk factor exposure on asthma cases among children 5–11 years of age. Based on an asthma prevalence of 9.6% from the Centers for Disease Control and Prevention to estimate 2,761,000 children with asthma. Twelve risk factors were selected for ranking based on their effect size, prevalence of exposure, and potential for modification. This figure considers only the main effect of the risk factor (without accounting for potential interactions)