In westernised countries, up to a third of children currently have asthma. Part of this “epidemic” has resulted from a change in diagnostic criteria. In Aberdeen in 1964, asthma was diagnosed in 73 of 261 (28%) participating children with wheeze, in 1989 in 331 of 675 (49%),1 and in 1994 in 654 of 1025 (64%).2 Thus, even if the prevalence of wheeze had remained constant, the prevalence of diagnosed asthma would have increased, supporting the view that the recent increases in childhood asthma are explained by changing diagnostic fashion3 as well as changes in underlying symptoms. Although a weakness of these studies is their lack of objective measurements, such as bronchial hyper-reactivity, they do include items on suggestive symptoms and thus do not rely entirely on varying fashions in medical diagnosis.
Current trends in the prevalence of childhood asthma and asthma-like symptoms vary from clear increases in some countries to stabilisation or even a fall in others.4 We examined the situation in the United Kingdom by doing a further study in Aberdeen, using the same protocol as in 19891 and 1994.2
Participants, methods, and results
In May 1999, we distributed our questionnaire to the parents of all children attending primary school classes 5 to 7 (mainly aged 9 to 12 years with outliers aged 7, 8, and 13 years) in the schools that had participated in the 1964, 1989, and 1994 studies. The responses were entered into an SPSS database along with the earlier studies.
We distributed questionnaires to the parents of 4209 children; 3537 (84%) were returned. Prevalence of asthma or wheeze and the proportion of children with respiratory symptoms reporting a diagnosis of asthma changed little, although we found small but significant increases in the diagnosis of both eczema and hay fever between 1994 and 1999 (table).
Table 1.
Prevalence of respiratory symptoms and diagnoses of asthma, eczema, and hayfever in children in Aberdeen in 1964, 1989, 1994, and 1999. Values are No (%) unless otherwise stated
|
Relative risk (95% Cl)
|
|||||||
|---|---|---|---|---|---|---|---|
| Question | 1964 (n=2510) | 1989 (n=3390) | 1994 (n=4047) | 1999 (n=3537) | 1989 v 1964 | 1994 v 1989 | 1999 v 1994 |
| Ever had asthma? | 104 (4) | 350 (10) | 789 (20) | 858 (24) | 2.5 (2.01 to 3.08) | 1.9 (1.68 to 2.12) | 1.2 (1.14 to 1.35) |
| Male to female ratio | 2.2:1 | 1.9:1 | 1.4:1 | 1.1:1 | 0.9 (0.82 to 1.11) | 0.9 (0.82 to 0.99) | 0.9 (0.83 to 0.99) |
| Wheeze in past 3 years? | 261 (10) | 675 (20) | 1025 (25) | 986 (28) | 1.9 (1.68 to 2.19) | 1.3 (1.17 to 1.39) | 1.1 (1.01 to 1.18) |
| Male to female ratio | 1.7:1 | 1.4:1 | 1.2:1 | 1.1:1 | 0.9 (0.84 to 1.05) | 0.9 (0.86 to 1.02) | 0.9 (0.88 to 1.03) |
| Asthma diagnosis in children with wheeze in past 3 years | 73 (28) | 331 (49) | 654 (64) | 677 (67) | 1.8 (1.42 to 2.16) | 1.3 (1.19 to 1.42) | 1.1 (0.99 to 1.12) |
| Shortness of breath in past year? | 136 (5) | 341 (10) | 753 (19) | 703 (20) | 1.9 (1.53 to 2.25) | 1.9 (1.65 to 2.09) | 1.1 (0.97 to 1.17) |
| Asthma diagnosis in children with shortness of breath | 57 (42) | 262 (77) | 526 (70) | 528 (75) | 1.8 (1.49 to 2.53) | 1.1 (1.02 to 1.18) | 1.1 (1.01 to 1.215) |
| Persistent nocturnal cough in past 3 years? | * | 475 (14) | 1288 (32) | 1067 (31) | * | 2.3 (2.07 to 2.50) | 0.95 (0.98 to 1.01) |
| Asthma diagnosis in children with persistent nocturnal cough | * | 179 (38) | 527 (41) | 530 (49) | * | 1.1 (0.95 to 1.24) | 1.2 (1.09 to 1.31) |
| Ever had eczema? | 132 (5) | 408 (12) | 714 (18) | 755 (21) | 2.3 (1.89 to 2.77) | 1.5 (1.31 to 1.65) | 1.2 (1.10 to 1.33) |
| Male to female ratio | 0.9:1 | 1.5:1 | 1.0:1 | 1.0:1 | 1.3 (1.03 to 1.53) | 0.8 (0.75 to 0.93) | 1.0 (0.88 to 1.08) |
| Ever had hay fever? | 81 (3.2) | 405 (12) | 511 (13) | 543 (15) | 3.7 (2.93 to 4.67) | 1.1 (0.94 to 1.20) | 1.2 (1.09 to 1.44) |
| Male to female ratio | 1.0:1 | 1.6:1 | 1.3:1 | 1.1:1 | 1.2 (0.97 to 1.55) | 0.9 (0.83 to 1.03) | 1.0 (0.86 to 1.07) |
The question in 1964 related to recurrent rather than persistent cough.
The male to female ratio for the diagnosis of asthma has narrowed considerably in the past 35 years, with almost complete disappearance of the previous male preponderance.
Comment
In Aberdeen, the prevalence of symptoms suggestive of asthma now seems to be stable. The proportion of children with symptoms in whom asthma has been diagnosed is high, suggesting that the widespread publicity given to asthma has paid off. Indeed, a higher rate of diagnosis might well be undesirable, leading to asthma drugs being given inappropriately—for instance, to children with chronic cough.5 Nevertheless, the continuing increases between 1994 and 1999 in diagnosed eczema and hay fever suggest that the tendency for children to develop allergies is still increasing, although these increases may also in part reflect changes in diagnostic fashion.
What is already known on this topic
During the past 15 years, the prevalence of childhood asthma and symptoms suggestive of asthma have risen
What this study adds
The rate of rise in the prevalence of childhood asthma has slowed, although a quarter of primary school children have been diagnosed as having asthma at some time in their lives
Most of the recent increase can be attributed to increased diagnosis in children with symptoms; increase in wheeze is barely significant
This article was posted on bmj.com on 24 June 2004: http://bmj.com/cgi/doi/10.1136/bmj.38139.666447.F7
Contributors: AD, SDK, and HW shared responsibility for the planning and day to day running of the 1999 study. TN shared responsibility for the planning of the 1989, 1994, and 1999 studies and for the day to day running of the 1989 study. MO shared responsibility for the design of the 1994 and 1999 studies and for the day to day running of the 1994 study. All authors analysed the data, discussed and interpreted the results, and prepared this report. GR had overall responsibility for funding, design and supervision of the 1989, 1994, and 1999 studies. GR is guarantor.
Funding: Grampian University Hospitals Children's Respiratory Fund, into which GR paid his earnings from drug trials, medico-legal reports, lectures, adoption medical examinations, etc. A generous donation was received in memory of Stuart Kerr.
Competing interests: None declared.
Ethical approval: Grampian Research Ethics Committee.
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