Falls in older people are a major concern

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1 INJURY AND HARM The burden of hospitalised fall-related injury in community-dwelling older people in Victoria: a database study Trang Vu, 1 Lesley Day, 1 Caroline F. Finch 1,2 Falls in older people are a major concern to public health. 1,2 The morbidity and mortality burden from fallrelated injury in older Victorians have been previously estimated using episode-level (unlinked) hospital discharge data (HDD). 3 The economic burden of fall-related injury in this population has also been estimated using unlinked HDD and average treatment costs. 4,5 Being based on data more than two decades old, estimates of the economic burden of fall-related injury in older Victorians are out-of-date and are very likely to not reflect current hospital care patterns for fall-related injury in older people. 3 Furthermore, average treatment costs provide general cost information but do not account for patient variability, 6 while unlinked HDD have been shown to be associated with multiple counting and inaccurate incidence estimates. 7,8 None of the research cited above reported estimates for community-dwelling older people separately. 3-5 This is an important group, as they account for 73% of fall-related hospitalisations in older populations. 9 In view of the limitations of previous research, 3-5,10 the objective of this study was to estimate the burden of hospitalised fall-related injury in community-dwelling older people aged 65+ years in Victoria using linked (person-based) HDD and patient-level hospital treatment costs. Methods Hospital discharge data We used the Victorian Admitted Episode Dataset (VAED) as the source of Abstract Objective: To estimate the burden of hospitalised fall-related injury in community-dwelling older people in Victoria. Methods: We analysed fall-related, person-identifying hospital discharge data and patient-level hospital treatment costs for community-dwelling older people aged 65+ years from Victoria between 1 July 2005 and 30 June 2008, inclusive. Key outcomes of interest were length of stay (LOS)/episode, cumulative LOS (CLOS)/patient and inpatient costs. Results: The burden of hospitalised fall-related injury in community-dwelling older people aged 65+ years in Victoria was 284,781 hospital bed days in, rising to 310,031 hospital bed days in. Seventy-one per cent of episodes were multiday. One in 15 acute care episodes was a high LOS outlier and 14% of patients had 1 episode classified as high LOS outlier. The median CLOS/patient was nine days (interquartile range 2 27). The annual costs of inpatient care, in June 2009 prices, for fall-related injury in community-dwelling people aged 65+ years in Victoria rose from $213 million in to $237 million in. The burden of hospitalised fall-related injury in community-dwelling older women, people aged 85+ years and those with comorbidity was considerable. Conclusions: The burden of hospitalised fall-related injury in community-dwelling older people aged 65+ years in Victoria is significantly more than previously projected. Importantly, this study identifies that women, patients with comorbidity and those aged 85+ years account for a considerable proportion of this burden. Implications: A corresponding increase in falls prevention effort is required to ensure that the burden is properly addressed. Key words: falls, older people, length of stay, inpatient costs, hospitalisation administrative, demographic and clinical information for each inpatient episode of care in Victoria. This dataset is managed by the Victorian Department of Health (DOH) and subject to regular audits that show good-toexcellent diagnosis and procedure coding quality. 11,12 External cause of falls, hip fracture diagnosis and hip replacement, and Charlson comorbidities were included in the most recent published audits. 12 Episodes of care in the VAED with a discharge date between 1 July 2005 and 30 June 2008, inclusive (fiscal years, and ), were extracted using the process depicted in Figure 1. Records were selected if they satisfied the following criteria: age at admission 65+ years, principal mechanism of injury indicating a fall (W00 W19 in ICD-10-AM 13 ) and any discharge diagnosis indicating an injury (S00 to T75 or T79 in ICD-10-AM 13 ). Since the selected records referred to specific episodes of care rather than to cases or persons, they were internally linked using person-identifying variables (sex, date of birth, postcode, country of birth, and Medicare number and suffix) 1. Monash Injury Research Institute, Monash University, Victoria 2. Australian Centre for Research into Injury in Sport and its Prevention, Federation University Australia Correspondence to: Dr Trang Vu, Faculty of Business and Economics, Monash University, PO Box 197, Caulfield, Vic 3145; trang.vu@monash.edu Submitted: June 2013; Revision requested: August 2013; Accepted: September 2013 The authors have stated they have no conflict of interest Aust NZ J Public Health. 2014; 38:128-33; doi: / Australian and New Zealand Journal of Public Health 2014 vol. 38 no. 2

2 Injury and Harm Burden of hospitalised fall-related injury in older Victorians to produce a person-level dataset for the study. A DOH study on the quality of VAED internal linkage for the period found that the rate of incorrectly matched records was between 1% and 2%, and the percentage of unmatched inter-hospital transfer records from the same patients was 15%. 14 We retained in the person-level dataset any records with the principal diagnosis indicating an injury (S00 to T75 or T79 in ICD- 10-AM) or follow-up care of an injury (Z47, Z48, Z50 or Z75.1 in ICD-10-AM). 13 We defined community-dwelling status as living in one s own home or private accommodation and not residing in a nursing home. The admission source variable which was used to determine community-dwelling status was 99.9% complete. Hospital cost data We obtained patient-level hospital treatment costs from the Victorian Cost Weight Study (VCWS) which has linkage variables that are also present in the VAED, enabling cost data to be deterministically linked with HDD. The VCWS, conducted annually and managed by the DOH, uses clinical costing systems and cost modelling methodology to collect inpatient cost data from Victorian public hospitals. 15 Thirty-nine large metropolitan and regional public hospitals (28% of public hospitals contributing data to the VAED) provided cost data to the VCWS in. 16 Despite this limitation and non-participation by private hospitals, cost data from the VCWS have been found to be highly generalisable to costs of inpatient care across all Victorian hospitals. 6 Cost data from the National Hospital Cost Data Collection (NHCDC) were used to supplement the Victorian cost data. The NHCDC contains state and territory annual estimates of the average cost of inpatient care for a comprehensive range of Australian Refined Diagnosis Related Groups (AR-DRG). In, a total of 238 public hospitals (47% of all large public hospitals in Australia) and 82 private hospitals (36% of all private hospitals in Australia) participated in the NHCDC, providing cost data for 89% and 59% of the total acute episodes discharged within the year in public and private hospitals, respectively. The NHCDC was used because, at the time of the research, data collection training for had just commenced 17 and the NHCDC did not collect cost data from private hospitals. Figure 1: A flow chart of episode selection and linkage process. VAED episodes with a discharge date between 1 July 2005 and 30 June 2008, inclusive N = 6,344,881 episodes Keep if age 65+ years & principal mechanism of injury indicating a fall (W00 W19 in ICD-10-AM) n = 105,395 episodes Keep if any discharge diagnosis indicating an injury (S00 to T75 or T79 in ICD-10-AM) n = 103,482 episodes Perform deterministic linkage using person-identifying variables to create a person-level dataset n = 103,482 episodes in 62,026 persons Keep if principal diagnosis indicating an injury (S00 to T75 or T79 in ICD-10-AM) or follow-up care of an injury (Z47, Z48, Z50 or Z75.1 in ICD-10-AM) n = 83,227 episodes in 49,585 persons Keep if admission source coded as private residence/accommodation Final sample: 80,767 episodes in 48,107 persons ICD 10 AM: International Classification of Diseases, Tenth Revision, Australian Modification. VAED: Victorian Admitted Episode Dataset The average cost for each AR-DRG in the NHCDC for private hospitals was used to provide cost information for VAED episodes of care with the same AR-DRG from private hospitals. The average cost for each AR-DRG in the VCWS was used to impute missing cost in VAED episodes of care with the same AR-DRG from public hospitals. Thirty-seven VAED episodes, all in the fiscal year, had no AR-DRG information and were deleted from the cost analysis. The approach to imputing missing cost data described above was determined by a methods comparison study we conducted in 2009 (unpublished). The Monash University Human Research Ethics Committee granted approval for the use of the VAED and the VCWS (approval ID CF09/ ). Comorbidity assessment The assessment of comorbidity has been described in detail elsewhere. 18 Briefly, the prevalence of comorbidity in the study population was assessed using the Deyo adaptation of the Charlson comorbidity Index (CCI). 19 Other disease risk factors for falls and fractures 20 not included in the CCI were also evaluated, including osteoporosis, Parkinson s disease, visual impairment and deafness. The VAED could record up to 40 diagnosis codes. 11 The ascertainment of patient comorbidity was enhanced by defining the first multiday record as the index hospitalisation and searching this record as well as retrospectively examining previous record(s) for the presence of comorbidities. 21,22 Outcomes of interest Key outcomes of interest were length of stay (LOS) per episode, cumulative LOS (CLOS) per patient and inpatient costs. An episode of care was defined as a high LOS outlier if the LOS was more than three times the average LOS for a particular AR-DRG. 23 A patient was defined as a high LOS user if he/she had 1 high LOS outlier. The calculation of the CLOS per patient assumed that an episode admitted and discharged on the same day (same-day episodes) would use one hospital bed day vol. 38 no. 2 Australian and New Zealand Journal of Public Health 129

3 Vu, Day and Finch Article Data analysis Cost data from both the VCWS and NHCDC were inflated to June 2009 prices using the health-specific consumer price index available from the Australian Bureau of Statistics (ABS) Previous studies have used various indexes to inflate health prices. 27,28 A consensus regarding the choice of an index, however, does not exist. The VAED does not contain the date of injury, therefore, validated evidence-based criteria for identifying a fall-related incident hip fracture in the absence of date of injury were used to differentiate incident fall-related hip fractures from existing fall-related hip fractures. 29 For non-hip-fracture fall-related injuries, a standard approach for identifying an incident injury in the absence of the injury date was used. This approach excluded interhospital transfers and readmissions within 28 days of discharge. 7 Cross tabulations of patient characteristics by LOS and CLOS were performed. We evaluated equality of proportions using two-sample chi square tests of proportions, or Fisher s exact test, as appropriate. For LOS and CLOS, which were skewed continuous variables, medians were compared using nonparametric K-sample tests on the equality of medians. 30 The association between these variables and patients clinical and demographic characteristics were tested in bivariate analyses. The existence of a trend over time in hospitalised fall-related injuries was tested using a nonparametric test for trend across ordered groups developed by Cuzick. 31 All tests were two tailed. The level of significance was 5%. All analyses were conducted in Stata. 30 Results Overview Acute care hospitals in Victoria provided 80,767 episodes of care for fall-related injury in 48,107 community-dwelling older people aged 65+ years between 01 July 2005 and 30 June 2008, inclusive. Eighty-one per cent of these episodes occurred in public hospitals. Of the 48,107 patients, 79% were aged 75+ years, 76% were born in English-speaking countries, 70% were female and 72% resided in metropolitan areas of Melbourne. Twentyeight percent of patients had 1 comorbidity. Among the patients with 1 comorbidity, 67.2% had one comorbidity, 30.8% had 2 3 comorbidities and 2.0% had 4 comorbidities. A total of 44,942 patients (93.4%) had 1 fall-related incident injury admission between and. In total, 1,972 patients (4.1%) died in hospital, with 230 patients (11.7% of total deaths) dying on the day of admission. A fall-related incident hip fracture was the principal diagnosis in slightly more than one in four patients who died in hospital. Having any comorbidity was associated with more than 3 fold increase in the risk of in-hospital mortality (bivariate odds ratio (OR) 3.4, 95% confidence interval (CI) , p<0.001). Hospital costs of fall-related injury in community-dwelling older people Table 1 presents estimates of the inpatient costs of fall-related injury in communitydwelling older people in Victoria. Average AR-DRG-based costs were used to estimate the costs of 41.9% of episodes in, 51.0% of episodes in and 42.7% episodes in due to the restricted scope of the VCWS. Given that the amount of missing cost data in each year of interest was considerable, the annual number of hospital bed days is also reported in Table 1 to help with the interpretation of the costs estimates. The annual hospital costs of inpatient care for fall-related injury in community-dwelling people aged 65+ years in Victoria, in June 2009 prices, was estimated at $213 million in, increasing to about $237 million in. Over the study period, women accounted for 72.2% of total inpatient costs, the 85+ age group had the highest hospital cost burden (40.0% of total costs, 42.0% of total hospital bed days) and the age group had the lowest hospital cost burden (7.0% of total costs, 5.5% of hospital bed days). Existing and incident hip fractures accounted for only slightly more than one quarter of the annual number of episodes but were estimated to be responsible for more than 40% of the estimated annual hospital costs (Table 1). It should be noted that only two thirds of these episodes had actual cost data. Almost three quarters of the hospital cost burden of hip fractures were due to incident hip fractures. The category of acute care accounted for more than two-thirds of the annual hospital costs, the costs of rehabilitation care one-fifth of the annual hospital costs and the costs of other care categories about one-tenth of the annual hospital costs (Table 1). Costs for each care type also increased over time and were broadly in line with increases in total LOS. Given that significantly more acute care episodes had actual cost data than episodes for rehabilitation care and other care categories, estimates of the costs of acute care are probably more reliable than estimates of the costs of non-acute care categories. However, the total number of hospital bed days for the acute care category is probably an overestimate because sameday episodes accounted for 21.8% of acute care episodes compared with 0.2% each of rehabilitation episodes and episodes in other care categories. Length of stay Of the 80,767 episodes of care recorded between and, 71.3% were multiday episodes, 11.9% were overnight episodes and 16.8% were same day episodes (Table 2). Hospitals differed significantly in episode mix 90.5% of episodes in private hospitals were multiday episodes with the remainder divided equally between overnight and same day episodes whereas just 66.7% of episodes in public hospitals were multiday episodes, 19.7% were same day episodes and 13.6% were overnight episodes. Three-fifths of private hospital episodes were routine or elective admissions compared with under one-sixth of public hospital episodes. Over the three years of interest, patients had a median CLOS of nine days (interquartile range (IQR) 2 27). Women had a higher median CLOS than men 10 days (IQR 2 28) vs. 7 days (IQR 1 23), respectively, p<0.001 (nonparametric equality-of-medians test). The median CLOS increased steadily with age with patients in the 85+ age group having the highest CLOS for all age groups (12 days [IQR 3 32]). The effect of sex appeared to be independent to that of age and additive to the effect of age with women in the 85+ age group having a higher median CLOS compared to men in the same age group 13 days (IQR 3 33) vs. 9 days (IQR 1 28), respectively, p<0.001 (nonparametric equality-of-medians test). The CLOS also varied by the prevalence of comorbidity (Table 3). The 27.6% of patients with comorbidity used 35.9% of the total number of hospital bed days. The prevalence of any comorbidity and the prevalence of any of the top three comorbidities among patients diabetes, renal disease or dementia significantly increased the median CLOS (all 130 Australian and New Zealand Journal of Public Health 2014 vol. 38 no. 2

4 Injury and Harm Burden of hospitalised fall-related injury in older Victorians p values <0.001, nonparametric equality-ofmedians tests). The number of comorbidities in a patient significantly increased the average CLOS, irrespective of gender, country of birth group, marital status and hospital insurance cover (p values <0.001, Cuzick s test for trend). High length of stay outliers Nearly one in 15 acute care episodes were classified as a high LOS outlier. In , a similar proportion of episodes for rehabilitation care were classified as high LOS outliers but this declined to one in twenty in The highest proportion of high LOS outliers, >40%, was found among episodes for other care types which occurred almost exclusively in public hospitals. High length of stay patients During the period of interest 6,822 patients (14.2% of the total) had >1episode classified as high LOS outlier (range 1 4 episodes) (hereafter referred to as high LOS patients). Seventy-four percent of the high LOS patients were women. The high LOS patients accounted for 16,090 episodes (19.9% of the total number of episodes) and 358,699 bed days (39.9% of total number of bed days). The high LOS patients had a higher median CLOS than did other patients 46 days (IQR 25-71) compared with 6 days (IQR 1-20), respectively. High LOS patients were similar to other patients in terms of age, Indigenous status, in-hospital mortality and country of birth group. However, high LOS patients were less likely to be married, less likely to have hospital insurance and more likely to have comorbidity and being female than other patients (all p values <0.05). Discussion This study has used linked HDD, in conjunction with patient-level hospital costs and methodological enhancements for identifying incident hip fractures, 29 to provide the most reliable estimates of the burden of hospitalised fall-related injury in communitydwelling older people aged 65+ years in Victoria. To the best of our knowledge, this is the first study to specifically estimate the burden of fall-related hospitalisation in this population group. A comparison of our estimates with Moller s projections 5 for all older populations based on cost data suggests that the actual burden Table 1: Estimated annual costs (in June 2009 prices) of hospitalised fall-related injury in community-dwelling older people, Victoria, to. Year No. episodes No. patients a Total length of Total costs % Total costs stay b (days) $m All fall-related hospitalisations Acute care c Rehabilitation care c Other care types c 25,189 27,293 28,285 19,235 21,088 21,987 3,746 3,952 3,960 2,208 2,253 2,338 16,619 17,941 18,635 15,711 16,970 17,744 3,473 3,656 3,689 1,959 2,029 2, , , , , , ,675 80,889 82,654 82,794 61,208 69,879 69, Hip fractures 7,044 7,198 7,286 4,170 4,205 4, , , , Men 6,806 7,634 8,052 4,723 5,266 5,572 72,044 80,857 82, Women 18,383 19,659 20,233 11,896 12,675 13, , , , Age group ,061 2,138 2,222 1,483 1,635 1,663 16,087 15,806 15, Age group ,774 2,775 2,222 1,960 1,964 2,227 26,236 25,955 29, Age group ,416 4,803 4,807 2,967 3,175 3,253 48,058 50,155 50, Age group ,273 6,841 6,873 4,021 4,433 4,526 75,437 78,693 79, Age group 85+ 9,665 10,736 11,267 6,188 6,734 6, , , , a The total number of patients for the entire study period was 48,107 patients. The number of patients in this column does not add up to this total because some patients were admitted more than once over this period. b The calculation of the total length of stay assumed that same-day episodes would use one hospital bed day. Same-day episodes accounted for 16.1% of the number of episodes in, 17.2% of the number of episodes in and 17.1% of the number of episodes in. Same-day episodes accounted for 21.8% of acute care episodes, 0.2% of rehabilitation episodes and 0.2% of episodes in other care categories. c Cost data were available for 66.3% of acute care episodes, 13.5% of rehabilitation episodes and 21.5% of episodes for other care types vol. 38 no. 2 Australian and New Zealand Journal of Public Health 131

5 Vu, Day and Finch Article is considerably higher than previously anticipated. Specifically, Moller 5 projected that inpatient costs of fall-related injury in older people in Victoria would be $81 million in 2011 ($151 million in June 2009 prices). The results presented in Table 1 suggest that the annual inpatient costs of fall-related injury in older Victorians, not including nursing home residents, are more than $200 million. Moller 5 forecasted the number of fall-related episodes of care in older people in Victoria to reach 12,100 in 2011 and the resulting number of hospital bed days to reach 157,500 in the same period. The results presented in Table 1 show that for to community-dwelling older people in Victoria had more than 25,000 fall-related episodes of care per year totalling more than 280,000 hospital bed days annually. Differences between the projections by Moller 5 and the results presented in Table 1 may be explained in part by differences in methodological approaches and data sources. Nonetheless, the higher than previously forecasted burden of hospitalised fall-related injury in community-dwelling older people in Victoria suggests that a corresponding increase in falls prevention effort will be required to curb the impact on the hospital system and the community. One strategy is for fall prevention policy and practice in Victoria to be re-examined to identify opportunities for maximising gains in avoidable fall-related hospitalisation in this population and significantly reducing the burden. This process is already under way in Victoria with a partnership project between the Victorian DOH, universities and interested agencies. 32 In addition to quantifying the burden of fall-related hospitalisation in communitydwelling older people in Victoria, this study identifies demographic and clinical characteristics of patients utilising a disproportionate amount of hospital bed days for fall-related injury. These characteristics include nature of injury, age, comorbidity and female gender. All but one characteristic (nature of injury) may be useful for selecting target groups that maximise the potential gains in avoidable fall-related hospitalisation. Patients in the 85+ years age Table 2: Length of stay for fall-related injury in community-dwelling older people by hospital type, Victoria, to. Same-day episodes Overnight episodes Multiday episodes Row total All hospitals 13,596 (16.8) 9,590 (11.9) 57,581 (71.3) 80,767 Public hospitals (80.7% of total episodes) 12,851 (19.7) 8,858 (13.6) 43,459 (66.7) 65,168 Private hospitals (19.3% of total episodes) 745 (4.8) 732 (4.7) 14,122 (90.5) 15,599 Table 3: Cumulative length of stay by level of comorbidity in community-dwelling older people hospitalised for fall-related injury, Victoria, to. Prevalence Total CLOS a (days) Any comorbidity Any comorbidity No comorbidity 13,267 (27.6) 34,840 (72.4) 322,423 (35.9) 575,641 (64.1) Diabetes Diabetes 3,876 (8.1) 84,905 (9.5) No diabetes 44,231 (91.9) 813,159 (90.5) Renal disease Renal disease 2,392 (5.0) 62,020 (6.9) No renal disease 45,715 (95.0) 836,044 (93.1) Dementia Dementia 1,788 (3.7) 36,664 (4.1) No dementia 46,319 (96.3) 861,400 (95.9) Values are numbers (percentage) unless stated otherwise. CLOS: Cumulative length of stay. IQR: Interquartile range. * All p values <0.001, nonparametric equality-of-medians tests a The calculation of the CLOS assumed that same-day episodes would use one hospital bed day. Median CLOS* (IQR) (days) 15 (5 35) 7 (1 24) 12 (3 32) 8 (2 27) 17 (6 37) 8 (2 26) 12 (4 30) 9 (2 27) Number of sameday episodes 2,990 10,606 1,063 12, , ,076 group had the highest CLOS and accounted for a considerable proportion (40%) of total inpatient costs. This indicates that community-dwelling older people aged 85+ years should be a priority target group for falls prevention. Comorbidity is another patient characteristic that may be useful for selecting target groups for fall prevention in communitydwelling older people. Descriptive results presented here suggest that the prevalence of any comorbidity is associated with excess in-hospital mortality risk, elevated risk of becoming a high LOS patient and having longer CLOS. These results suggest that fall prevention should be an important component of co-ordinated care for community-dwelling older people with comorbidity. Finally, community-dwelling older women should be a particular priority target group for falls prevention because their share of the burden of hospitalised fall-related injury is considerable. Policy makers should ensure that they cater for the needs of this group and investigate whether older women s current uptake rate of falls prevention interventions is sufficient. The extent to which communitydwelling older women maintain participation in falls prevention activities over time should also be investigated. Our analysis used linked HDD to estimate the burden of hospitalised fall-related injury in community-dwelling older people aged 65+ years in Victoria. This is a significant improvement over previous research, 3,33 which used unlinked HDD. Furthermore, the analysis used validated hospital costs from the VCWS to calculate the annual costs of hospitalised fall-related injury in Victoria. This is another major improvement over previous research, 4,5 which used averaged costs. The use of internally linked HDD and validated hospital costs, in conjunction with methodological enhancements for the identification of incident hip fractures, mean that results presented in this study are as rigorous as possible and represent the best estimates available to date. The study, however, was limited by the lack of date of injury in the VAED and the incomplete coverage of Victorian hospitals by the VCWS. Both of these issues relate to limitations in the Victorian data. Another limitation of the VAED is that the category of patients in the VAED used to represent community-dwelling people includes people from prisons, armed 132 Australian and New Zealand Journal of Public Health 2014 vol. 38 no. 2

6 Injury and Harm Burden of hospitalised fall-related injury in older Victorians forces base camps/hospitals, supported residential facilities (excluding nursing homes) and special accommodation houses. Unfortunately, the VAED does not contain supplemental information to complement descriptions of accommodation categories to enable these people to be explicitly identified and removed from the dataset. Nevertheless, the number of patients hospitalised for a fall in these settings would be very small and unlikely to affect our findings. Conclusions and implications This study shows that the actual burden of hospitalised fall-related injury in communitydwelling older people aged 65+ years in Victoria is significantly more than previously projected. This new knowledge suggests that a corresponding increase in falls prevention effort is required to ensure that the burden is properly addressed. Importantly, this study also identifies that those aged 85+ years, women and patients with comorbidity account for a considerable proportion of this burden. Acknowledgement The authors thank the Victorian Department of Health for providing the data. TV was supported by an Australian Postgraduate Award scholarship. CFF was supported by a National Health and Medical Research Council (of Australia) Principal Research Fellowship (ID: ). References 1. Tinetti ME, Kumar C. The patient who falls: It s always a trade-off. JAMA. 2010;303(3): O Loughlin JL, Robitaille Y, Boivin J-F, Suissa S. Incidence of and risk factors for falls and injurious falls among the community-dwelling elderly. Am J Epidemiol. 1993;137(3): Cassell E, Clapperton A. Hazard Edition No. 67: Preventing injury in Victorian seniors aged 65 years and older. Melbourne (AUST): Victorian Injury Surveillance Unit; 2008 [cited 2009 Mar 17]. Available from: monash.edu.au/muarc/visu/index.html 4. Watson WL, Ozanne-Smith J. 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