Childhood Asthma: Risk and Protective Factors

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Childhood Asthma Risk and Protective Factors

• Paul Kubic, M.D.

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Asthma is a Syndrome with Subtypes

• Genetic factors and environmental exposures
  combine to produce asthma
• Airway inflammation and obstruction are triggered
  mainly by infection, allergens and irritants
• Risk and protective factors alter the response to
  these triggers
• Risk factors are being defined more clearly

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Genetics

• Single asthma gene unlikely
• Family members with allergies or asthma
• Maternal disease poses greatest risk
  statistically
• ADAM-33 is a newly noted asthma associated gene

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Perinatal Problems

• Prematurity and recurrent wheezing are associated
• Chronic lung disease of infancy (BPD) is related
  to later lung abnormalities
• Smoking during pregnancy and low birth weight are
  correlated with asthma

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Allergy

• Up to 80 of persistent asthmatics have evidence
  of allergic sensitivity
• Airborne allergens are more common than foods as
  triggers
• Mold, mite and cockroach are especially important

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Environmental Tobacco Smoke (ETS)

• Cigarette smoke is both inciter and inducer of
  asthma
• Smoke constituents on clothing can enter lungs
  and bloodstream
• Acute exposure especially effects poorly
  controlled asthma
• Other irritant factors wood stove, gas heater,
  outdoor pollution, etc.

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Respiratory Viruses

• Early life RSV, PI, HMPV, IFA, etc. especially
  severe!!
• Immune changes associated with infection increase
  risk of asthma (TH2 gt TH1)
• Viral respiratory infection increases risk for
  allergen sensitization
• Chlamydia, mycoplasma associated with asthma
  (bacteria)

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Obesity

• Independent risk factor for asthma (white gt
  black?)
• Associated with poor small airway scores on PFTs
• Increasing asthma symptoms in teenage females
  with obesity

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Inciters of Acute Asthma

• Exercise duration, intensity
• Weather changes temp., relative humidity,
  barometric pressure, allergens, etc.
• Emotional upset, depression associated with
  persistent asthma gt acute asthma

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Protective Factors

• Bacterial products endotoxin, lypopolysaccharides
  , hygiene hypothesis?
• Prebiotics probiotics data in eczema positive,
  ongoing studies
• Diet antioxidants, vitamin C and E, good
  fats, etc.

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Non Specific Risk Factors
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Pets

• Risky in sensitized families with asthmatics
• Protective for allergic patients without
  asthmatic family members
• Pets bacterial product exposure may be
  protective

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Daycare

• Infection triggered wheezers at risk
• Older siblings in daycare a risk for infant
  wheezers
• Protective as non-sanitized site of bacterial
  exposure (hygiene hypothesis)?

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Breastfed Patients

• Asthmatic breast feeders child at risk?
• Breastfeeding protective for RSV infection
• Duration of breastfeeding associated with
  protection ( gt 4 months)
• Bottle feeding may protect more than short term
  breastfeeding

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Summary of Bronchial Asthma Risks

• Many risks and few protective factors
• Genetics remain of primary importance
• Avoid any cigarette smoke exposure
• Animal exposure may protect in dander negative
  family
• Risk modification may function as future
  controller therapy