Practical Issues in Asthma Prevention Dr Marie Wheeler General Paediatrician Cheltenham General Hospital/Gloucestershire Hospitals NHS Trust

Outline of discussion Asthma and its prevalence Primary and secondary prevention (Diet, House Dust Mites, pets, smoking) Targeting all this advice.???? Take home messages !!

Asthma in Children… Accurate diagnosis…challenge in children. Education, Education,Education. Asthma guidelines-British Thoracic Society/SIGN Compliance and more education. Advice re. primary and secondary prevention.

Asthma and Allergy 1/3 of 4 year olds with persistent wheeze are sensitive to at least one common aeroallergen. In older children asthma closely associated with allergy with approx. 2/3 affected.

‘’New episodes halved among the 5 to 24 years age group. The issue does not indicate any possible reasons for this.’’ ‘ ’New cases of asthma in children fall by two thirds. The number of new cases of asthma fell significantly in England and Wales between 1996 and 2003, with the number in children falling the most, the latest issue of Social Trends says.’ British Medical Journal March 2005 ….

International Study of Asthma and Allergies in childhood(ISAAC) Burr 25,393 children in 93 schools. CULPRITS FOR WHEEZE Non-metropolitan areas. Active(10%) or passive smoking(6.5%). Presence of a furry pet(5%). Bottled gas, paraffin.-oxides of nitrogen

Primary Prevention  Breast feeding  Smoking  Allergen avoidance-HDM, Pets.

Primary Prevention- Breastfeeding. 8,183 subjects over 4 years ( systematic and meta-analysis) shows protective effect against development in asthma (esp. if FH atopy) Gdalevich. ( A more recent study showed an increase at 6 years.) Wright Breast feeding should be encouraged, its benefits include a protective effect in relation to early life wheezing ( BTS and SIGN guidelines)

Other milks Protein hydrolysate as a supplement or alternative for children who cannot breast feed seems to provide protection.

Smoking

Primary Prevention-Smoking Pregnancy smoking affects infants airway function with increased airway resistance at 4 weeks Young. Increased risk of wheeze is associated with smoking in pregnancy and maternal postnatal smoking.

Smoking In- utero exposure seems to have more impact on childhood lung function Gilliland than post natal smoking..

Smoking Consistent odds ratio for respiratory illness 1.2 to 1.6 for either parent smoking Cook. Odds higher for preschool than school age. Significant effects from paternal smoking too.

Smoking Odds ratio for recurrent or persistent bronchial obstruction in first 2 years of life highest for maternal daily smoking compared with socio-economic factors and atopy. Lodrup, Carlsen, Norway, 802 neonates

Primary Prevention-Allergen Exposure Early exposure to allergens causes sensitization but development of asthma not demonstrated Lau. Considerations given to HDM prevention measures, diet, omega-3 fatty acids, probiotics, H 1 antagonists, immunotherapy, ketotifen.

House Dust Mite- (700,000 hits on google) Dermatophagoides pteronyssinus

David Hide Asthma and Atopy Research Centre-Isle of Wight infants, high risk group, breast fed or extensively hydrolysed formula and HDM prevention manoeuvres (acaricides and mattress covers). Age 8, current wheeze, nocturnal cough, asthma, and atopy all significantly reduced. Environmental manipulation decreased wheeze in first year of life in another high risk group. Custovic

Study of Prevention of Allergy in Children in Europe 2004 Horak >600 high risk newborns. One group- mite-impermeable mattress encasing and simple educational package on allergen avoidance. Control given basic allergy information. At age 2 no difference in HDM sensitization, nocturnal cough, wheezing.

Childhood Asthma Prevention Study-Australia 2004 Peat >600 High Risk Children enrolled (antenatally) Given omega-3 fatty acids and HDM preventative measures. At age 3 significant reduction in cough and HDM sensitization but not wheeze.

House Dust Mite Primary Prevention EVIDENCE CONVINCING? Yes or No?? VOTE

Pets Stay or go? Should we have pets before we have children?

Pets..to stay…to buy… children in Sweden Hesselmar 1999 Children exposed to pets during the first year of life had less allergic rhinitis at age 7-9 and less asthma at age (Increasing no. of siblings associated with less too.)

Pets….to go Prenatal manipulation in high risk for atopy, couples reduced some respiratory symptoms in the first year of life. Cat ownership was significantly associated with sensitization to cats (Custovic A et al,Manchester 2001)

Pet avoidance Primary Prevention EVIDENCE CONVINCING Yes or No?? VOTE

Secondary Prevention  House dust mites-Cochrane reviews..’may’! Pets  Smoking

House dust mites Likes; Warmth Moisture Shedded human skin Carpets Soft furnishings Curtains

House dust mites Dislikes; Ventilation-dehumidifiers Damp dusting HEPA filters Freezers-Soft toys. Barrier covers High temp(>50 degree c) A mite-killing material in a low-temp. wash Acaricidal powder

House Dust Mites-Summary Restricting exposure significantly reduces asthma signs and symptoms ( less days of wheeze, reduced requirement for medication,fewer abnormal peak flows) in some studies. Highly significant reduction in IgE in some studies.

Preventing the allergic march?  Dust mite exposure with bedding encasement was reduced in infants with atopic dermatitis ( who were sensitized to egg, milk or soya bean but not to house dust mite…) ….after 1 year their specific IgE to HDM was lower than controls. Nishioka

But….Costly advice Single bed set, 1 pillow, duvet and mattress covers £ Dehumidifier-e.g £ Air purifier- £ Vacuum cleaners-upright better but cylindrical get to corners! TARGET sensitized PATIENT

Pets;Pets;Pets..stay or go? Can we really reduce cat allergen if the cat goes, or is it too late? Any benefits in buying a cat?

Pets..can we reduce the allergen load? High –Efficiency particulate air (HEPA) cleaner and cat- induced asthma, 35 cat allergic subjects. Wood Measures of cat-allergen levels, symptoms,peak flow, medication,spirometry for 3 months.. Airborne allergens but not settled-dust decreased. No change in measured value of disease activity.

Pets…removal Can take more than 20 weeks for cat removal to affect allergen content in household-dust samples!!.

Removal of cats PEFR improved when high efficiency filter used and less bronchodilator needed at 1 year. Primarily in those with cat sensitivity without their own cat!! Popplewell

Does clinical tolerance really happen? IgG1 and IgG4 were higher in children keeping a cat, but not IgE ( same children ). Hesselmar.Platts-Mills Some children had raised IgG4 but not associated with asthma or sensitization and no IgE antibody to cats. This group had the highest frequency of cat keeping….modified Th2 response but no protective effect.

Pet avoidance Secondary Prevention EVIDENCE CONVINCING Yes or No?? VOTE

Early Treatment of the Atopic Child Study-Southampton 2002 Warner Children with atopic dermatitis between age1-2 treated for 18 months with cetirizine( H1 receptor antagonist) with 18 month follow-up Delay or prevention of asthma in subgroup with AD sensitized to grass pollen, and less so to HDM.

Indoor air pollution-Considerations Nitrogen oxides from gas cookers. Indoor moulds. Formaldehyde by some furniture and materials.

Advice

Identifying the patient we can help… Children with asthma and multiple positive skin tests or specific IgE have more severe asthma than those who are monoallergic.

Take home messages-For all Children Exclusive breast-feeding and avoidance of exposure to environmental tobacco smoke can be safely recommended for the whole population.

Take home messages- For high risk children A Protein hydrolysate as a supplement or alternative for children who cannot breast feed seems to provide further protection. In- utero and post natal smoking and paternal smoking increases respiratory risks. House dust mite allergen avoidance show some protection against atopic dermatitis and asthma in later childhood.

Take home messages- For high risk children  Pets?-further research!! Identifying children with sensitization of utmost importance in targeting advice, educational resources and improving quality of life for asthma sufferers.

Thank you

Future treatments Immunostimulatory DNA to treat ragweed sensitivity. Anti-IgE therapy to decrease peanut sensitivity.