STRATEGIES TO ALTER THE NATURAL HISTORY OF CHILDHOOD ASTHMA

FCAAIA Notes: I guess one of the best ways to avoid having asthma is to choose the right parents, as asthma and other allergic disease are more common in children whose parents have allergies.

Of course, as shown in this study air pollution is a big risk factor for the onset and for exacerbations of asthma.  Outdoor air pollution is something over which individuals have little control (think globally; act locally!).  Indoor air pollution is easier to control.  Active and passive smoking are major triggers to allergic airway disease.  Wood stoves, fireplaces, and wood burning stoves are also a big source of indoor air pollution.

Vitamin D is a hot topic in asthma control. Sufficient vitamin D levels appear to be associated with better asthma control (but usually not the only factor).  If your vitamin D level is low, boosting it with vitamin D supplements won’t hurt, even if it doesn’t help much.

There is a big literature about hygiene and germ exposure early in life.  Being a little dirty might not be such a bad thing.

The bottom line is that as physicians we want to do everything we can to maximize the control of your allergic airway symptoms and to use a little medication as is necessary to do so.

(Source: http://www.medscape.com/viewarticle/876429?src=wnl_tp10j_170413_mscpedit&uac=112079PK&impID=1328247&faf=1 April 13, 2017. For Medscape articles: User name: FCAAIA, Password: Allergies. Adapted from: Curr Opin Allergy Clin Immunol. 2017;17(2):139-145)

Abstract

Purpose of review: Asthma exhibits significant heterogeneity in occurrence and severity over the lifespan. Our goal is to discuss recent evidence regarding determinants of the natural history of asthma during childhood, and review the rationale behind and status of major efforts to alter its course.

Recent findings Variations in microbial exposures are associated with risk of allergic disease, and the use of bacterial lysates may be a promising preventive strategy. Exposure to air pollution appears to be particularly damaging in prenatal and early life, and interventions to reduce pollution are feasible and result in clinical benefit. E-cigarette use may have a role in harm reduction for conventional cigarette smokers with asthma, but has undefined short-term and long-term effects that must be clarified. Vitamin D insufficiency over the first several years of life is associated with risk of asthma, and vitamin D supplementation reduces the risk of severe exacerbations.

Summary: The identification of risk factors for asthma occurrence, persistence and severity will continue to guide efforts to alter the natural history of the disease. We have reviewed several promising strategies that are currently under investigation. Vitamin D supplementation and air pollution reduction have been shown to be effective strategies and warrant increased investigation and implementation.

Introduction

Asthma is a developmental disease: the majority of cases are diagnosed by age 6, and lung function abnormalities may be present in early infancy. However, diagnosis in early childhood may be difficult as preschool wheeze has a variety of causes including bronchiolitis. Almost 50% of children report wheeze before age 6, but 40% of these children experience resolution of wheeze between the ages of 3 and 6.

The existence of distinct trajectories of childhood wheeze, and of asthma more generally, represents a challenge to the elucidation of the natural history of the disease. Several phenotypes of preschool wheeze have been identified and indices have been developed to predict the development of subsequent asthma by mid-childhood. Children with preschool wheeze in the Tucson Children’s Respiratory Study cohort were categorized in three groups: early transient wheezers with symptoms by age 3 and resolution by age 6, persistent wheezers with symptoms by age 3 that persisted at age 6 and late-onset wheezers with symptom onset between ages 3 and 6. Approaches employing machine learning computational techniques to distinguish asthma phenotypes have largely corroborated the existence of groups defined by early life wheeze (transient or prolonged), late-onset wheeze and persistent wheeze (controlled or troublesome). This work has led to the identification of major risk factors for persistent wheeze, including atopy, relatively high asthma morbidity in early life and maternal history of asthma.

Although childhood wheeze may resolve by adulthood, lung function abnormalities frequently persist later in life. A recent study demonstrated distinct trajectories of lung function in nearly 700 children with mild-to-moderate asthma followed to an average age of 26 with annual lung function assessments. Four patterns were identified based on forced expiratory volume in 1 second (FEV1) measurements with approximately equal numbers of individuals in each group: normal lung development, normal lung growth with an early decline in lung function, reduced lung growth with no early decline in lung function and reduced lung growth with an early decline in lung function. Risk factors for abnormal longitudinal patterns include maternal smoking, reduced lung function at enrollment, increased airway hyperresponsiveness, vitamin D insufficiency and male sex.

Although additional research is needed to further characterize asthma subtypes and determinants of their courses over the lifespan, there have been advances in strategies to alter the natural history of asthma. In this review, we discuss medical management in early childhood, prevention of smoke and air pollution exposure, modification of microbial exposures and vitamin D supplementation. Other relevant topics reviewed elsewhere in this issue include allergy and viral respiratory infection prevention

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