Asthma & Allergies: Current Trends & Relationship to Housing Prof Anthony Frew Allergy & Respiratory Medicine University of Southampton

E&W consultation rates for asthma (males)

E&W consultation rates for asthma (females)

UK Consultation rates for allergic rhinitis

E&W consultation rates for asthma st or new episodes/week (per 100,000)

Possible causes of an Increase in the Prevalence of Asthma Labelling / Medical fashion

Allergic disease in Aberdeen children Ninan & Russell BMJ 1992;304:

Wheeze (last 12 mo) Asthma (lifetime) Anderson et al BMJ 2004; 328;1052-3

Asthma prevalence & health care use in Britain

Possible causes of an Increase in the Prevalence of Asthma Labelling / Medical fashion Allergy

Making houses HDM-friendly Bedroom & living room carpets Central heating More humidity Soft furnishings Fluffy toys

Prevalence of allergic disease in Australia Peat et al BMJ 1992;305:1326-9

Allergen Avoidance Unanswered Questions What degree of allergen avoidance is needed for clinical improvement? What is best way to achieve this? How much benefit can be achieved? (symptom control, drug reduction etc) Economics? (cost-benefit etc) Should NHS/3rd party payers foot bill?

Prevalence of allergic sensitisation in Germany Nowak D et al ERJ 1996; 9: Hamburg commercial and administrative traffic ++ prevailing W wind mean SO 2 31  g/m 3 mean TSP 53  g/m 3 ( values) Erfurt industrial little traffic low windspeed mean SO  g/m 3 mean TSP 137  g/m 3

Prevalence of allergic sensitisation in Germany Nowak D et al ERJ 1996; 9: Hamburg 4,500 subjects 0.6% of total 3.5% born outside Germany response rate 80% Erfurt 4,990 subjects 5.8% of total 0.7% born outside Germany response rate 74%

Age-dependent differences in allergic sensitisation Heinrich J et al Allergy 1998; 53:89-93 ECRHS phase 2 data Hamburg n= 972 Erfurt n= 726 skin test to birch, grass, cat, moulds or house dust mite trend linked to early life in new “Western” setting Birth cohort

Age-dependent differences in rhinitis prevalence Heinrich J et al Allergy 1998; 53:89-93 ECRHS phase 1 Hamburg n= 3,153 Erfurt n= 3,254 rhinitis prevalence (ex-questionnaire) possible cultural effect - do patients seek more help for rhinitis in West? Birth cohort

Factors associated with living in Hamburg Nowak D et al ERJ 1996; 9: fewer siblings history of asthma in siblings (not parents) history of atopy in parents and siblings passive smoking older houses; single family houses not using open fires or gas cooking fitted carpets, mildew, cat in house slightly less likely to sleep with windows open in winter

Sensitisation is more frequent in West Principal risk factors for atopy –male, sleeping with windows closed Principal risk factors for NSBR –female, siblings with asthma BUT: E-W difference in NSBR cannot be explained by the known risk factors assessed in this survey Prevalence of allergic sensitisation in Germany Nowak D et al ERJ 1996; 9:

Infections & Allergies URTI in infancy protect against allergy –more siblings  more viral infections –reduced risk of atopy but in established asthma –URTI are major cause of exacerbations –esp in children ~80% of attacks

Allergy: the price of affluence? Atopic disease is the price paid by some members of the affluent classes for their relative freedom from disease Annals of Allergy 1976;37:91-100

Allergy skin reaction rates (%) in 10/11 yr olds: urban-rural gradients apply to cat, not birch

Why is there so much asthma? Two separate questions: Why do so many children start wheezing? Why don’t more of them grow out of it?

Outcome of early wheeze Wheezing up to age 18/12 unrelated to risk of developing atopy by age 7 years risks diverge thereafter atopy  risk of persistence

Does asthma go away? wheeze before 3 years does not predict subsequent asthma 2/3 children with asthma at 10 lose it by 18 early onset asthma is more likely to persist boys are more likely than girls to lose their asthma (because of differential lung growth) inflammation may persist without symptoms

Asthma Epidemiology: Summary Causation is complex Only environmental factors can account for speed of change Increase is likely to have different aetiological factors in different countries Epidemiological studies suggest that changes in housing may contribute to level of sensitisation to domestic allergens