FIRS The Global Impact of Respiratory Disease – Second Edition | Page 15

Asthma
Scope of the disease
Asthma affl icts up to 334 million people
worldwide [4] and its incidence has been
increasing for the past three decades [5]. It
affects all ages, races and ethnicities, though
wide variation exists in different countries and
in different groups within the same country.
It is the most common chronic disease in
children and is more severe in children
living in non-affl uent countries [23]. In these
settings, underdiagnosis and under-treatment
are common, and effective medicines may
not be available or affordable. The burden of
asthma is high [4, 10]. It is one of the most
frequent reasons for preventable hospital
admissions among children in high-income
countries, but less information is available
from low- and middle-income countries [4].
In some studies, asthma accounts for more
than 30% of all paediatric hospitalisations
and nearly 12% of readmissions within 180
days of discharge [24]. It is not widely realised
that asthma causes about 489,000 deaths per
year or more than 1,300 deaths per day [1].
Recent evidence indicates that children with
asthma may have abnormal lung growth and
are at risk for developing lifelong respiratory
compromise and COPD [25].
The causes of the increase in global prevalence
of asthma are not well understood. Genetic
predisposition, exposure to environmental
allergens, indoor and outdoor air pollution,
lower respiratory tract infection early in life,
airway microbiome makeup, dietary factors
and abnormal immunological responses may
promote the development of asthma. The
timing and level of exposure to allergens,
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infection or irritants may be major factors
leading to the development of disease. Early
viral infections and passive tobacco smoke
exposure have been associated with the
development of asthma in young children.
Airborne allergens and irritants associated
with asthma occur in the workplace and
can lead to chronic and debilitating disease
among workers if the exposure persists.
Prevention
The cause of most asthma is unknown and
there is no effective strategy for primary
prevention. However, potentially modifi able
risk factors for development of asthma include
smoking during pregnancy and use of broad-
spectrum antibiotics in the fi rst year of life.
Asthmatics who smoke have a more rapid
decline in lung function than lifelong non-
smokers. Avoiding smoking during pregnancy
and avoidance of passive smoke exposure after
birth can reduce asthma severity in children.
Epidemiological interventions involving work-
related asthma show that, in adulthood, early
removal of allergens or irritants may lead to
better control of the disease, although the
burden and cost of the intervention need
to be taken into account. There is little
evidence for effective single-strategy indoor
allergen avoidance interventions in adults
outside the occupational context, except for
remediation of dampness and mould. The
use of maintenance controller medication can
effectively prevent intercurrent asthma attacks
with a resultant decline in lung function, and
has been clearly shown to reduce mortality
and hospitalisations [4].
Forum of International Respiratory Societies