1.1 Definition
In the 1992 international concensus statement,
asthma was defined as an inflammatory disease of the bronchi, marked by increased numbers
of inflammatory cells such as mast cells and eosinophilic white blood cells. In asthmatic
individuals, inflammation causes symptoms including obstruction of the bronchi of varying
degrees which subsides either spontaneously or in response to therapy. Inflammation
increases the sensitivity of the bronchi to many irritants.
According to the Finnish legislation on occupational disease, occupational asthma refers
to asthma resulting from exposure to biological, chemical or physical irritants. The
causality between asthma and the exposure agent must be established with sufficient
probability.
1.2 Prevalence
Asthma is one of the commonest public health
problems in Finland. After hypertension and coronary heart disease, it is the third
commonest chronic disorder requiring medication. It is also the commonest chronic disorder
in children.
Extensive epidemiological population studies on the incidence and prevalence of asthma in
Finland are few. Roughly 150,000 Finns, or three per cent of the population, have been
diagnosed as asthmatics. A similar percentage of the population is on drug therapy or to
social security because of asthma. Depending on the methodology, study material and
definition of asthma, the prevalence rate may be up to five per cent or 250,000
individuals. The diagnosis of asthma is inaccurate as some individuals only have
occasional asthma-like symptoms, such as prolonged cough and mild respiratory distress,
without observable impairment in pulmonary function tests. These symptoms may be
associated with strain, respiratory infections or exposure to allergens and are usually of
brief duration. Some individuals with these symptoms develop asthma.(Fig.1)
The percentage of asthmatic individuals in the
population has increased especially over the past few decades (Fig. 2).
The number of individuals entitled to special reimbursements for medicines prescribed for
asthma has also increased by roughly 10% per year. At the end of 1993, 135,363 people were
entitled to reimbursements, that is 11,000 more than the previous year. Increased rates
reflect in particular increases in subjective illness and its social consequences. There
are also indications that, just as in other industrialized countries, asthma has also
become more prevalent as a disease in Finland. Physical examinations carried out in the
Finnish defence forces showed the prevalence of asthma in young men to be 0.3% in 1966 and
1.7% in 1991.
Nearly 400 working individuals develop
occupational asthma each year. The number of cases of occupational asthma reported to the
occupational diseases register has increased steadily over the past 15 years. Cases of
asthma caused by animal danders (mainly cow's epithelium) and grain dust reported to the
register have increased since 1982 when farmers were included in the legislation on
occupational diseases (Fig. 3).
Prevalence rates reported from several other western countries are higher than in Finland,
ranging from 2 to 10% of the population. Differences in diagnostic criteria and study
methods do not allow reliable comparison of prevalence rates between different countries.
However, asthma is less common among Finnish emigrants in Canada than among other
Canadians. In Finland, mortality from asthma is exceptionally low - just over 100
individuals a year - compared with Anglo-Saxon countries. In Finland, mortality rates from
asthma have for long remained unchanged despite increased numbers of patients, compared
with an increase in many other countries.
The register of patients entitled to special reimbursements for antiasthmatic agents shows
a two-peaked prevalence curve especially for men (Fig. 4).
The number of new cases of asthma, calculated from the number of patients entitled to
special reimbursements for prescriptions of antiasthmatic drugs, increased between 1986
and 1993 fastest in the population below 15 years of age and, in particular, below 5 years
despite the fact that the diagnosis of asthma is more difficult in small children than in
older children (Fig. 5).
The incidence in the elderly decreased, primarily because the majority of patients in this
age group are already entitled to special reimbursements and new cases are rare at this
age.
The importance of asthma in terms of health care and social welfare expenditure has
increased dramatically and continues to do so. Changes in the population age structure
alone will increase the number of asthma patients by 7,000 by the year 2000. If the trend
observed between 1986 and 1993 continues, the number of individuals suffering from asthma
will be 60% higher in 2000 than it is now. Even this may not be the upper limit if the
prevalence of asthma increases at a higher rate than before.
The population percentage of asthmatics shows regional variation (Fig.
6), due partly to differences in diagnostics, treatment practice and reimbursement
policies.
The prevalence of asthma is highest in many municipalities in Central Finland (Fig. 7). In South-West Finland, asthma diagnoses are relatively few.
The difference between the municipality with the highest prevalence and that with the
lowest is over five-fold. The number of asthma patients is highest in Southern Finland
where the number of inhabitants is also highest. Diagnostic variations are manifested in
the fact that in one and the same region asthma may be relatively rare in adults but
common in children or vice versa.
The annual number of bed-days of asthma patients fell from roughly from 186,000 in 1985 to
113,000 in 1990. The number of hospitalized patients fell far less, from 12,600 to 11,000.
The mean age of hospitalized patients decreased from 49 years to 47 years, and the average
length of hospital treatment from 8.9 to 6.7 days.
1.3 Asthmatic population
Twelve per cent of the asthmatic population are
below 15 years of age, 29% are 15-44-year olds, 32% are 45-64-year olds and 27% are over
65. In childhood, asthma is markedly more common in boys than in girls, but in adults the
reverse is true. The reason for this is not known.
Staging of asthma according to the degree of the disorder is problematic as there are no
commonly agreed criteria. In a report published in the late 1980s, asthma patients were
divided into five groups based on given criteria. Most (60%) of the patients were
considered to suffer from mild asthma and one-fifth from severe or very severe asthma
(Table 1). This distribution involved only adults and is probably different in children.
TABLE 1, Distribution of asthma patients
according to severity of disease (%)
| Severity |
Percentage |
Description |
| Very severe |
2% |
Disabling disease, numerous bed-days.
Life-threatening attacks. |
| Severe |
18% |
Wheezing daily, poor general condition, disease
restricts life, severe nocturnal symptoms. Absence from work for several weeks a year. One
in two patients needs hospital treatment. |
| Moderate |
20% |
Symptoms daily but no significant diurnal
variations. Patient avoids exercise, occasional nocturnal symptoms. |
| Mild |
20% |
Periodic symptoms. Patient reacts to e.g. pollen
or intense cold. Symptoms restrict activity 2-3 times a week. |
| Very mild |
40% |
Occasional cough and wheezing that do not cause
major impairment. Respiratory tract sensitive to intense cold and infections. Allergens
cause symptoms of varying degree depending on exposure. |
In a Finnish study, physical strain was reported
to be the commonest factor causing exacerbation of symptoms in adult asthma patients.
Other common factors were weather, psychological factors, odours, tobacco smoke, dusts,
respiratory infections, allergic factors and acetylsalicylic acid.
Asthmatic children and adolescents manage at school relatively well. Most problems occur
in physical education sessions and technical and textile work, and on the way to school
especially in below-freezing conditions and during the pollen season. Although adolescents
have a fairly good self-esteem many fear what the illness may bring in the future. Parents
of children under school age are sometimes overprotective and restrict the child's
activities unnecessarily.
According to surveys, asthma patients are surprisingly often smokers, particularly
pregnant women and young people.
According to a population study, asthma patients perceive their health status as markedly
poorer than the average population. Psychological symptoms are significantly more common
in young asthma patients than among their peers of the same age group. Adult asthma
patients suffer from dependencies and anxiety more than the normal population. Depression
is the commonest disorder in individuals suffering from chronic asthma. Together with
asthma, the patients often suffer from other chronic disorders: more than one-third suffer
from cardiovascular disease and one patient in six is hypertensive and on antihypertensive
medication. Roughly one-third of asthmatics suffer from disorders of the musculoskeletal
system, usually back problems or arthrosis.
1.4 Costs
The overall annual cost of asthma was estimated at
FIM 2.5 billion at the start of the 1990s. This included direct costs resulting from
medical care and changes in working and living conditions, indirect costs relating to loss
of production, and costs resulting from disabilities. Some of these costs are calculatory,
and it should be borne in mind that asthma also gives employment to people and contributes
to the growth of the national product. The costs of severe asthma account for roughly 60%
of the total costs (Fig. 8).
If the number of asthma patients is estimated at 150,000, annual costs of the disease
average FIM 17,000 per patient. The annual costs of severe asthma average FIM 52,000 per
patient, those of moderate asthma roughly FIM 20,000, and those of mild asthma roughly FIM
4,000.
A 50% decrease in the number of patients developing severe asthma would save roughly FIM
500 million a year. A nearly equal sum may be spent if the prevalence of asthma continues
to rise at the present rate. Most of the costs are incurred by adult patients due to their
large number. According to Swedish calculations, the percentage incurred by child patients
of the total cost is roughly equal to their percentage of all asthma patients. However,
the costs of medical care are higher for children than for adult asthma patients.
Should the above mentioned 60% increase in the number of asthma patients occur, the number
of patients in 2004 would be 280,000 compared with the present 150,000. In addition,
patients suffering from asthma-like symptoms account for roughly 10% of the population.
Although it may not be possible to influence the number of patients significantly, the
severity of the disease can be reduced considerably.
If the number of patients suffering from severe asthma could be reduced from the current
30,000 to half that number by 2004 and the number of patients with moderate asthma
remained at the current level, the costs of asthma would fall from FIM 2.5 billion at
present to FIM 2.2 billion, even if the number of patients with mild asthma were to more
than double. If the percentage of patients with severe asthma decreased from the current
20% to 10% and the other presumptions were as above, the costs in 2004 would be similar to
what they are at present.
More than half the costs of severe asthma result from loss of production due to impaired
capacity for work. Most actual
treatment costs result from hospital treatment, not drug therapy. Patients with severe
asthma should be treated so that their capacity for work and functional capacity is
maximized and the need for hospitalizations minimized.
1.5 Summary
The importance of asthma in terms of public health
and economy is outlined in Table 2.
TABLE 2, Asthma as a public health
problem
- Asthma is one of commonest public health problems
in Finland. Although estimates of the increase of its biological prevalence are still
reserved, the number of patients seeking medical care and social security is rising
sharply.
- Patients with severe or moderate asthma are a
minority but account for a great majority of the costs.
- The most effective way to control the increase in
costs resulting from asthma is to reduce the number of severe asthma cases.
- New demands have been made on the diagnosis of
asthma since the definition of the disease changed. The line between asthma and
asthma-like symptoms is flexible. Therefore the population at which preventive measures
and treatment should be targeted becomes larger. There are no generally accepted criteria
for use in determining the severity of the disease.
- By comparison with other public health problems,
studies on the epidemiology and clinical features of asthma are relatively few.