Asthma & Allergies: Current Trends &

Relationship to Housing

Prof Anthony Frew

Allergy & Respiratory Medicine

University of Southampton

E-mail: A.J.Frew@soton.ac.uk

E&W consultation rates for asthma (males) 1971-1991

0102030405060708090

100

0-4 5-14 15-24 25-44 45-64 65-74 >75

1971

1981

1991

E&W consultation rates for asthma (females) 1971-1991

0

10

20

30

40

50

60

70

80

0-4 5-14 15-24 25-44 45-64 65-74 >75

1971

1981

1991

UK Consultation rates for allergic rhinitis 1971-1991

0

100

200

300

400

500

600

0-4 5-14 15-24 25-44 45-64 65-74 >75

1971

1981

1991

E&W consultation rates for asthma 1976-2000

0

20

40

60

80

100

120

140

160

76 78 80 82 84 86 88 90 92 94 96 98 0

0-4

5-14

15+

1st or new episodes/week (per 100,000)

Possible causes of an Increasein the Prevalence of Asthma

• Labelling / Medical fashion

Allergic disease in Aberdeen children

Ninan & Russell BMJ 1992;304:873-875

1964 1989 RR

Asthma 4.1% 10.2% 1.75

Eczema 5.3% 12.0% 2.33

Hay Fever 3.2% 11.9% 3.70

0

5

10

15

20

25

30

35

40

SE Scotland Wales Isles

1995

2002

0

5

10

15

20

25

30

SE Scotland Wales Isles

1995

2002

Wheeze(last 12 mo)

Asthma(lifetime)

Anderson et al BMJ 2004; 328;1052-3

Asthma prevalence & health care use in Britain 1970-2000

0-4 5-14 Adults

Prevalence - x1.5 -

GP contact x10 x5 x3

Admissions x20 x10 x2-3

Mortality Low & falling variable

Possible causes of an Increasein 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 diseasein Australia

Peat et al BMJ 1992;305:1326-9

1981 1991Recent wheeze 17.5% 28.8%Diagnosed asthma 9.0% 16.3%Hay Fever 24.9% 46.7%SOB on exertion 19.2% 20.3%Allergy (HDM) 24.9% 24.5%Allergy (GP) 28.8% 28.8%

Allergen AvoidanceUnanswered 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 GermanyNowak D et al ERJ 1996; 9:2541-2552

Hamburg• commercial and

administrative

• traffic ++

• prevailing W wind

• mean SO2 31 g/m3

• mean TSP 53 g/m3

(1985-89 values)

Erfurt• industrial

• little traffic

• low windspeed

• mean SO2 264 g/m3

• mean TSP 137 g/m3

Prevalence of allergic sensitisation in Germany

Nowak D et al ERJ 1996; 9:2541-2552

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 differencesin 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

0

10

20

30

40

50

1946-51 1952-61 1961-71

Hamburg Erfurt

Birth cohort

Age-dependent differencesin 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?

0

5

10

15

20

25

30

1946-51 1952-61 1961-71

Hamburg Erfurt

Birth cohort

Factors associated with living in HamburgNowak D et al ERJ 1996; 9:2541-2552

• 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 GermanyNowak D et al ERJ 1996; 9:2541-2552

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

Sweden Sweden Poland Estonia Estonia

Rural Urban Konin Tallinn Tartu

Any 24 35 13.7 14.3 8.3

Cat 12.5 21 2.5 6.1 4.0

Birch 10 12 2.2 2.6 2.3

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