Asthma Flashcards
ISAAC (PHASE I) -
INTERNATIONAL SURVEY OF PREVALENCE AND SEVERITY OF ASTHMA ECZEMA RHINITIS IN CHILDHOOD
Nb. Phase III is repetition of phase I after at least 5 years to determine trends in these diseases
- exact same method but also with recommended rf questionnaire for both age groups
Method
Results
Limitations:
- study population largely recruited by personal contacts (representative and internal validity)
- 52/155 test centres in Western Europe
- 5/155 from US And had lowest participation rate of 79% - rest had 90 plus
Methods
(Population):
- COMPULSORY written questionnaires on prevalence and severity for self completion 13-14yo - self completed
- recommended video q for 13-14
- recommended written q for 6-7 - parents duh
Results
- English speaking countries have highest asthma prevalence
- Little variation in English speaking couNtrieS
- Other countries in Latin America are also high
- NORTHWEST-SOUTHEAST GRADIENT W/I EUROPE
- Inconsistent: asthma and affluence (GNP)
E.g. Within same ethnic group HK vs Guangzhou - Weak and inconsistent: asthma and other atopic conditions
- prevalence doesn’t correlate with risk factors
Global comparisons of asthma prevalence
The International Study of Asthma and Allergies in Childhood (ISAAC)
- largest collaborative epidemiological study of children in the world
- looks at symptom prevalence of asthma rhinitis eczema in almost 2m children in 105 countries
ISAAC PHASE III
Limitations:**
Over representation of Latin americs in phase IIIB - 67/161 - (phase I was 10% centres in Latin American and phase III was 42%).
Results
Little change in overall prevalence
International difference reduced**
Decrease in English speaking countries
Increase in some regions where it was previously low and increase in diagnosis in most regions
Asthma no longer an English speaking disease
How much asthma is attributable to atopy in general population?
Pearce et al, thorax 1999
Available epidemiological evidence (9 adult reviews, 7 children reviews): usually less than half of asthma cases are due to atopy
Nb. Most non asthmatics are atopic also!!!
How much asthma is attributable to eosinophilia I adults of the general population
Douwes et al,thorax2002”
At most half
Remainder may be due to neutrophilic airway inflammation e.g. Triggered by air pollution
Allergen hypothesis - it sucks
I.e. Early Allergen exposure causes asthma
nB established RF do not explain international patterns of time trends
Little evidence (out of five cohort studies done):
- sporik et al had positive results but not significant
- others in association
Some prelim evidence shows high exposure early in life e.g. Cats may be protective mdr
Also little evidence that allergenic exposure has increased over time. If hypothesis is true, it must have increased as asthma prevalence has increased
The hygiene hypothesis
Define
- Increased asthma prevalence could be due to increased susceptibility to the development of sensitisation and or asthma due to other exposures or absence of exposures in utero or in infancy
- Cleaner environment could correlate with loss of protection from childhood infections
Decrease family size increases atopic and asthma risk
Some evidence that childhood infections reduce risk of asthma and atopy
Problems:
- Infectious is supposed to be protective, but higher infection prevalence in Latin America that has higher prevalence - cf spain and Portugal
- hygiene hypothesis only accounts for half of cases if correct within allergen th1/th2 paradigm
Th0-th1,th2
Th1 - ifn gamma, il2 - cytolytic (bacteria and viruses)
Th2-il4,5-induces B cell igE production (allergy, helminth)
Atopy and asthma in rural Poland: a paradigm for the emergence of childhood respiratory allergies in Europe.
[urbanisation and childhood asthma]
Sozanska et so, allergy 2007
We hypothesized that, in south-west Poland, a ‘rural’ protective effect on atopy and respiratory allergies would be most pronounced among children but that at all ages would be stronger among those with a rural background.
METHODS:
A cross-sectional survey of the inhabitants (age >5 years, n = 1657) of Sobotka, a town of 4000 people in south-west Poland: and seven neighbouring villages. We measured and analysed responses to skin prick tests (atopy) and to a standard questionnaire (asthma and hayfever).
RESULTS:
Atopy was very uncommon (7%) among villagers at all ages but not among townspeople (20%, P < 0.001); the differences were most marked among those aged under 40 years. Asthma and hayfever were similarly distributed, both being very rare among villagers. The differences appear to be explained by the cohort effect of a communal move away from rural life. This interpretation is supported by an ecological correlation (rho = -0.59) between rural populations and childhood wheeze in 22 European countries.
CONCLUSION:
The very striking differences in the prevalence of allergy between these two neighbouring communities of central Europe reflect the pan-continental population movements that may have been responsible for the emergence of childhood allergies in Europe.
Similar findings by Weinberg 2000 - review of rural vs urban across 4 studies in 4 countries In Africa
Also asthma decreases with age-0!!!
Global burden of asthma
Now
15% children 13-14 had asthma symptoms in last year
Low as 3% in LMIC
High as 30% in HIC
In 20 years, Upto 30% globally 3-30 LMIC major costs for health serviced and patients in LMIC major burden of chronic disease
Need to improve access to inexpensive treatment and improve asthma management
Established risk factors - no evidence for them
Air pollution hypothesis out the window cos of china and Eastern European low asthma
Fam history?
Alford et al 2004 Fam history is consistently associated
Asthma - neglected epidemic
Pearce et al 2000
Neglected cause global aims are to reduce adult mortality not childhood morbidity
More research needed cos of failed hygiene and allergen hypothesis
