Abstract

Background

The prevalence of childhood asthma in Scotland is one of the highest in the world. The morbidity secondary to allergic diseases is significant in terms of costs to the nation and effects on the family including the child.

Aims

The aims of this study were to describe the prevalence of asthma, eczema and hay fever in the Highlands of Scotland and in the Shetland Isles and to examine factors in relation to quality of life and social deprivation.

Method

A total population survey of 12 year old children using a parent completed questionnaire.

Results

86.3% (2658/3080) returned questionnaires. Of the 2549 questionnaires analysed, 476 (18.7%) reported asthma ever, 362 (14.2%) wheeze in last 12 months, 508 (19.9%) reported hay fever ever and 555 (21.8%) reported eczema ever.

Of the children reporting asthma or wheeze, 35.4% (229/647) had missed school because of asthma or wheeze, 38.0% (246/647) had missed physical education. 62.5% (354/566) of subjects with wheeze ever reported sleep disturbance. Deprivation measured by DEPCAT scores was associated with maternal smoking and bronchitis in the child but not with allergic diseases.

Conclusion

Compared with previous studies, the prevalence of asthma was unchanged but eczema has increased in Highland adolescents. Allergic disease has a significant impact on school attendance and physical activity. Deprivation was associated with maternal smoking and bronchitis in the child but not with allergic diseases. The impact of allergic diseases in rural areas may be different from urban areas.

Keywords   Asthma, Wheeze, Allergic Diseases, Child, Quality of Life, School Absence, Deprivation

 

Introduction

Scotland not only has the highest prevalence of wheezing within the UK^1,2 but the prevalence of asthma is one of the highest in the world³. Within the UK, asthma may still be underdiagnosed and undertreated¹.  The Highlands of Scotland including Skye are no exception; indeed in a previous study in 1992 some 19% of 12 year olds had wheezed in the last 12 months and 14% had asthma reported by a parent⁴. Whilst mortality in childhood asthma is relatively low⁵, morbidity secondary to allergic diseases may be significant in terms of costs to the nation, family effects and the impact on the individual child at home and at school^5,6.

 

Some degree of disability due to asthma is experienced by an estimated 1.4% of all children in the United States, particularly in recently symptomatic adolescents^7,8. Disability includes time missed from school especially in children with nocturnal wakening, limitation of day to day activities including sport, social effects and emotional strain^5,7,8,9.  The Scottish studies describing quality of life relate to young children with asthma in Aberdeen¹⁰. We speculated that the effects of asthma on quality of life in an adolescent population in a relatively unpolluted and affluent rural area might be different to those described in urban and often very deprived areas.

 

In this study we have estimated the prevalence of asthma, eczema and hay fever in the Highlands of Scotland and in the Shetland Isles. The principal aims of the study were to describe the impact of asthma and wheeze on school and home activities and to explore the relationship between deprivation and the above allergic diseases.

 

Methods

Ethical approval was granted by the Ethics Committees for Highland and Shetland.

All children aged 11-12 years in first year at all secondary schools throughout the Highland mainland, Skye and Shetland, were invited to take part in a parent completed questionnaire survey, distributed by the schools during the spring term 2000. Questions were asked with regard to allergic disease prevalence, treatment and factors commonly associated with deprivation such as bronchitis and maternal smoking. The basic survey instrument was identical to that used in Highland in 1992⁴. Additional questions were included about attendance at hospital, doctor visits, school absence and participation in activities (Appendix A). These were based on the questionnaire used in the study of Croydon children by Anderson¹¹.

 

Deprivation category (DEPCAT) scores, as calculated by McLoone based on post code and Carstair’s index of deprivation¹², were used in the analysis of deprivation effects on prevalence and quality of life factors. DEPCAT score 1 represents the most affluent areas and score 7 the most deprived areas. For analysis purposes DEPCAT scores 1 and 2 are combined as are scores 5,6 and 7.

Data were analysed using Stata 7.0. Missing responses are included in denominators for univariate analyses but excluded from subsequent bivariate analyses. Chi-square test to assess the association between quality of life factors and gender and Chi-square test for trend to assess the prevalence trend across different DEPCAT subgroups were used. Logistic regression analysis was performed to identify factors contributing to school absence.

 

Results

A total of 3080 questionnaires were distributed and 2658 (86.3%) returned questionnaires. 268 (10.1%) subjects were from Shetland and 2389 (89.9%) from Highland. 109 subjects were excluded from the final analysis as 92 had dates of birth outside the age range and a further 17 reported limited physical activity because of wheeze or asthma but did not report any wheeze or asthma.

Of the 2549 subjects whose data were analysed, 1204 (47.2%) were boys and 1215 (47.7%) were girls and no data on sex were available for 130 subjects. 1837  (72.1%) were born in Highland or Shetland and 1956 (76.7%) had lived in Highland or Shetland for at least 11 years.

 

The prevalence of allergic diseases is illustrated in Table I. Asthma ever, wheeze ever and wheeze in the last 12 months were more common in boys than girls.  There was no sex difference for either reported hay fever ever or reported eczema ever.  In 566 children reporting wheeze ever, the most commonly described triggers were upper respiratory tract infection (90.8%) and running (54.4%). Of 362 children reporting wheeze in the last 12 months, 83.7% had less than 10 attacks, and 16.3% had 10 or more attacks of wheeze per year.

 

528/2549 (20.7%) had used an inhaler at some time in their lives. Of subjects who has wheezed in the last 12 months, 60/362 (16.6%) had no diagnosis of asthma and had never received treatment and four of these (4/60), reported 10 or more attacks of wheeze per year.

 

A total of 1758/2549 (69.0%) children missed school for any reason during the last 12 months.

243 (9.5%) missed school because of wheeze or asthma. Table II shows detailed information on 647 children who reported asthma or lifetime wheeze ever. Among these children, 81.5% had missed school in the previous 12 months for any reason and 35.4% missed school because of asthma or wheeze, of whom the majority missed school more than once.  Most school absences were less than 6 days. Over a third had missed physical education at some time, and a smaller proportion reported interference with home activities. The most common home activities limited by wheeze or asthma were sports (18 subjects) and housework (17 subjects).

Few children required hospital admissions, visits to Accident and Emergency (A and E) departments or doctor visits.

Of those children who reported wheeze ever, 62.5% (354/566) reported ever having their sleep disturbed by it at some point in their lives.

 

More girls than boys reported interference with home activities (p = 0.04) or physical education,

(p = 0.023). For all other quality of life factors examined there was no significant difference between boys and girls.

 

 

Table III shows disease prevalence and maternal smoking across deprivation categories. There was no association between allergic disease prevalence and deprivation category. However bronchitis in the child and maternal smoking were significantly associated with deprivation.

The proportion of children who missed school for any reason was not significantly greater in the most affluent areas, 73.9% (230/311), compared to the most deprived areas, 66.3% (69/104). However, a greater proportion of children missed school due to asthma or wheeze in the most affluent areas, 12.9% (40/311), compared with 6.7% (7/104) in the most deprived areas (p = 0.016).

 

Discussion

The methodology for the prevalence study was identical to that used previously in the Highlands of Scotland,⁴ except that on this occasion the total population rather than a sample was studied. As previously, an excellent response rate was achieved. The morbidity questions had previously been used in the Croydon study¹¹ but our methodology differed as we did not undertake a parent interview and our sample was of a total population. This, the third Highland study, provides an ideal opportunity to examine trends in prevalence in a relatively stable population where the percentage of incomers is virtually unchanged since1992⁴.  However it should be recognised that repeated surveys are subject to bias and external influences which are difficult to quantify. Indeed Magnus concludes from a review of 16 cross-sectional studies that the evidence for an increase in the prevalence of asthma and wheezing was weak because the measures used were susceptible to systematic errors¹³. 

There is currently much debate as to whether the prevalence of asthma is continuing to rise, is remaining stable or indeed may even be decreasing^14,15,16.  In Highland, the prevalence of wheeze in the last 12 months has fallen since 1992, whilst in contrast the prevalence of eczema over the same time scale has shown a steady increase (Table IV). The fall in wheeze prevalence is not accounted for by a change in the number of subjects receiving treatment, nor is it likely to be explained by a change in the prevalence of infection related wheeze given the older age group of the subjects studied. Parents’ understanding of the term wheeze has been shown to differ from epidemiological definitions¹⁷. This is unlikely to explain our finding of a decrease in wheeze prevalence as a previous Highland study showed that parents over-report the symptom of current wheeze (19%) and asthma (14%) when compared with objective markers of bronchial hyperreactivity (10%)⁴. Moreover, the question on wheeze used in our studies defines wheeze as “a whistling noise coming from the chest” which we believe makes it less likely that wheeze will have been confused by the rattling noises described by Elphick¹⁸.

Unfortunately, we do not have earlier data with which to compare our results and a rise in wheeze prevalence may or may not have occurred prior to the first study in 1992. It may be that the pattern of prevalence in this relatively sparsely populated and unpolluted rural area is different to elsewhere in the UK.  There is no evidence to suggest a change in the presentation of allergic disease, as in keeping with previous Highland studies⁴ asthma and wheeze were more prevalent in boys than girls and the commonest triggers for wheeze were upper respiratory tract infection and running.

 

Asthma continues to be under reported on questionnaires. Although most untreated subjects reported only infrequent wheeze, it is worrying that a diagnosis was not reported in 4 subjects who had 10 or more wheezing attacks in the past year. In this connection, we emphasise that although we are reporting parental awareness of a diagnosis of asthma, and that the diagnosis may well have been made by the child’s medical practitioner, it is essential for the adequate management of asthma that the family should be aware of the diagnosis.

 

Our study showed that the majority of children with asthma or wheeze (81.5%) reported absence from school for any reason but only 35% missed school in the last year because of wheeze or asthma. This was higher than the 17% reported for Welsh children¹⁹ but considerably lower than Anderson’s study of Croydon children which found that 58% of symptomatic children in the study population missed school in the last year because of wheezing illness¹¹. However the Croydon children were of a younger age group (mean age 8.9 years). Indeed an age effect has been demonstrated in a recent study by Bener et al  who showed a significantly lower absence rate in older children compared to younger pupils²⁰. That study also showed that 43% of asthmatic or wheezy children in the 10-14 year age group missed at least one day compared to 31.5% in our study²⁰. The majority of our children lost between 1 and 5 days from school compared to the median loss of 3 days per year in a Swedish study of children aged 7 – 15 years²¹. A relatively small number of children (1.5%) had missed 16 or more days. Although age may explain the differences between these studies, asthma management may also be important as the Croydon study¹¹ was reported in 1983 before the launch in 1990 of the British Thoracic Society Guidelines on asthma management. It is notable that the majority of children who had missed school had done so on up to 4 occasions during the year, as the literature suggests that frequent brief absences can have a greater detrimental affect on academic performance than an occasional long absence²².

 

Our study results are consistent with others in that more girls than boys missed school because of asthma despite a higher prevalence in boys²⁰. This sex difference maybe a reflection of differing health perceptions, as it has been shown that upper-middle class females report lower health perception scores than upper-middle class and working class boys²³.

 

The parents of 38% of subjects with wheeze or asthma reported interference with physical education, which is higher than the 24% reported in the study of Croydon children¹¹ but considerably lower than the 60% reported in a self completed questionnaire study of Australian adolescents²⁴. This difference may be related to several factors including differing methodology, health perceptions, diagnostic criteria for asthma, the age group studied, or compliance with treatment.

 

In a study of 5 to17 year old American children, more than 40% of asthmatics had woken at least one night during the month prior to the survey⁹.  In our study 62% of subjects who had ever wheezed reported sleep disturbance at some time in their lives This a particularly important finding as Diette showed that night-time wakenings not only affected school attendance and performance but also parents’ attendance at work⁹.

The relatively few hospital admissions and visits to Accident and Emergency Departments reflect that asthma is mainly managed in primary care particularly in rural areas where there are long distances between home and hospital services.

 

When comparing with other studies, it is important to bear in mind methodological differences between studies. We studied children attending secondary schools, whereas many studies have focused on primary school children in whom asthma-related morbidity tends to be higher. Moreover, our questionnaires were parent-completed, in contrast to some studies in which the children have answered the quality of life questions, a feature that is known to influence the results²⁵.

 

The absence of a statistically significant association of wheeze with deprivation was consistent with the findings of Strachans’ UK study²⁶, but is in contrast to the findings of recent literature from North America which demonstrated an association of asthma with deprivation⁸.

The Carstairs score used in our study has been critisied as being a poor index of deprivation in rural areas²⁷. However, there is at present no satisfactory alternative and we have no reason to believe that the use of this deprivation index influenced our conclusions, as the DEPCAT scores for the North of Scotland compare well with data on free school meals, which is often used in paediatric practice as a marker for social deprivation. The percentage of children entitled to take a free school meals in secondary schools in accordance with the Education (Scotland) Act 1980 was 12.1% in Highland and 6.4% in Shetland, compared to 16.7% for Scotland as a whole (figures courtesy of Scottish Executive National Statistics Publication –http:/www.scotland.gov.uk/stats/bulletins/00112-00.pdf), suggesting relative affluence in our study area. The majority of subjects (80%) in our study were from areas classified as DEPCAT score of either 3 or 4 and this may have limited the chances of demonstrating association with deprivation. We did however demonstrate a relationship between bronchitis and deprivation, and also the expected association between maternal smoking and deprivation.  In this respect our data can be compared to a Canadian study, in which no association with asthma and deprivation was reported, but more children with cough or exercise induced bronchospasm were from disadvantaged families²⁸.  They do however contrast with an Aberdeen study in which deprivation was associated with wheeze independent of parental smoking²⁹. 

Never the less, it is possible, but as yet unsubstantiated, that the influence of deprivation may differ between rural and urban settings.

 

The relative affluence of the area studied may explain the relatively low school absence rate because of asthma, as a study of Tayside children showed that school absence was a poor marker of asthma morbidity and was more likely to be influenced by social deprivation³⁰. However, in contrast to Tayside, children in our study from more affluent homes were more likely to miss school although the number of children in the most deprived areas in our study was too small to permit definitive comment.

 

Conclusion

The prevalence of wheeze in Highland has decreased since 1992 whilst that for eczema has shown a steady increase. This supports the view that there may be differing aetiological pathways for asthma and eczema. Whilst childhood asthma may not in general be life threatening the impact on a child’s quality of life can be significant. This study shows that the majority of asthmatics have sleep disturbance and many report absence from school or restriction in physical activity. Comparisons with other studies should be interpreted with caution in view of methodology differences and the lack of recent studies particularly in the UK and Scotland. However, this study raises the possibility that there may be differences in the impact of allergic diseases and asthma in rural, sparsely populated, moderately affluent areas, compared to previously reported urban populations.

 

Acknowledgements

We wish to acknowledge the support of Chest, Heart and Stroke Scotland who once again have funded our endeavours.  We also wish to thank Mrs. Margaret Lamond for the excellent fieldwork that she undertook and finally but not least the schools, parents and pupils who made the study a success.