Estimating parameters for probabilistic linkage of privacy-preserved datasets.

BACKGROUND: Probabilistic record linkage is a process used to bring together person-based records from within the same dataset (de-duplication) or from disparate datasets using pairwise comparisons and matching probabilities. The linkage strategy and associated match probabilities are often estimated through investigations into data quality and manual inspection. However, as privacy-preserved datasets comprise encrypted data, such methods are not possible. In this paper, we present a method for estimating the probabilities and threshold values for probabilistic privacy-preserved record linkage using Bloom filters. METHODS: Our method was tested through a simulation study using synthetic data, followed by an application using real-world administrative data. Synthetic datasets were generated with error rates from zero to 20% error. Our method was used to estimate parameters (probabilities and thresholds) for de-duplication linkages. Linkage quality was determined by F-measure. Each dataset was privacy-preserved using separate Bloom filters for each field. Match probabilities were estimated using the expectation-maximisation (EM) algorithm on the privacy-preserved data. Threshold cut-off values were determined by an extension to the EM algorithm allowing linkage quality to be estimated for each possible threshold. De-duplication linkages of each privacy-preserved dataset were performed using both estimated and calculated probabilities. Linkage quality using the F-measure at the estimated threshold values was also compared to the highest F-measure. Three large administrative datasets were used to demonstrate the applicability of the probability and threshold estimation technique on real-world data. RESULTS: Linkage of the synthetic datasets using the estimated probabilities produced an F-measure that was comparable to the F-measure using calculated probabilities, even with up to 20% error. Linkage of the administrative datasets using estimated probabilities produced an F-measure that was higher than the F-measure using calculated probabilities. Further, the threshold estimation yielded results for F-measure that were only slightly below the highest possible for those probabilities. CONCLUSIONS: The method appears highly accurate across a spectrum of datasets with varying degrees of error. As there are few alternatives for parameter estimation, the approach is a major step towards providing a complete operational approach for probabilistic linkage of privacy-preserved datasets.

Evaluating privacy-preserving record linkage using cryptographic long-term keys and multibit trees on large medical datasets.

BACKGROUND: Integrating medical data using databases from different sources by record linkage is a powerful technique increasingly used in medical research. Under many jurisdictions, unique personal identifiers needed for linking the records are unavailable. Since sensitive attributes, such as names, have to be used instead, privacy regulations usually demand encrypting these identifiers. The corresponding set of techniques for privacy-preserving record linkage (PPRL) has received widespread attention. One recent method is based on Bloom filters. Due to superior resilience against cryptographic attacks, composite Bloom filters (cryptographic long-term keys, CLKs) are considered best practice for privacy in PPRL. Real-world performance of these techniques using large-scale data is unknown up to now. METHODS: Using a large subset of Australian hospital admission data, we tested the performance of an innovative PPRL technique (CLKs using multibit trees) against a gold-standard derived from clear-text probabilistic record linkage. Linkage time and linkage quality (recall, precision and F-measure) were evaluated. RESULTS: Clear text probabilistic linkage resulted in marginally higher precision and recall than CLKs. PPRL required more computing time but 5 million records could still be de-duplicated within one day. However, the PPRL approach required fine tuning of parameters. CONCLUSIONS: We argue that increased privacy of PPRL comes with the price of small losses in precision and recall and a large increase in computational burden and setup time. These costs seem to be acceptable in most applied settings, but they have to be considered in the decision to apply PPRL. Further research on the optimal automatic choice of parameters is needed.

Long-term mortality among older adults with burn injury: a population-based study in Australia.

OBJECTIVE: To assess if burn injury in older adults is associated with changes in long-term all-cause mortality and to estimate the increased risk of death attributable to burn injury. METHODS: We conducted a population-based matched longitudinal study - based on administrative data from Western Australia's hospital morbidity data system and death register. A cohort of 6014 individuals who were aged at least 45 years when hospitalized for a first burn injury in 1980-2012 was identified. A non-injury comparison cohort, randomly selected from Western Australia's electoral roll (n = 25 759), was matched to the patients. We used Kaplan-Meier plots and Cox proportional hazards regression to analyse the data and generated mortality rate ratios and attributable risk percentages. FINDINGS: For those hospitalized with burns, 180 (3%) died in hospital and 2498 (42%) died after discharge. Individuals with burn injury had a 1.4-fold greater mortality rate than those with no injury (95% confidence interval, CI: 1.3-1.5). In this cohort, the long-term mortality attributable to burn injury was 29%. Mortality risk was increased by both severe and minor burns, with adjusted mortality rate ratios of 1.3 (95% CI: 1.1-1.9) and 2.1 (95% CI: 1.9-2.3), respectively. CONCLUSION: Burn injury is associated with increased long-term mortality. In our study population, sole reliance on data on in-hospital deaths would lead to an underestimate of the true mortality burden associated with burn injury.

Accuracy and completeness of patient pathways--the benefits of national data linkage in Australia.

BACKGROUND: The technical challenges associated with national data linkage, and the extent of cross-border population movements, are explored as part of a pioneering research project. The project involved linking state-based hospital admission records and death registrations across Australia for a national study of hospital related deaths. METHODS: The project linked over 44 million morbidity and mortality records from four Australian states between 1st July 1999 and 31st December 2009 using probabilistic methods. The accuracy of the linkage was measured through a comparison with jurisdictional keys sourced from individual states. The extent of cross-border population movement between these states was also assessed. RESULTS: Data matching identified almost twelve million individuals across the four Australian states. The percentage of individuals from one state with records found in another ranged from 3-5%. Using jurisdictional keys to measure linkage quality, results indicate a high matching efficiency (F measure 97 to 99%), with linkage processing taking only a matter of days. CONCLUSIONS: The results demonstrate the feasibility and accuracy of undertaking cross jurisdictional linkage for national research. The benefits are substantial, particularly in relation to capturing the full complement of records in patient pathways as a result of cross-border population movements. The project identified a sizeable 'mobile' population with hospital records in more than one state. Research studies that focus on a single jurisdiction will under-enumerate the extent of hospital usage by individuals in the population. It is important that researchers understand and are aware of the impact of this missing hospital activity on their studies. The project highlights the need for an efficient and accurate data linkage system to support national research across Australia.

Privacy-preserving record linkage on large real world datasets.

Record linkage typically involves the use of dedicated linkage units who are supplied with personally identifying information to determine individuals from within and across datasets. The personally identifying information supplied to linkage units is separated from clinical information prior to release by data custodians. While this substantially reduces the risk of disclosure of sensitive information, some residual risks still exist and remain a concern for some custodians. In this paper we trial a method of record linkage which reduces privacy risk still further on large real world administrative data. The method uses encrypted personal identifying information (bloom filters) in a probability-based linkage framework. The privacy preserving linkage method was tested on ten years of New South Wales (NSW) and Western Australian (WA) hospital admissions data, comprising in total over 26 million records. No difference in linkage quality was found when the results were compared to traditional probabilistic methods using full unencrypted personal identifiers. This presents as a possible means of reducing privacy risks related to record linkage in population level research studies. It is hoped that through adaptations of this method or similar privacy preserving methods, risks related to information disclosure can be reduced so that the benefits of linked research taking place can be fully realised.

Technical challenges of providing record linkage services for research.

BACKGROUND: Record linkage techniques are widely used to enable health researchers to gain event based longitudinal information for entire populations. The task of record linkage is increasingly being undertaken by specialised linkage units (SLUs). In addition to the complexity of undertaking probabilistic record linkage, these units face additional technical challenges in providing record linkage 'as a service' for research. The extent of this functionality, and approaches to solving these issues, has had little focus in the record linkage literature. Few, if any, of the record linkage packages or systems currently used by SLUs include the full range of functions required. METHODS: This paper identifies and discusses some of the functions that are required or undertaken by SLUs in the provision of record linkage services. These include managing routine, on-going linkage; storing and handling changing data; handling different linkage scenarios; accommodating ever increasing datasets. Automated linkage processes are one way of ensuring consistency of results and scalability of service. RESULTS: Alternative solutions to some of these challenges are presented. By maintaining a full history of links, and storing pairwise information, many of the challenges around handling 'open' records, and providing automated managed extractions are solved. A number of these solutions were implemented as part of the development of the National Linkage System (NLS) by the Centre for Data Linkage (part of the Population Health Research Network) in Australia. CONCLUSIONS: The demand for, and complexity of, linkage services is growing. This presents as a challenge to SLUs as they seek to service the varying needs of dozens of research projects annually. Linkage units need to be both flexible and scalable to meet this demand. It is hoped the solutions presented here can help mitigate these difficulties.

The effect of data cleaning on record linkage quality.

BACKGROUND: Within the field of record linkage, numerous data cleaning and standardisation techniques are employed to ensure the highest quality of links. While these facilities are common in record linkage software packages and are regularly deployed across record linkage units, little work has been published demonstrating the impact of data cleaning on linkage quality. METHODS: A range of cleaning techniques was applied to both a synthetically generated dataset and a large administrative dataset previously linked to a high standard. The effect of these changes on linkage quality was investigated using pairwise F-measure to determine quality. RESULTS: Data cleaning made little difference to the overall linkage quality, with heavy cleaning leading to a decrease in quality. Further examination showed that decreases in linkage quality were due to cleaning techniques typically reducing the variability - although correct records were now more likely to match, incorrect records were also more likely to match, and these incorrect matches outweighed the correct matches, reducing quality overall. CONCLUSIONS: Data cleaning techniques have minimal effect on linkage quality. Care should be taken during the data cleaning process.

Data linkage infrastructure for cross-jurisdictional health-related research in Australia.

BACKGROUND: The Centre for Data Linkage (CDL) has been established to enable national and cross-jurisdictional health-related research in Australia. It has been funded through the Population Health Research Network (PHRN), a national initiative established under the National Collaborative Research Infrastructure Strategy (NCRIS). This paper describes the development of the processes and methodology required to create cross-jurisdictional research infrastructure and enable aggregation of State and Territory linkages into a single linkage "map". METHODS: The CDL has implemented a linkage model which incorporates best practice in data linkage and adheres to data integration principles set down by the Australian Government. Working closely with data custodians and State-based data linkage facilities, the CDL has designed and implemented a linkage system to enable research at national or cross-jurisdictional level. A secure operational environment has also been established with strong governance arrangements to maximise privacy and the confidentiality of data. RESULTS: The development and implementation of a cross-jurisdictional linkage model overcomes a number of challenges associated with the federated nature of health data collections in Australia. The infrastructure expands Australia's data linkage capability and provides opportunities for population-level research. The CDL linkage model, infrastructure architecture and governance arrangements are presented. The quality and capability of the new infrastructure is demonstrated through the conduct of data linkage for the first PHRN Proof of Concept Collaboration project, where more than 25 million records were successfully linked to a very high quality. CONCLUSIONS: This infrastructure provides researchers and policy-makers with the ability to undertake linkage-based research that extends across jurisdictional boundaries. It represents an advance in Australia's national data linkage capabilities and sets the scene for stronger government-research collaboration.

Secure Record Linkage of Large Health Data Sets: Evaluation of a Hybrid Cloud Model.

BACKGROUND: The linking of administrative data across agencies provides the capability to investigate many health and social issues with the potential to deliver significant public benefit. Despite its advantages, the use of cloud computing resources for linkage purposes is scarce, with the storage of identifiable information on cloud infrastructure assessed as high risk by data custodians. OBJECTIVE: This study aims to present a model for record linkage that utilizes cloud computing capabilities while assuring custodians that identifiable data sets remain secure and local. METHODS: A new hybrid cloud model was developed, including privacy-preserving record linkage techniques and container-based batch processing. An evaluation of this model was conducted with a prototype implementation using large synthetic data sets representative of administrative health data. RESULTS: The cloud model kept identifiers on premises and uses privacy-preserved identifiers to run all linkage computations on cloud infrastructure. Our prototype used a managed container cluster in Amazon Web Services to distribute the computation using existing linkage software. Although the cost of computation was relatively low, the use of existing software resulted in an overhead of processing of 35.7% (149/417 min execution time). CONCLUSIONS: The result of our experimental evaluation shows the operational feasibility of such a model and the exciting opportunities for advancing the analysis of linkage outputs.

An Australian study of long-term hospital admissions and costs comparing patients with unintentional burns and uninjured people.

BACKGROUND: The objective of this study was to describe and quantify the long-term hospital service use (HSU) after burn injury and associated costs in a population-based cohort of patients with unintentional burns and compare with uninjured people. METHODS: This retrospective population-based cohort study analysed de-identified linked health administrative data of all unintentional burns patients (n = 10,460) between 2000 and 2012 in Western Australia and a matched uninjured comparison cohort (n = 42,856). HSU after burn injury (annual admission counts and cumulative length of stay) was examined. HSU costs were based on the Australian Refined Diagnosis Related Groups (AR-DRGs) code on each record. Generalised linear models were used to examine and quantify associations between burn injury and long-term HSU and associated costs. RESULTS: There were 48,728 hospitalisations after burn occurring within the study period in the burn cohort; in the uninjured comparison cohort, there were 53,244 post-study index hospitalisations. Of those in the burn cohort, 63.9% (n = 6828) had a further hospitalisation after burn injury; this compared with 40.4% (n = 17,297) in the uninjured cohort. After adjustment for socio-demographic and pre-existing health conditions the burn cohort had 2.48 times the hospitalisation rate compared to the uninjured cohort (95% CI: 2.33-2.65). The cost of post-index hospitalisations in the burn cohort totalled to $AUS248.3 million vs $AUS240.8 million in the uninjured cohort. After adjustment, the burn cohort had hospital costs 2.77 times higher than the uninjured controls (95% CI: 2.58-2.98). CONCLUSIONS: After adjustment for covariates, burn patients experienced greater hospital use for a prolonged period after the initial injury compared with uninjured people. The mean cost per episode of care was generally higher for members of the burn cohort compared to the uninjured cohort indicating either more complicated admissions or admissions for more expensive conditions.

Retrospective cohort study of health service use for cardiovascular disease among adults with and without a record of injury hospital admission.

OBJECTIVE: To quantify postinjury cardiovascular-related health service use experienced by mid to older aged adults hospitalised for injury, compared with uninjured adults. Additionally, to explore the effect of beta-blocker medications on postinjury cardiovascular hospitalisations among injury patients, given the potential cardioprotective effects of beta blockers. DESIGN: A retrospective cohort study using linked administrative and survey data. PARTICIPANTS: Records of 35 026 injured and 60 823 uninjured matched adults aged over 45 from New South Wales, Australia, who completed the 45 and up survey. PRIMARY AND SECONDARY OUTCOME MEASURES: Admission rates and cumulative lengths of stay for cardiovascular hospitalisations, and prescription rates for cardiovascular medications. Negative binomial and Cox proportional hazards regression modelling were used to generate incident rate ratios (IRRs) and HR. RESULTS: Compared with the uninjured, those with injury had a 19% higher adjusted rate of postinjury cardiovascular admissions (IRR 1.19, 95% CI 1.14 to 1.25), spent 40% longer in hospital for ardiovascular disease (IRR 1.40, 95% CI 1.26 to 1.57) and had slightly higher cardiovascular prescription rates (IRR 1.04, 95% CI 1.02 to 1.06), during study follow-up. Those in the injury cohort that used beta blockers both prior to and after injury (continuous) appeared to have reduced need for post-injury cardiovascular hospitalisation (IRR 1.09, 95% CI 1.17 to 1.42) compared with those commencing on beta blockers after injury (after 30 days: IRR 1.69, 95% CI 1.37 to 2.08). CONCLUSIONS: Apparent increased postinjury hospitalisation rates and prolonged length of stay related to cardiovascular disease suggest that injury patients may require clinical support for an extended period after injury. Additionally, injury patients who were on continuous beta blocker treatment appeared to have lower need for post-injury cardiovascular hospitalisations. However, the data do not allow us to draw clear conclusions and further clinical research is required.

Burn induced nervous system morbidity among burn and non-burn trauma patients compared with non-injured people.

OBJECTIVE: Burns cause acute damage to the peripheral nervous system with published reports identifying that neurological changes after injury remain for a prolonged period. To shed some light on potential mechanisms, we assessed injury etiology and patterns of nervous system morbidity after injury by comparing long-term hospital admissions data of burns patients and other non-burn trauma patients with uninjured people. METHODS: Linked hospital and death data of a burn patient cohort (n=30,997) in Western Australia during the period 1980-2012 were analysed along with two age and gender frequency matched comparison cohorts: non-burn trauma patients (n=28,647) and; non-injured people (n=123,399). The number of annual NS disease admissions and length of stay (LOS) were used as outcome measures. Multivariable negative binomial regression modelling was used to derive adjusted incidence rate ratios and 95% confidence intervals (IRR, 95% CI) and adjusted Cox regression models and hazard ratios (HR) were used to examine time to first nervous system admission after burn and incident admission rates. RESULTS: The most common peripheral nervous system condition identified in each cohort (burn, non-burn trauma, uninjured) were episodic and paroxysmal disorders followed by nerve root and plexus disorders and polyneuropathies/peripheral NS conditions. Significantly elevated admission rates for NS conditions (IRR, 95% CI) were found for the burn (2.20, 1.86-2.61) and non-burn trauma (1.85, 1.51-2.27), compared to uninjured. Peripheral nervous system admission rates after injury (IRR, 95% CI) were significantly higher regardless of age at time of injury for the burn (<15years: 1.97, 1.49-2.61; 15-45: 2.70, 2.016-3.55; ≥45year: 1.62, 1.33-1.97) and non-burn trauma cohorts (<15years: 1.91, 1.55-2.35; 15-45: 1.94, 1.51-2.49; ≥45year: 1.42, 1.18-1.72), when compared to the uninjured. Significantly higher rates of incident NS hospitalisations were found for the burn cohort vs. uninjured cohort for a period of 15-years after discharge (0-5 years: HR, 95% CI: 1.97, 1.75-2.22; 5-15 years; HR, 95% CI: 1.44, 1.28-1.63). The non-burn trauma cohort had significantly higher incident nervous system admissions for 10 years after discharge (0-30 days: HR, 95% CI: 4.75, 2.44-9.23; 30days to 1-year HR, 95% CI: 2.95, 2.34-3.74; 1-5 years; HR, 95% CI: 1.47, 1.26-1.70; 5-10 years; HR, 95% CI: 1.34, 1.13-1.58). CONCLUSIONS: Results suggest that injury patients are at increased risk of peripheral nervous system morbidity after discharge for a prolonged period of time. The time patterns associated with incident nervous system conditions suggest possible differences in underlying pathology and long-term patient care needs. Further research is needed to elucidate the underlying neuropathology.

Long-term mental health outcomes after unintentional burns sustained during childhood: a retrospective cohort study.

BACKGROUND: Burns are a devastating injury that can cause physical and psychological issues. Limited data exist on long-term mental health (MH) after unintentional burns sustained during childhood. This study assessed long-term MH admissions after paediatric burns. METHODS: This retrospective cohort study included all children (< 18 years) hospitalised for a first burn (n = 11,967) in Western Australia, 1980-2012, and a frequency matched uninjured comparison cohort (n = 46,548). Linked hospital, MH and death data were examined. Multivariable negative binomial regression modelling was used to generate incidence rate ratios (IRR) and 95% confidence intervals (CI). RESULTS: The burn cohort had a significantly higher adjusted rate of post-burn MH admissions compared to the uninjured cohort (IRR, 95% CI: 2.55, 2.07-3.15). Post-burn MH admission rates were twice as high for those younger than 5 years at index burn (IRR, 95% CI 2.06, 1.54-2.74), three times higher for those 5-9 years and 15-18 years (IRR, 95% CI: 3.21, 1.92-5.37 and 3.37, 2.13-5.33, respectively) and almost five times higher for those aged 10-14 (IRR, 95% CI: 4.90, 3.10-7.76), when compared with respective ages of uninjured children. The burn cohort had higher admission rates for mood and anxiety disorders (IRR, 95% CI: 2.79, 2.20-3.53), psychotic disorders (IRR, 95% CI: 2.82, 1.97-4.03) and mental and behavioural conditions relating to drug and alcohol abuse (IRR, 95% CI: 4.25, 3.39-5.32). CONCLUSIONS: Ongoing MH support is indicated for paediatric burn patients for a prolonged period after discharge to potentially prevent psychiatric morbidity and associated academic, social and psychological issues.

A population-based comparison study of the mental health of patients with intentional and unintentional burns.

BACKGROUND: A number of studies report high prevalence of mental health conditions among burn patients. However there is a need to understand differences in the temporal relationship between mental health conditions and intentional and unintentional burns to hasten psychological prevention and intervention. This study aims to compare the socio-demographic profile, burn characteristics and pre- and post-burn psychiatric morbidity of burn patients by intent-of-injury. METHODS: De-identified linked hospital, death and mental health (MH) case registry data of burn patients hospitalised in Western Australia between 1 January 1980 and 30 June 2012 were analysed. Crude (observed) post-burn rates of mental health admissions were generated by burn intent-of-injury. Descriptive statistics were performed to compare the characteristics of the burn patients. RESULTS: A total of 30,997 individuals were hospitalised for a first burn; 360 (1.2%) had self-harm burns and 206 (0.7%) assault burns. Over the study period, admission rates for assault burns increased by 4.8% per year (95% confidence interval (CI) 3.1-6.5%) and self-harm burns increased 6.9% per year (95% CI 4.8-9.1%). Self-harm and assault burns occurred mainly among those aged 15 to 44 years (median age, interquartile range (IQR): self-harm 30 years, 22-40; assault 31 years, 23-38). Those with self-harm burns had a longer index hospital stay (median (IQR): self-harm 15 days (5-35) vs 4 days (1-11) assault vs 4 days (1-10) unintentional) and higher in-hospital mortality (7.2% self-harm vs 1.9% assault burns vs 0.8% unintentional). More than half (55.0%) of self-harm burns had a prior hospitalisation (5-year lookback) for a MH condition vs 10.7% of assault burns and 2.8% of unintentional burns. Crude post-burn rates of MH admissions per 100 person-years (PY) by intent-of-burn subgroups: self-harm 209 per 100 PY, assault burns 11 per 100 PY and unintentional burns 3 per 100 PY. CONCLUSIONS: Intentional burn patients experienced significantly higher pre- and post-burn mental health morbidity along with significant adverse outcome in comparison with unintentional burns. Early psychological assessment and intervention could help in improving the MH of these patients.

Diabetes mellitus after injury in burn and non-burned patients: A population based retrospective cohort study.

OBJECTIVE: To compare hospitalisations for diabetes mellitus (DM) after injury experienced by burn patients, non-burn trauma patients and people with no record of injury admission, adjusting for socio-demographic, health and injury factors. METHODS: Linked hospital and death data for a burn patient cohort (n=30,997) in Western Australia during the period 1980-2012 and two age and gender frequency matched comparison cohorts: non-burn trauma patients (n=28,647); non-injured people (n=123,399). The number of DM admissions and length of stay were used as outcome measures. Multivariate negative binomial regression was used to derive adjusted incidence rate ratios and 95% confidence intervals (IRR, 95%CI) for overall post-injury DM admission rates. Multivariate Cox regression models and hazard ratios (HR) were used to examine time to first DM admission and incident admission rates after injury discharge. RESULTS: The burn cohort (IRR, 95%: 2.21, 1.80-2.72) and other non-burn trauma cohort (IRR, 95%CI: 1.63, 1.24-2.14) experienced significantly higher post-discharge admission rates for DM than non-injured people. Compared with the non-burn trauma cohort, the burn cohort experienced a higher rate of post-discharge DM admissions (IRR, 95%CI: 1.40, 1.07-1.84). First-time DM admissions were significantly higher during first 5-years after-injury for the burn cohort compared with the non-burn trauma cohort (HR, 95%CI: 2.00, 1.31-3.05) and non-injured cohort (HR, 95%CI: 1.96, 1.46-2.64); no difference was found >5years (burn vs. non-burn trauma: HR, 95%CI: 0.88, 0.70-1.12; burn vs non-injured: 95%CI: 1.08 0.82-1.41). No significant difference was found when comparing the non-burn trauma and non-injured cohorts (0-5 years: HR, 95%CI: 1.03, 0.71-1.48; >5years: HR. 95%CI: 1.11, 0.93-1.33). CONCLUSIONS: Burn and non-burn trauma patients experienced elevated rates of DM admissions after injury compared to the non-injured cohort over the duration of the study. While burn patients were at increased risk of incident DM admissions during the first 5-years after the injury this was not the case for non-burn trauma patients. Sub-group analyses showed elevated risk in both adult and pediatric patients in the burn and non-burn trauma. Detailed clinical data are required to help understand the underlying pathogenic pathways triggered by burn and non-burn trauma. This study identified treatment needs for patients after burn and non-burn trauma for a prolonged period after discharge.

A retrospective cohort study to compare post-injury admissions for infectious diseases in burn patients, non-burn trauma patients and uninjured people.

BACKGROUND: Injury triggers a range of systemic effects including inflammation and immune responses. This study aimed to compare infectious disease admissions after burn and other types of injury using linked hospital admissions data. METHODS: A retrospective longitudinal study using linked health data of all patients admitted with burns in Western Australia (n = 30,997), 1980-2012, and age and gender frequency matched cohorts of people with non-burn trauma (n = 28,647) and no injury admissions (n = 123,399). Analyses included direct standardisation, negative binomial regression and Cox proportional hazards regression. RESULTS: Annual age-standardised infectious disease admission rates were highest for the burn cohort, followed by the non-burn trauma and uninjured cohorts. Age-standardised admission rates by decade showed different patterns across major categories of infectious diseases, with the lower respiratory and skin and soft tissue infections the most common for those with burns and other open trauma. Compared with the uninjured, those with burns had twice the admission rate for infectious disease after discharge (incident rate ratio (IRR), 95% confidence interval (CI): 2.04, 1.98-2.11) while non-burn trauma experienced 1.74 times higher rates (95%CI: 1.68-1.81). The burn cohort experienced 10% higher rates of first-time admissions after discharge when compared with the non-burn trauma (hazard ratio (HR), 95%CI: 1.10, 1.05-1.15). Compared with the uninjured cohort, incident admissions were highest during the first 30 days after discharge for burns (HR, 95%CI: 5.18, 4.15-6.48) and non-burn trauma (HR, 95%CI: 5.06, 4.03-6.34). While incident rates remained high over the study period, the magnitude decreased with increasing time from discharge: burn vs uninjured: HR, 95%CI: 30 days to 1 year: 1.69, 1.53-1.87; 1 to 10 years: 1.40, 1.33-1.47; 10 years to end of study period: 1.16, 1.08-1.24; non-burn trauma vs uninjured: HR, 95%CI: 30 days to 1 year: 1.71, 1.55-1.90; 1 to 10 years: 1.30, 1.24-1.37; 10 years to end of study period: 1.09, 1.03-1.17). CONCLUSIONS: Burns and non-burn trauma patients had higher admission rates for infectious diseases compared with age and gender matched uninjured people. The pattern of annual admission rates for major categories of infectious diseases varied across injury groups. Overall, the burn cohort experienced the highest rates for digestive, lower respiratory and skin and soft tissue infections. These results suggest long-term vulnerability to infectious disease after injury, possibly related to long-term immune dysfunction.

A population-based retrospective cohort study to assess the mental health of patients after a non-intentional burn compared with uninjured people.

BACKGROUND: The objective of this study was to describe and quantify mental health (MH) admissions experienced by patients with unintentional burns subsequent to their injury. METHODS: A retrospective population-based cohort study that used de-identified linked hospital, death and mental health in-patient case registry data of all burn patients hospitalised for unintentional burns (n=10,460) between 2000 and 2012 in Western Australia and an age and gender matched uninjured comparison cohort (n=42,856). Cohorts had a median age at study index of 26 years with males comprising 66% of each cohort. MH admissions for 5 years before and after the injury were examined. Negative binomial and Cox proportional hazards regressions were adjusted for socio-demographic and pre-existing health conditions and used to quantify associations between burns and MH hospitalisations. RESULTS: In the burn cohort during the 5-year post-burn period, 4% had a MH admission, 2% were admitted for self-harm, and 3% were admitted for a behavioural disorder caused by drugs/alcohol. Significantly elevated adjusted admission rates for MH conditions were observed for the burn cohort compared with the uninjured cohort (IRR, 95% CI: 4.89, 3.52-6.79). Increased MH admission rates were found for all age groups but were most pronounced in those younger than 18 years of age at time of burn (IRR, 95% CI: 6.28, 3.00-13.14), followed by those aged 18-60 (5.14, 3.59-7.35) and those over 60 years (IRR, 95% CI: 2.97, 1.38-6.39) compared to the uninjured cohort. Gender-specific analyses showed significant differences for male (IRR, 95% CI: 4.48, 3.05-6.59) and female burn patients (IRR, 95% CI: 6.00, 3.62-9.92), compared to uninjured. The burn cohort had higher adjusted first time admissions for MH conditions (HR, 95% CI: 3.55, 2.72-4.64), mood and anxiety disorders (HR, 95% CI: 3.77, 2.81-5.08), psychotic disorders (HR, 95% CI: 3.55, 1.99-6.15) and behavioural disorders related to alcohol/drugs (HR, 95% CI: 4.75, 3.09-7.28) for five years after the initial burn. CONCLUSIONS: Patients hospitalised for unintentional burns had significantly higher MH admission rates after discharge than that observed for an uninjured cohort. Ongoing mental health support is clearly indicated for many burns patients for a prolonged period after discharge.

Geographic distribution of burn in an Australian setting.

OBJECTIVE: To investigate the geographic distribution and temporal trends of burn admissions in an Australian setting. METHODS: Health administrative data of all persons hospitalised for a first burn in Western Australia for the period 2000-2012 were used. Crude and standardised incident rates were generated for each region. Maps of crude rates were generated for state regions and postcode-suburbs of Perth, the capital city. Standardised incidence rates were generated for Western Australia, total and regions, and for sub-cohorts defined by age (<20years; ≥20 years), TBSA burn severity and major causes of burns (fire, scalds and contact). Negative binomial regression was used to examine temporal changes and generate incidence rate ratios (IRR) with 95% confidence intervals (CI). RESULTS: Perth had the lowest burn admission rate per population; clusters of suburbs of lower social advantage and higher immigrant settlement were identified as being at high risk. While the highest observed admission rates were found in Kimberley and Goldfields (remote) regions, after adjustment for the regional demographic structures, the Wheatbelt and Mid-West (rural) regions were found to have the highest adjusted rates of burn admissions. Significant annual declines in admission rates were found for the Kimberley, Pilbara and Goldfields (remote regions); however, stable admission rates were identified for all other regions. CONCLUSIONS: The Mid-West and Wheatbelt rural regions were found to have the highest risk of burn admissions raising concerns about farming-related injury. Safety awareness and burn prevention strategies need to be continued, with specific attention to these high risk areas, to reduce burn admissions in Western Australia.

Effects of Pediatric Burns on Gastrointestinal Diseases: A Population-Based Study.

The systemic responses triggered by burns have been shown to include effects on the gastrointestinal tract. However, it is not clear if these changes lead to long-term gastrointestinal morbidity in patients with burns. The aim of this study was to assess if pediatric burns are associated with increased hospital use for gastrointestinal diseases after discharge for the initial injury. A population-based longitudinal study was performed using linked hospital and death data from Western Australia for children younger than 15 years when hospitalized for a first burn injury (n = 10,436) between 1980 and 2012, along with a frequency-matched noninjury comparison cohort, randomly selected from Western Australia's birth registrations (n = 40,819). Crude admission rates and cumulative length of stay for digestive diseases were calculated. Negative binomial and Cox proportional hazards regression modeling were used to generate incidence rate ratios (IRRs) and hazard ratios, respectively. After discharge, the pediatric burn cohort experienced twice the rate of gastrointestinal disease admissions (IRR, 95% confidence interval [CI]: 2.03, 1.56-2.65), spent over twice as long in hospital (IRR, 95% CI: 2.23, 1.67-2.98), and had a higher rate of first-time or incident gastrointestinal disease admissions (hazard ratio, 95% CI: 1.18, 1.08-1.29) when compared with the uninjured cohort, after adjusting for demographic and preexisting health factors. Children who experience a burn injury hospitalization are at increased risk of postburn hospital service use for gastrointestinal diseases when compared with uninjured children.

Burns and long-term infectious disease morbidity: A population-based study.

BACKGROUND: There is a growing volume of data that indicates that serious injury suppresses immune function, predisposing individuals to infectious complications. With recent evidence showing long-term immune dysfunction after less severe burn, this study aimed to investigate post-burn infectious disease morbidity and assess if burn patients have increased long-term hospital use for infectious diseases. METHODS: A population-based longitudinal study using linked hospital morbidity and death data from Western Australia for all persons hospitalised for a first burn (n=30,997) in 1980-2012. A frequency matched non-injury comparison cohort was randomly selected from Western Australia's birth registrations and electoral roll (n=123,399). Direct standardisation was used to assess temporal trends in infectious disease admissions. Crude annual admission rates and length of stay for infectious diseases were calculated. Multivariate negative binomial and Cox proportional hazards regression modeling were used to generate adjusted incidence rate ratios (IRR) and hazard ratios (HR), respectively. RESULTS: After adjustment for demographic factors and pre-existing health status, the burn cohort had twice (IRR, 95% confidence interval (CI): 2.04, 1.98-2.22) as many admissions and 3.5 times the number of days in hospital (IRR, 95%CI: 3.46, 3.05-3.92) than the uninjured cohort for infectious diseases. Higher rates of infectious disease admissions were found for severe (IRR, 95%CI: 2.37, 1.89-2.97) and minor burns (IRR, 95%CI: 2.22, 2.11-2.33). Burns were associated with significantly increased incident admissions: 0-30days (HR, 95%CI: 5.18, 4.15-6.48); 30days-1year (HR, 95%CI: 1.69, 1.53-1.87); 1-10 years (HR, 95%CI: 1.40:1.33-1.47); >10years (HR, 95%CI: 1.16, 1.08-1.24). Respiratory, skin and soft tissue and gastrointestinal infections were the most common. The burn cohort had a 1.75 (95%CI: 1.37-2.25) times greater rate of mortality caused by infectious diseases during the 5-year period after discharge than the uninjured cohort. CONCLUSIONS: These findings suggest that burn has long-lasting effects on the immune system and its function. The increase in infectious disease in three different epithelial tissues in the burn cohort suggests there may be common underlying pathophysiology. Further research to understand the underlying mechanisms are required to inform clinical interventions to mitigate infectious disease after burn and improve patient outcomes.