Childhood Asthma: Risk and Protective Factors

1. Childhood Asthma: Risk and Protective Factors Paul Kubic, M.D.

2. 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

3. 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

4. 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

5. 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

6. 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.

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

8. Obesity • Independent risk factor for asthma (white > black?) • Associated with poor small airway scores on PFT’s • Increasing asthma symptoms in teenage females with obesity

9. Inciters of Acute Asthma • Exercise: duration, intensity • Weather changes: temp., relative humidity, barometric pressure, allergens, etc. • Emotional upset, depression associated with persistent asthma > acute asthma

10. 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.

11. Non Specific Risk Factors

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

13. 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)?

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

15. 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”