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Is there a new epidemic of hay fever and asthma? What is happening and why? An overview Prof Jean Emberlin The National Pollen and Aerobiology Research Unit |
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The talk set the scene for the theme of the symposium by presenting the latest evidence on the questions of “What have been the trends in the prevalence of hay fever and asthma over recent decades? What are the current patterns and trends? What is the current opinion on the explanation for these patterns?”. Well documented increases in hay fever and asthma prevalences
occurred in the UK through the 1970s and 1980s. For example, in the
case of hay fever, rates in
children increased from about 3% in 1964 to 12% in 1989 in Aberdeen, and from 9% in 1973 to 15% in 1988 in South Wales ( Burr
1989). Upton et al. ( 2000) reported an increase in asthma in west Scotland
from 3% in the late 1970s to 8.2% in 1996 . More recently results from ISAAC report
a hay fever prevalence rate of 35% in 13 to 14 year olds, (Strachan
1997). This is one of the highest rates in Europe. Similarly the corresponding
rate for asthma reported from ISAAC is 33%, one of the highest world
wide. Global maps of the prevalence
of clinical asthma produced
from a combination of results from ISAAC and the ECRHS ( Masoli et al.
2004) show a close correspondence
with affluence. The highest rates occur in
English speaking countries of the western world. In contrast
an almost inverse pattern features in asthma
fatality rates. During the past ten years
asthma rates have stabilised or even declined in several countries including the UK. For example, in school children in Melbourne,
prevalence of asthma decreased from 1993 to 2000. In contrast
reported eczema and rhinitis increased ( Robertson et al. 2004). In
the UK Sutherland and Fleming ( 2004) report a downward trend in asthma
incidence in children since 1993 until
1999 when rates stabilised. The possible reasons for the high rates of asthma and hayfever
were discussed in relation to the latest evidence. For instance over
20 papers have been published in recent years on the protective effects
of livestock farm environments but the role of
endotoxin is still unclear ( Eder and Von Mutius 2004). Conflicting
evidence has been published about
the influence of fevers in the first year of life
and also about the effects of
pet ownership but many papers indicate a protective effect ( Williams
et al. 2004, Gern et al. 2004). The European Pollen
information network has pollen count data for many countries over the
last few decades. Analysis of these records show that
pollen seasons for many
types of allergenic plant are starting earlier and lasting longer due to
recent weather changes which may be linked to global warming. The prolongation
of the pollination period has led to
an increase in the time when hay fever
sufferers may have symptoms. Pollen allergens can interact with pollution particles such
that their antigenic potency is increased. In addition synergistic effects
of pollen and air pollution can
lead to an increase in symptom
severity. For more information on pollen
, aerobiology and pollen forecasts
visit www.pollenuk.co.uk. Burr
et al. (1989) Trends in hay fever Arc
Dis Child 64 pp 1452-6
Eder
W, Von Mutius E (2004) Hygiene hypothesis and endotoxin: what is the
evidence? Curr Opin Allergy Clin Immun 2004 April 4( 2 ). Gern
et al. (2004) Effects of Dog ownership and genotype on immune development
and atopy in infancy J Allergy
and Clinical Immunology 2004 :113 (2) Masoli
et al. ( 2004). The global burden of
asthma: executive summary of the GINA Dissemination Committee
report. Allergy 59: 5. May 469-479 Robertson
et al. (2004) “Asthma prevalence in Melbourne
schoolchildren: have we reached the peak?” Med J Aust. March 2004 :180 (
6) 263-4
Strachan
et al.(1997) International Study of Asthma and allergies in Children.
Pediatric Allergy and Immunology 8
:161-176 Sunderland
RS and Fleming DM (2004)“Continuing decline in acute asthma episodes
in the community” Arch
Dis. Child 2004 March 89 ( 3)
: 282-5 Williams et al ( 2004) Are fevers in the first year of life protective against later
allergic sensitisation? J of Allergy and Clin. Immunol. Feb 2004 vol
113 No 2
Upton
et al. (2000) Intergenerational 20 year trends in the prevalence of
asthma and hay fever in adults: the midspan family study surveys of
parents and offspring. BMJ 2000;BMJ 321:88-92 ( 8th
July)
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