Volume 168 Issue 9

Asthma and other atopic diseases in Australian children Australian arm of the International Study of Asthma and Allergy in Childhood Colin F Robertson, Marita F Dalton, Jennifer K Peat, Michelle M Haby, Adrian Bauman, J Declan Kennedy and Louis I Landau MJA 1998; 168: 434-438 Abstract - Introduction - Methods - Results - Discussion - Acknowledgements - References - Authors' details - - ©MJA1998 Abstract Objective: To determine the prevalence of asthma, eczema and allergic rhinitis in Australian schoolchildren using the protocol of the International Study of Asthma and Allergy in Childhood (ISAAC). Design: Questionnaire-based survey. Setting: Melbourne, Sydney, Adelaide (in winter-spring, 1993) and Perth (in winter-spring, 1994). Subjects: All children in school years 1 and 2 (ages 6-7 years) or in year 8 (ages 13-14 years), attending a random sample of 272 schools, stratified by age and city. Main outcome measures: Parent-reported (for 6-7 year olds) or self-reported (for 13-14 year olds) symptoms of atopic disease in the previous 12 months, or ever; treatment of asthma; and country of birth. Results: 10 914 questionnaires were completed for 6-7 year olds and 12 280 for 13-14 year olds (84% and 94% response rates, respectively). Prevalence of wheeze in the past 12 months was 24.6% for the 6-7 year olds and 29.4% for the 13-14 year olds, and, among 6-7 year olds, was significantly higher in boys (27.4%) than girls (21.7%). Children born in Australia were more likely to report current wheeze than those born elsewhere (6-7 year olds: odds ratio [OR], 1.82; 95% confidence interval [CI], 1.55-2.15; and 13-14 year olds: OR, 1.88; 95% CI, 1.68-2.11). Prevalences of current eczema and allergic rhinitis were 10.9% and 12.0%, respectively, for the 6-7 year olds, and 9.7% and 19.6%, respectively, for the 13-14 year olds. Asthma, eczema and rhinitis coexisted in 1.8% of 6-7 year olds and 2.8% of 13-14 year olds. Conclusion: This study provides evidence that asthma prevalence in Australian schoolchildren is continuing to increase and is higher among Australian-born children than among those born elsewhere. Asthma, eczema and allergic rhinitis coexist to a lesser extent than expected. These results form the basis for future Australian and international comparisons. Introduction There is now substantial evidence that the prevalence of asthma and other atopic disorders is increasing worldwide.1,2 While the prevalence of asthma has been documented in the past 30 years, variation in methods and lack of uniform diagnostic criteria make direct comparison between studies difficult. Little is known about the prevalence of the other atopic disorders -- eczema and allergic rhinitis -- both throughout the world and particularly in Australia. The International Study of Asthma and Allergy in Childhood (ISAAC) is a collaborative project which has developed a standardised methodology to describe the prevalence and severity of asthma, rhinitis and eczema in children throughout the world.3 Such data will provide a framework for aetiological research into lifestyle, environmental and genetic factors affecting these disorders. Phase 1 of ISAAC is to determine the prevalence of the disorders throughout the world. Phases 2 and 3 will be more comprehensive, using more detailed questionnaires and objective measures to confirm the differences seen in Phase 1 and to identify important aetiological factors. Our study was part of Phase 1 of ISAAC. It aimed to determine the prevalence of asthma and other atopic diseases in Australian schoolchildren, to determine the burden of atopic disease in this country, and to provide a basis for international comparison. Methods We used the protocol of ISAAC3 to survey two age groups: 6-7 year olds (school years 1 and 2) and 13-14 year olds (school year 8). Subjects were all children in the relevant years of a random sample of primary and secondary schools. The sample comprised about 10% of all government, Catholic and independent schools in the metropolitan areas of Adelaide and Perth; the area within a radius of 20 km from the GPO in Melbourne; the area within a radius of 10 km from the GPO in Sydney for primary schools (school years 1 and 2); and the Western Region of Sydney for secondary schools (school year 8). Previous studies have shown these areas of Sydney and Melbourne to be representative of the metropolitan areas of these cities.4,5 A five-page questionnaire was issued by teachers for completion by parents of the 6-7 year olds, and by the 13-14 year olds in the classroom under examination conditions. The questionnaires contained the three standard ISAAC modules, asking about symptoms of asthma, eczema and allergic rhinitis3 (see Box 1 for definitions), an additional module about treatment of asthma, and two extra questions about the children's and mothers' country of birth. No translations were provided. If the first questionnaire was not returned by the 6-7 year olds, a second was issued. A second visit was made to the secondary schools, if necessary, to recruit students absent at the initial visit. Data were analysed with the statistical package SPSS-X.9 Results were adjusted for cluster effect, and chi-squared tests were used to compare prevalences, while significance of odds ratios (OR) was assessed with 95% confidence intervals (CIs). Results Details of schools and subjects surveyed are shown in Box 2; 201 primary schools and 71 secondary schools participated, comprising 7%-42% of schools in the sampling area; 9% of schools selected declined to participate. A total of 12 952 questionnaires were issued to the 6-7 years age group (response rate, 84%) and 13 078 to the 13-14 years age group (response rate, 94%). Prevalence of atopic diseases in the two age groups is shown in Box 3. Asthma Prevalence of current wheeze was 24.6% for the 6-7 year olds (95% CI, 23.8-25.4), and 29.4% for the 13-14 year olds (95% CI, 29.1-29.7) (Box 3). In the younger group, current wheeze was significantly more common in boys than in girls (OR, 1.36; 95% CI, 1.25-1.49), but this sex difference was reversed in the older group (OR 0.82; 95% CI, 0.76-0.89). Figure 1 (below) compares the prevalence of atopic diseases between the four cities. For the 6-7 year olds, there was no significant difference in prevalence of current wheeze between cities, but for the 13-14 year olds prevalence was slightly higher in the western cities (Adelaide and Perth: 32.3%) than in the eastern cities (Sydney and Melbourne: 25.9%) (OR, 1.37; 95% CI, 1.26-1.48). There was a similar difference between west and east in percentage of 13-14 year olds who had had more than 12 episodes of wheeze per year (4.1% versus 3.1%) and who had attended the emergency department (3.5% versus 2.9%) (data not shown). The prevalence of current wheeze was generally higher in the older age group. The spectrum of asthma among children who reported current wheeze is shown in Box 4. While most children in both age groups reported only one to three asthma episodes in the previous 12 months, 8.0% of 6-7 year olds and 12.2% of 13-14 year olds reported more than 12 episodes. Sleep disturbance due to asthma was common, with 11.2% of 6-7 year olds and 9.8% of 13-14 year olds reporting sleep disturbance on one or more nights per week. About 7% of both age groups reported a hospital admission for asthma in the previous 12 months. Patterns of asthma treatment are shown in Box 5. Regular b2-agonists were taken as sole therapy by 5.5% of 6-7 year olds and 7.4% of 13-14 year olds with current wheeze, while regular inhaled steroids were taken by 21.1% of 6-7 year olds and 14.6% of 13-14 year olds, rising to 49.7% and 36.9% for those with more than 12 episodes per year. While overall 26.5% of 6-7 year olds with current wheeze and 15.8% of 13-14 year olds had a written asthma management plan, this increased to 46.5% and 25.9% in those who reported 12 or more attacks in the past 12 months. Most children attended a doctor at least once during a wheezy episode throughout the year, but only 42.2% of 6-7 year olds and 31.3% of 13-14 year olds visited a doctor for a regular check-up. Eczema Prevalence of current eczema did not vary significantly between the cities (Box 3). Eczema was less common in boys than in girls in both age groups (6-7 year olds: OR, 0.81; 95% CI, 0.72-0.92; 13-14 year olds: OR, 0.57; 95% CI, 0.51-0.65). Sleep disturbance due to itching was common among those with current eczema; it was reported to occur at least weekly by 7.9% of 6-7 year olds and 13.4% of 13-14 year olds, and at a lesser frequency by 27% of 6-7 year olds and 30.4% of 13-14 year olds. Allergic rhinitis The prevalence of current allergic rhinitis was significantly higher in Adelaide and Perth than in Sydney and Melbourne (6-7 year olds: OR, 1.62; 95% CI, 1.44-1.82; 13-14 year olds: OR, 1.53; 95% CI, 1.40-1.68). Like wheeze, rhinitis was more common in boys than girls in the younger group (boys versus girls: OR, 1.19; 95% CI, 1.06-1.33), while this sex difference was reversed in the older group (boys versus girls: OR, 0.64; 95% CI, 1.40-1.68). Among those with current rhinitis, 71% of 6-7 year olds and 76% of 13-14 year olds reported that it interfered with their daily activity to some extent (troublesome rhinitis), while 18.5% of 6-7 year olds and 19.1% of 13-14 year olds described this interference as moderate to "a lot". Atopic disease and country of birth Children born in Australia were more likely to report current wheeze than those born elsewhere (6-7 year olds: OR, 1.81; 95% CI, 1.54-2.14; 13-14 year olds: OR 1.89; 95% CI, 1.69-2.12). This trend was similar for children whose mothers were born in Australia compared with those whose mothers were born elsewhere (6-7 year olds: OR, 1.29; 95% CI, 1.18-1.42; 13-14 year olds: OR, 1.58; 95% CI, 1.45-1.71). When children born outside Australia were analysed by region of birth (United Kingdom, Central Europe, South-East Asia or the Middle East), there was no difference in the prevalence of wheeze between regions. Eczema and rhinitis were also more common in children born in Australia than those born elsewhere. For eczema the OR was 1.31 (95% CI, 1.06-1.63) for 6-7 year olds and 1.36 (95% CI, 1.14-1.61) for 13-14 year olds. For rhinitis, the OR was 1.79 (95% CI, 1.42-2.26) for 6-7 year olds and 1.5 (95% CI, 1.32-1.70) for 13-14 year olds. The proportion of children born outside Australia was higher in the eastern cities among 13-14 year olds (23%) than in the western cities (15%). Similarly, the proportion of mothers born outside Australia was higher in the eastern cities (54%) than in the western cities (39%). When the odds ratio comparing prevalence of wheeze among 13-14 year olds in western versus eastern cities was adjusted for child's country of birth, it fell from 1.37 to 1.25 (95% CI, 1.15-1.36). Interrelations of atopic diseases Figure 2 (below) shows the overlap of asthma, eczema and allergic rhinitis. While 35.2% of 6-7 year olds reported having at least one of these conditions in the past 12 months, only 1.8% reported having all three. Corresponding figures for 13-14 year olds were 41% with at least one condition and 2.8% with all three. Among those with current wheeze, only 19% of 6-7 year olds and 18% of 13-14 year olds reported coexistent current eczema, with no apparent age effect in the relationship. Discussion This study describes the burden of atopic disease in Australian schoolchildren. The prevalence of current wheeze was similar to that reported in recent epidemiological studies in Australia.10 However, comparison with results of a similar questionnaire given to Melbourne schoolchildren in 1990 suggests that, although the spectrum of asthma remains unchanged, the prevalence of recent wheeze has increased from 23.1% in 1990 (95% CI, 21.7-24.5)4 to 27.2% in 1993 (95% CI, 25.6-28.8) (P < 0.01). The rate of increase (1.4% per annum) is similar to that reported in an earlier Australian study (1.24%)10 and higher than that reported in European studies (0.1%-0.4%).1 Morbidity due to asthma remains significant, with high levels of symptoms, emergency department attendances and hospital admissions. Asthma is the second most common reason for admission to a paediatric hospital bed in Victoria (after otolaryngological conditions), with a rate in children of 738 per 100 000 population in 1994-1995.11 The total annual cost to the community associated with asthma management in Australia was estimated in 1989 as $627 million, or $769 per asthmatic person.12 These costs are likely to have increased because of the increases in medication costs and asthma prevalence. There was a significant difference in the prevalence of current wheeze and current rhinitis between the eastern and western States. A possible explanation is the difference in patterns of immigration, with more children in the eastern cities born outside Australia than in the western cities. Indeed, the odds ratio comparing prevalence of wheeze among 13-14 year olds in western versus eastern cities fell from 1.37 to 1.25 after adjustment for country of birth. Internationally, ISAAC has collected data on over half a million children from 120 centres in 48 countries. Australia ranks third-highest in prevalence of current wheeze for 13-14 year olds and second-highest for 6-7 year olds.13 For "current rhinitis", Australia ranks fifth and, for eczema, eleventh. Australia's high ranking for asthma prevalence is supported by data for asthma mortality. This was not collected by ISAAC, but comparison of available data from 11 developed countries shows Australia had the highest mortality rate due to asthma in 1990.14 We found evidence from throughout Australia for continuing lack of effective treatment of asthma. Among children with more than 12 episodes of wheeze per year, only 64% of 6-7 year olds and 43% of 13-14 year olds were taking regular preventive treatment. Further, 5.5% and 7.4% of those reporting "current wheeze" used regular b -agonists in the absence of any preventive therapy, despite the cumulative evidence against the practice. Sodium cromoglycate was used by 19% of the 6-7 year olds and 11% of the 13-14 year olds who reported taking regular preventive therapy, showing some support for the Australian paediatric asthma guidelines, which recommend cromoglycate as first-line therapy for mild to moderate persistent asthma.15 We also found eczema and rhinitis to be common and to cause significant morbidity among Australian schoolchildren. Eczema was less common in boys than in girls in both age groups, a trend seen throughout the world.16 It is not life-threatening, but may cause considerable physical and psychological disability (including discomfort from itching, which may result in sleep loss and secondary infection, as well as the psychological effects of a visible skin disease). Treatment can be expensive and time consuming. Recent Australian estimates of the cost to the family were $330 to $1255 a year, depending on eczema severity.17 Additional costs to the community for consultations ranged from $209 to $642 a year for each child. Allergic rhinitis also carries significant morbidity. The effect on quality of life of perennial rhinitis has been estimated to be similar to, or worse than, mild to moderate asthma.18 In adults, hayfever is estimated to cause, on average, the loss of a third of a day from work each year, in addition to loss of productivity through symptoms or the sedating effects of some drug treatments.18 There are no precise estimates for the cost of therapy, as many sufferers do not consult a medical practitioner,8 and most treatment is available "over the counter". The higher prevalence of "current wheeze" found among 13-14 year olds compared with 6-7 year olds should be interpreted with caution, as the respondents differed between the two groups (parents for the 6-7 year olds and the children themselves for the 13-14 year olds). In an earlier study of Melbourne 7-year-olds and 15-year-olds, in which parents completed the questionnaire for both age groups, prevalence of "current wheeze" was lower among the 15-year-olds (18.6%) than among the 7-year-olds (23.1%).4 Further, comparison of adolescent and parent responses to an Australian asthma morbidity questionnaire showed that the adolescents reported a higher incidence of symptoms than their parents.19 The correlation between the three atopic diseases was less than anticipated. Atopy is usually associated with increased serum levels of IgE and positive skin reactivity to common allergens and has a strong genetic basis. The factors that determine the phenotypic expression of atopy and direct it to asthma, eczema or hayfever are unclear. This diverse expression of the genotype needs to be considered when studying the genetics of asthma. In conclusion, Australia has a high prevalence of atopic disorders, ranking among the highest in the world. Our study, part of a much larger international study, provides an opportunity to gain new insights into the causes and natural history of these disorders. Acknowledgements We would like to thank the schools, parents and children who participated, the research assistants who helped collect the data, and the State departments of education that approved the study. In Adelaide, the study was supported by Rotary, in Perth by the Asthma Foundation of Western Australia, and in Melbourne and Sydney by internal department funds. References Magnus P, Jaakkola JJK. Secular trends in the occurrence of asthma among children and young adults: critical appraisal of repeated cross sectional surveys. BMJ 1997; 314: 1795-1799. Wuthrich B. Epidemiology and natural history of atopic dermatitis. Allergy Clin Immunol Int 1996; 83: 77-82. Asher I, Kiel U, Anderson HR, et al. International study of asthma and allergies in childhood (ISAAC): rationale and methods. Eur Resp J 1995; 8: 483-491. Robertson CF, Heycock E, Bishop J, et al. Changes in prevalence of asthma in Melbourne schoolchildren over 26 years. BMJ 1991; 302: 1116-1118. Peat JK, Toelle BG, Gray EJ, et al. Prevalence and severity of childhood asthma and allergic sensitisation is seven regions of New South Wales. Med J Aust 1995; 163: 22-26. Jenkins MA, Clarke JR, Carlin JB, et al. Validation of questionnaire and bronchial hyperresponsiveness against respiratory physician assessment in the diagnosis of asthma. Int J Epidemiol 1996; 25: 609-616. Williams HC, Burney PGJ, Pembroke AC, Hay RJ. Validation of the UK diagnostic criteria for atopic dermatitis in a population setting. Br J Dermatol 1996; 135: 12-17. Sibbald B, Strachan DP. Epidemiology of rhinitis. In: Busse WW, Holgate ST, editors. Mechanisms in asthma and rhinitis: implications for diagnosis and treatment. Oxford: Blackwell Scientific Publications, 1994: 32-43. Norusis MJ. SPSS/PC+ Advanced Statistics. V5.0 [computer program]. Chicago, Ill:SPSS Inc, 1992. Peat JK, van den Berg RH, Green WF, et al. Changing prevalence of asthma in Australian children. BMJ 1994; 308: 1591-1596. Information Analysis Unit, Acute Health, Victorian Department of Human Services. Victorian inpatient mordibity database. Melbourne: Department of Human Services. Sighted Oct 1997. Toelle BG, Peat JK, Mellis CM, Woolcock AJ. The cost of childhood asthma to Australian families. Pediatr Pulmonol 1995; 19: 330-335. Beasley R, Keil U, von Mutius E, et al. Worldwide variation in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis and atopic eczema: the international study of asthma and allergies in childhood (ISAAC). Lancet 1998. In press. Robertson CF, Sennhauser F, Mallol J. The change in prevalence and severity of asthma in developed and developing countries. Phelan PD (ed). Baillieres Clin Paediatr 1995; 3: 253-275. National Asthma Campaign. Asthma management handbook. 3rd edition. Melbourne: National Asthma Campaign, 1996. Williams HC, Robertson CF, Stewart AW, et al. Worldwide variation in the prevalence of symptoms of atopic eczema in the International Study of Asthma and Allergies in Childhood. J Allergy Clin Immunol 1998. In press. Su JC, Kemp AS, Varigos GA, Nolan TM. Atopic eczema: its impact on the family and financial cost. Arch Dis Child 1997; 76: 159-162. Juniper EF. Measuring health-related quality of life in rhinitis. J Allergy Clin Immunol 1997; 99: S742-S749. Bishop J, Robertson CF, Caust J, et al. Concordance between adolescent and parent response to an asthma morbidity questionnaire. Am Rev Respir Dis 1993; 147: A373. Received 30 Oct 1997, accepted 10 Mar 1998 Authors' details Department of Thoracic Medicine, Royal Children's Hospital, Melbourne. Colin F Robertson, MSc, FRACP, Deputy Director; Marita F Dalton, Assoc Dip Med Rec, Research Assistant. Department of Medicine, University of Sydney, Sydney. Jennifer K Peat, PhD, Senior Research Fellow; Michelle M Haby, MAppSc, Research Assistant. School of Community Medicine, University of New South Wales, Sydney. Adrian Bauman, PhD, FAFPHM, Associate Professor. Department of Respiratory Medicine, Women's and Children's Hospital, Adelaide. J Declan Kennedy, MD, FRCP, Physician. Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth. Louis I Landau, MD, FRACP, Professor of Paediatrics. Reprints will not be available from the authors. Correspondence: Dr C F Robertson, Department of Thoracic Medicine, Royal Children's Hospital, Flemington Road, Parkville, VIC 3054. E-mail: cfrobATcryptic.rch.unimelb.edu.au Readers may print a single copy for personal use. No further reproduction or distribution of the articles should proceed without the permission of the publisher. For permission, contact the Australasian Medical Publishing Company Journalists are welcome to write news stories based on what they read here, but should acknowledge their source as "an article published on the Internet by The Medical Journal of Australia <http://www.mja.com.au>". <URL: http://www.mja.com.au/> © 1998 Medical Journal of Australia.

Colin F Robertson · Marita F Dalton · Jennifer K Peat · Michelle M Haby · Adrian Bauman · Louis I Landau

Problem-based learning: its rationale and efficacy Paul M Finucane, Steve M Johnson and David J Prideaux For editorial comment see Schmidt Problem-based learning (PBL) in medical education uses clinical cases as the context for students to study basic and clinical sciences. Its possible advantages over traditional approaches include its greater relevance to the practice of medicine, its ability to promote retention and application of knowledge, and its encouragement of self-directed life-long learning. Possible disadvantages include higher costs, both in resources and staff time. Although its efficacy is difficult to evaluate, the current enthusiasm for PBL seems justified and its use is likely to increase further. (MJA 1998; 168: 445-448) Introduction - What is PBL? - Rationale for using PBL - Is PBL effective? - Advantages of PBL - Disadvantages of PBL - Future directions in PBL - Acknowledgements - References - Authors' details - - ©MJA1998 Introduction Medical schools [which fail to implement educational reform] will continue to graduate doctors who are, on the whole, largely adequate, but who could be so much more. Max Kamien1 After much criticism and calls for reform in medical education,2-4 several Australian medical schools have made fundamental changes in student selection processes, curricula, teaching strategies and assessment methods. The Karmel Report in 19735 -- which concluded that Australian medical school curricula were too science- oriented, not innovative and neglected primary care -- stimulated changes in existing medical schools. It also led to the establishment of a new medical school in Newcastle, in 1978, with a mandate for innovative approaches to medical education.6 Among its many innovations, the Faculty of Medicine at Newcastle emphasised learning through the study of clinical problems (ie, problem-based learning [PBL]).7,8 Although new to Australia, PBL was by then well established at overseas institutions, most notably McMaster University in Canada, where PBL was introduced in the medical curriculum in 1969.9,10 The PBL "experiment" has been endorsed as an educational strategy by the World Federation of Medical Education11 and the World Health Organization.12 By 1991, some 100 medical schools in the United States had embraced PBL to varying extents,13 and PBL is now an entrenched component of medical school programs in Canada, the United Kingdom, the Middle East and Asia.14 PBL is widely accepted in Australia, and the three medical schools with recently developed graduate entry programs (Flinders University of South Australia, the University of Sydney and the University of Queensland) have based their new curricula on PBL.15 Other Australian medical schools are also adopting PBL. By the year 2000, more than 50% of Australia's doctors will have graduated from schools with PBL-based curricula. While PBL has been developed primarily for the early years of medical education programs, there is increasing interest in PBL in the clinical years.16-18 What is PBL? Definitions of PBL vary, but a comprehensive example would be "an educational method characterised by the use of patient problems as a context for students to learn problem-solving skills and acquire knowledge about the basic and clinical sciences".19 Students usually meet in small groups two or three times a week for PBL tutorials. They are presented with a clinical problem (eg, a patient with chest pain), and, in a series of steps, they discuss possible mechanisms and causes, develop hypotheses and strategies to test the hypotheses, are presented with further information, and use this new information to refine their hypotheses, finally reaching a conclusion. A tutor usually acts as a facilitator, guiding students in this group-learning process. In the course of this exercise, students identify both their existing levels and gaps in their knowledge. These gaps form the basis for independent learning outside the PBL tutorials. The identification and pursuit of these so-called "learning goals" is a key element of the PBL process. Rationale for using PBL The PBL approach is based on principles of adult education20 and cognitive psychology.21 It differs fundamentally from traditional curricula, in which students acquire "background" knowledge of the basic sciences in the early years of the course and in the later years apply this knowledge to the diagnosis and management of clinical problems. This traditional approach has been criticised for a number of reasons:4,22,23 It creates an artificial divide between the basic and clinical sciences; Time is wasted in acquiring knowledge that is subsequently forgotten or found to be irrelevant; Application of the acquired knowledge can be difficult; The acquisition and retention of information that has no apparent relevance can be boring and even demoralising for students. Theoretically, PBL, with its educational objectives24 (Box 1), can avoid many of these problems.25 Various disciplines, particularly the basic and clinical sciences, are integrated throughout the curriculum. As students attempt to understand and solve clinical problems, they learn about normal bodily structure and function, and apply this knowledge to their search for a solution. Learning occurs in context and builds on what students already know. In theory, this process can aid retention,10,21,26,27 add interest14,19,21 and increase motivation to learn.21 Students (with initial help from tutors) determine both their own learning needs and the strategies they need for learning (eg, the efficient accessing of library resources or the formation of study groups). Is PBL effective? The efficacy of PBL is difficult to evaluate,28 as it is generally introduced together with other changes in the curriculum and along with changes in student selection, staff development, and assessment procedures. With so many confounding variables, it is hard to determine the extent to which PBL contributes to any detected change in outcomes. Many of the early claims for its effectiveness were based on the anecdotal evidence of enthusiasts. Empirical research often consisted of small and highly specific studies from single centres, and the ability to generalise from such findings is uncertain. Pooling information to gain an overview of the advantages of PBL is difficult and may be misleading. For example, there are considerable differences in what individual medical schools even consider to be PBL.29 Conclusions about the effectiveness of PBL are thus tentative, and the methodological and logistical problems which constrain educational research make it very difficult to conduct randomised controlled trials. Indeed, few such trials have been, or are ever likely to be, undertaken. Advantages of PBL The justification for PBL lies in its compatibility with modern theories of adult learning, together with evidence of efficacy in some areas. Recent reviews highlight the aspects of PBL generally agreed to be effective and those aspects whose efficacy is controversial19,21,28,30 (Box 2). Most students enjoy the active participation which PBL fosters and consider the process to be relevant, stimulating and even fun,19,31 while teachers tend to enjoy the increased student contact.19 Students and teachers report that the learning environment created by PBL is more convivial as traditional barriers between students and faculty are lowered.14 There is convincing evidence that PBL fosters self-directed learning skills10,21,26,27,32 and this may help medical school graduates to be life-long learners.32-34 PBL activities also bring together faculty from different disciplines, initially in planning and developing the curriculum and later in teaching and assessing students -- promoting interaction between basic scientists and clinicians. This can have important spin-offs in fostering collaborative research, improving the delivery of clinical services and enhancing the work environment. In other areas, however, PBL seems not to have lived up to expectations. There is no evidence that PBL curricula are any better than traditional curricula in achieving one of their prime aims -- the fostering of clinical reasoning and problem-solving skills. Also, while there is both theoretical support and anecdotal evidence that PBL enhances motivation and helps in the development of interpersonal skills, these effects have never been proven.30 Disadvantages of PBL The criticism most often voiced is that PBL is costly, in demands of staff time and teaching materials and other physical resources (Box 3). Both initial and on-going costs should be considered -- considerable energy and resources are needed over several years to develop the curriculum and to train tutors and students in the PBL process. Most schools need to import expertise to help initiate, develop and sustain PBL. Once up and running, a PBL curriculum can be demanding of staff time; Des Marchais estimated that the introduction of PBL at Canada's University of Sherbrooke increased the teaching load by 30%.31 However, at the University of New Mexico, PBL increased the contact time between students and staff without increasing the overall teaching load.35 The demand on teaching staff is largely determined by class size. Compared with the costs of lecture-based curricula, the relative costs of PBL-based curricula increase with increasing class size. The "break-even" point (ie, the point where the costs of PBL and conventional curricula are the same) appears to be with annual student intakes of about 4030 or 50.33 Other necessary resources for PBL include properly furnished and equipped tutorial rooms. For successful PBL, ready access to first-class library and computer facilities is a necessity rather than a luxury. Accordingly, PBL may not be economically viable for medical schools whose annual student intake exceeds 100.19 However, some large medical schools have recently introduced PBL-based courses. For example, the University of Queensland, with a medical student intake of 240, introduced a PBL-based graduate entry medical program in 1997 (D Price, Senior Lecturer in Medical Education, personal communication). It is probable that technological advances, particularly in computing and telecommunications, have enhanced the ability of large medical schools to deliver PBL-based curricula. Another possible disadvantage of PBL is its relative inefficiency -- some research suggests that PBL curricula cover about 80% of what might be accomplished in a conventional curriculum in the same period.19 There are particular concerns about students' grounding in the basic sciences, with some evidence (although confounded by uncontrolled variables, including the effects of admission policies) that students from PBL-based schools do less well than those from traditional schools in the basic science component of the US National Board Examinations.28 However, it is argued that, as much of the basic science content in traditional curricula lacks relevance and is quickly forgotten,22 it matters little that PBL students fail to learn or remember such material. PBL can also be stressful for both students and staff, at least until they become familiar with the process.30 Most students come to PBL from educational backgrounds where teachers direct learning. By contrast, PBL does not limit what students may choose to learn, and the process may provide little guidance on the best ways of achieving learning goals. Students may be concerned that their learning strategies are misdirected or inefficient. These concerns should be anticipated and addressed within PBL tutorials where students develop and refine the necessary skills. Yet one study which compared levels of student stress in a traditional and a PBL curriculum found that PBL was less stressful.36 Some teachers find that PBL is unduly demanding of their time and some are uncomfortable in small-group situations and with their role as facilitators. Tutor training is needed to address these issues. Finally, as accounts of PBL have come mainly from medical schools where it was implemented in the context of major curricular reform, with much enthusiasm and investment in the process, the "Hawthorne effect" -- where enthusiasm per se influences the outcome -- may have been operating, and it may be difficult to differentiate enthusiasm for the new curriculum from real gains in student learning. The introduction and maintenance of PBL in less fertile educational environments may be more problematic. Future directions in PBL The pendulum of educational reform is swinging away from traditional approaches and towards PBL with such momentum that further emphasis on PBL seems inevitable. Yet PBL and traditional curricula are far from incompatible, and Berkson argues that the two will gradually merge.30 As commitment to the principles of adult learning and the creation of a more stimulating and supportive learning environment become more common goals for both students and teachers, traditional curricula will face pressure to become more integrated and interactive. Resource limitations and other constraints may force some medical schools with PBL-based curricula to revert to traditional learning methods. Yet advances in educational technology (eg, teleconferencing, computer-assisted learning) may well lessen the resource demands of PBL and make it more attractive to larger institutions. PBL is not a panacea for all the current ills in medical education.34 Of the three major variables in learning -- students, teachers and curriculum -- the latter is probably the least important.37 Nevertheless, the effect of a well designed curriculum in facilitating learning should not be underestimated. The current level of enthusiasm for PBL in Australia's medical schools seems well justified. Acknowledgements The authors acknowledge the staff and students of the School of Medicine at Flinders University of South Australia for providing the context for the writing of this paper. References Kamien M. The reform of medical education. Med J Aust 1993; 158: 226-227. World Health Organization (1973). Training and preparation of teachers for schools of medicine and of allied health sciences. Geneva: World Health Organization Technical Report Series, No. 521. Muller S. 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(Received 10 Jan, accepted 4 Sep, 1997) Authors' details School of Medicine, Faculty of Health Sciences, Flinders University of South Australia, Adelaide, SA. Paul M Finucane, FRACP, Professor of Rehabilitation and Aged Care; Steve M Johnson, PhD, Senior Lecturer in Clinical Pharmacology; and David J Prideaux, PhD, Associate Professor of Medical Education, and Head, Office of Education. Reprints will not be available from the authors. Correspondence: Professor Paul M Finucane, Department of Rehabilitation and Aged Care, School of Medicine, Flinders University of South Australia, Bedford Park, SA 5042. E-mail: sfinupmATrgh.sa.gov.au ©MJA 1998 Readers may print a single copy for personal use. No further reproduction or distribution of the articles should proceed without the permission of the publisher. For permission, contact the Australasian Medical Publishing Company Journalists are welcome to write news stories based on what they read here, but should acknowledge their source as "an article published on the Internet by The Medical Journal of Australia <http://www.mja.com.au>". <URL: http://www.mja.com.au/> © 1998 Medical Journal of Australia.

Paul M Finucane · Steve M Johnson · David J Prideaux