Abstract

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.

Résumé

Objectif

Évaluer si les brûlures, chez les adultes âgés, sont associées à un changement de la mortalité à long terme toutes causes confondues et estimer la majoration du risque de décès attribuable aux brûlures.

Méthodes

Nous avons réalisé une étude longitudinale appariée en population, à partir de données administratives extraites des registres de décès et du système de données sur la morbidité des hôpitaux d'Australie occidentale. Une cohorte de 6 014 individus, âgés d'au moins 45 ans au moment de leur première hospitalisation pour brûlures, sur la période de 1980 à 2012, a été identifiée. Une cohorte comparative d'individus n'ayant pas souffert de brûlures a été aléatoirement sélectionnée dans les listes électorales d'Australie occidentale (n = 25 759) pour appariement avec la cohorte des patients victimes de brûlures. Nous avons utilisé des courbes de Kaplan-Meier et une régression des risques proportionnels de Cox pour analyser les données et obtenir les ratios des taux de mortalité et les pourcentages de risque attribuable.

Résultats

Dans la cohorte des personnes hospitalisées pour brûlures, 180 personnes (3 %) sont décédées à l'hôpital et 2 498 personnes (42 %) sont décédées après leur sortie de l'hôpital. Nous avons trouvé un taux de mortalité 1,4 fois supérieur pour les victimes de brûlures comparativement aux individus non victimes de brûlures (intervalle de confiance de 95 % : 1,3-1,5). Dans cette cohorte, la mortalité à long terme attribuable aux brûlures a été de 29 %. Le risque de mortalité a été majoré à la fois en cas de brûlures graves et de brûlures mineures, avec des ratios de taux de mortalité ajustés de 1,3 (IC de 95 % : 1,1-1,9) et 2,1 (IC de 95 % : 1,9-2,3) respectivement.

Conclusion

Les brûlures sont associées à une majoration de la mortalité à long terme. Dans la population étudiée, l'utilisation exclusive des données relatives aux décès survenus dans les hôpitaux aurait entraîné une sous-estimation de la vraie charge de mortalité associée aux brûlures.

Resumen

Objetivo

Evaluar si las quemaduras en adultos de edad avanzada están asociadas con los cambios en la mortalidad por todas las causas a largo plazo y estimar el aumento del riesgo de muerte atribuible a las quemaduras.

Métodos

Se llevó a cabo un estudio poblacional longitudinal emparejado sobre la base de datos administrativos proporcionados por el sistema de datos de morbilidad y el registro de defunciones de los hospitales de Australia Occidental. Se identificó una cohorte de 6014 individuos que tenían como mínimo 45 años cuando fueron hospitalizados por una primera quemadura entre 1980 y 2012. Se comparó una cohorte de personas que no habían sufrido quemaduras seleccionadas aleatoriamente del censo electoral de Australia Occidental (n=25 759) con los pacientes. Se utilizaron el método de Kaplan-Meier y la regresión de Cox de riesgos proporcionales para analizar los datos, las razones de tasas de mortalidad generados y los porcentajes de riesgo atribuible.

Resultados

De todos los hospitalizados con quemaduras, 180 (el 3%) murieron en el hospital y 2498 (el 42%) murieron después de haber sido dados de alta. Los individuos con quemaduras tenían una tasa de mortalidad 1,4 veces mayor a la de los individuos sin quemaduras (intervalo de confianza, IC, del 95%: 1,3-1,5). En esta cohorte, la mortalidad a largo plazo atribuible a las quemaduras resultó ser del 29%. El riesgo de mortalidad se incrementó tanto por quemaduras graves como por quemaduras leves, con unas razones de tasas de mortalidad ajustadas de 1,3 (IC del 95%: 1,1-1,9) y 2,1 (IC del 95%: 1,9-2,3), respectivamente.

Conclusión

Las quemaduras están asociadas al aumento de la mortalidad a largo plazo. En nuestra población de estudio, confiar exclusivamente en los datos relativos a las muertes en hospitales llevaría a una subestimación de la verdadera carga de mortalidad asociada con las quemaduras.

ملخص

الغرض

تقييم ما إذا كانت إصابات الحروق في البالغين الأكبر سنًا مرتبطة بتغيرات في معدَّل الوفيات لجميع الأسباب على المدى الطويل وتقدير الاختطار الزائد للموت الذي يعزى إلى الإصابات الناتجة عن الحروق.

الطريقة

أجرينا دراسة طولانية مطابقة قائمة على السكان - تستند إلى البيانات الإدارية المأخوذة من نظام بيانات المراضة وسجل الوفيات الخاص بمستشفيات ولاية أستراليا الغربية. تم تحديد مجموعة من 6014 من الأفراد البالغ أعمارهم 45 سنة على الأقل عند إدخالهم إلى المستشفى للعلاج من إصابات الحروق للمرة الأولى من عام 1980 إلى عام 2012. تمت مطابقة دراسة حشدية مقارنة لغير الإصابات والتي تم اختيارها عشوائيًا من السجل الانتخابي في ولاية أستراليا الغربية (العدد = 25 759) مع المرضى. ولقد استخدمنا مخططات كابلان-ماير ونماذج تحوف المخاطر التناسبية لكوكس لتحليل البيانات ونسب معدلات الوفيات المستحدثة والنسب المئوية للأخطار التي تعزى إليها.

النتائج

بالنسبة للأشخاص الذين تم إدخالهم إلى المستشفى للعلاج من الإصابة بالحروق، توفى 180 (بنسبة 3‏ %) شخصًا منهم في المستشفى وتوفى 2498 (بنسبة ‏‏42‏ %) شخصًا بعد خروجهم من المستشفى. وكان معدل وفيات الأفراد الذين يعانون من إصابات الحروق أكبر بـ1.4 مرة من هؤلاء الأفراد الذين لا يعانون من أي إصابة (بنسبة أرجحية مقدارها ‏95‏ %: 1.3-1.5). في هذه المجموعة، كانت نسبة الوفيات طويلة الأمد التي تعزى إلى إصابات الحروق قد بلغت 29‏ %. ولقد زاد اختطار الوفيات جراء الإصابة بكلاً من الحروق الوخيمة والخفيفة مع نسب معدلات الوفيات المصححة من 1.3 (بنسبة أرجحية مقدارها ‏95‏‏ %: 1.1-1.9) و2.1 (بنسبة أرجحية مقدارها 95‏‏ %: 1.9-2.3)، على التوالي.

الاستنتاج

ترتبط إصابات الحروق بزيادة نسبة الوفيات طويلة الأمد. في دراسة السكان التي أجريناها، وجدنا أن الاكتفاء بالاتكال على البيانات الصادرة عن حالات الوفيات في داخل المستشفى قد يؤدي إلى التقليل من تقدير عبء معدلات الوفيات الحقيقية المرتبطة بإصابات الحروق.

摘要

目的

旨在评估老年人群的烧伤情况是否与各种原因造成的长期死亡率的变化有关，并估计因烧伤而增加的死亡风险。

方法

我们开展了一项以人群为基础的配对式纵向研究--基于从西澳大利亚的医院发病率数据系统和死亡登记处采集的管理数据。现已确定有 6014 个人 1980 - 2012 年期间因首次烧伤而住院且年龄至少为 45 岁。从西澳大利亚的选民名册 (n= 25 759) 中随机选择的非受伤对比人群与患者相匹配。我们采用了 Kaplan-Meier 法和 Cox 比例风险回归法来分析数据和产生的死亡比率以及归属原因的风险百分比。

结果

在那些因烧伤而住院的人群中，180 (3%) 名在医院死亡，2498 (42%) 名在出院后死亡。烧伤个人的死亡率比非受伤人群的死亡率高 1.4 倍（95% 置信区间，CI：1.3 - 1.5）。在该类人群中，因烧伤造成的长期死亡率为 29%。死亡风险因严重烧伤和轻微烧伤而增加，调整后的死亡比率分别为 1.3 (95% CI:1.1 - 1.9) 和 2.1 (95% CI:1.9 - 2.3)。

结论

烧伤与长期死亡率的增加有关。在我们的研究人群中，单纯依靠院内死亡数据将会导致在因烧伤造成的死亡率方面低估真正的量。

Резюме

Цель.

Оценка вероятной связи ожоговых травм у пациентов преклонного возраста с изменениями показателей общей смертности в отдаленном периоде, а также оценка повышенного риска смертельного исхода в результате ожоговой травмы.

Методы.

Проведено популяционное сравнительное продольное исследование на основании административных данных о заболеваемости и книг регистрации актов смерти больницы Западной Австралии. Была определена группа из 6014 человек, в которую входили лица старше 45 лет, госпитализированные с первой ожоговой травмой за период с 1980 по 2012 год. Контрольная группа без травм, выбранная произвольно из списка избирателей Западной Австралии (n = 25 759), сравнивалась с данными пациентов. Для анализа данных, полученных коэффициентов смертности и процентов добавочного риска использовались диаграммы Каплана-Мейера и регрессивный анализ пропорциональных рисков Кокса.

Результаты.

Из пациентов, госпитализированных с ожогами, 180 человек (3%) умерли в больнице и 2498 человек (42%) умерли после выписки из больницы. Лица с ожоговыми травмами имели в 1,4 раза больший коэффициент смертности, чем их соотечественники, не имевшие травм (доверительный интервал 95%, CI: 1,3-1,5). В этой группе смертность в отдаленном периоде, приписываемая ожоговым травмам, составила 29%. Риск смертности возрастал как при тяжелых, так и при легких ожогах, коэффициент смертности равнялся 1,3 (95% CI: 1,1-1,9) и 2,1 (95% CI: 1,9-2,3) соответственно.

Вывод.

Ожоговые травмы связаны с ростом показателей смертности в отдаленном периоде. Что касается популяции нашего исследования, то использование исключительно данных больничной смертности приводит к недооценке истинного коэффициента смертности, связанного с ожоговыми травмами.

Introduction

Burn injury is an important cause of morbidity and mortality worldwide, particularly among older adults.¹1 . Ho WS, Ying SY, Chan HH. A study of burn injuries in the elderly in a regional burn centre. Burns. 2001 Jun;27(4):382-5. http://dx.doi.org/10.1016/S0305-4179(00)00146-7PMID:11348749
http://dx.doi.org/10.1016/S0305-4179(00)... ⁶6 . Bessey PQ, Arons RR, Dimaggio CJ, Yurt RW. The vulnerabilities of age: burns in children and older adults. Surgery. 2006 Oct;140(4):705-15, discussion 715-7. http://dx.doi.org/10.1016/j.surg.2006.07.029PMID:17011919
http://dx.doi.org/10.1016/j.surg.2006.07... In high-income countries, where older adults form an increasingly large proportion of the population, the incidence of burn injury is likely to increase. ⁷7 . Ageing and transport. Mobility needs and safety issues. Paris: Organisation for Economic Co-operation and Development; 2001. Compared with burn injuries in younger individuals, burn injuries in older adults cause increased physical impairment, reductions in the quality of life, loss of independence and increased mortality.⁸8 . Klein MB, Lezotte DC, Heltshe S, Fauerbach J, Holavanahalli RK, Rivara FP, et al. Functional and psychosocial outcomes of older adults after burn injury: results from a multicenter database of severe burn injury.. J Burn Care Res 2011 Jan-Feb;32(1):66-78. http://dx.doi.org/10.1097/BCR.0b013e318203336aPMID:21124232
http://dx.doi.org/10.1097/BCR.0b013e3182... ⁹9 . Lundgren RS, Kramer CB, Rivara FP, Wang J, Heimbach DM, Gibran NS, et al. Influence of comorbidities and age on outcome following burn injury in older adults.. J Burn Care Res 2009 Mar-Apr;30(2):307-14. http://dx.doi.org/10.1097/BCR.0b013e318198a416PMID:19165104
http://dx.doi.org/10.1097/BCR.0b013e3181...

Improvements in the understanding of the pathophysiology of burns over the past decades have led to advances in medical and surgical treatment. The probability that an older adult is discharged alive after admission for an acute burn appears to be increasing.²2 . Lionelli GT, Pickus EJ, Beckum OK, Decoursey RL, Korentager RA. A three decade analysis of factors affecting burn mortality in the elderly. Burns. 2005 Dec;31(8):958-63. http://dx.doi.org/10.1016/j.burns.2005.06.006PMID:16269217
http://dx.doi.org/10.1016/j.burns.2005.0... ³3 . McGwin G Jr, Cross JM, Ford JW, Rue 3rd. LW Long-term trends in mortality according to age among adult burn patients. J Burn Care Rehabil. 2003 Jan-Feb;24(1):21-5. http://dx.doi.org/10.1097/00004630-200301000-00006PMID:12543987
http://dx.doi.org/10.1097/00004630-20030... ¹⁰10 . Pomahac B, Matros E, Semel M, Chan RK, Rogers SO, Demling R, et al. Predictors of survival and length of stay in burn patients older than 80 years of age: does age really matter?. J Burn Care Res 2006 May-Jun;27(3):265-9. http://dx.doi.org/10.1097/01.BCR.0000216795.90646.4EPMID:16679891
http://dx.doi.org/10.1097/01.BCR.0000216... However, compared with younger people, older adults with burn injury are still more likely to die in the year⁸8 . Klein MB, Lezotte DC, Heltshe S, Fauerbach J, Holavanahalli RK, Rivara FP, et al. Functional and psychosocial outcomes of older adults after burn injury: results from a multicenter database of severe burn injury.. J Burn Care Res 2011 Jan-Feb;32(1):66-78. http://dx.doi.org/10.1097/BCR.0b013e318203336aPMID:21124232
http://dx.doi.org/10.1097/BCR.0b013e3182... ¹¹11 . Lundgren RS, Kramer CB, Rivara FP, Wang J, Heimbach DM, Gibran NS, et al. Influence of comorbidities and age on outcome following burn injury in older adults.. J Burn Care Res 2009 Mar-Apr;30(2):307-14. http://dx.doi.org/10.1097/BCR.0b013e318198a416PMID:19165104
http://dx.doi.org/10.1097/BCR.0b013e3181... or two years¹²12 . Mandell SP, Pham T, Klein MB. Repeat hospitalization and mortality in older adult burn patients.. J Burn Care Res 2013 Jan-Feb;34(1):e36-41. http://dx.doi.org/10.1097/BCR.0b013e31825adc81PMID:23292594
http://dx.doi.org/10.1097/BCR.0b013e3182... following their discharge and often have to be readmitted because of pre-existing comorbidities and ongoing chronic illness.⁸8 . Klein MB, Lezotte DC, Heltshe S, Fauerbach J, Holavanahalli RK, Rivara FP, et al. Functional and psychosocial outcomes of older adults after burn injury: results from a multicenter database of severe burn injury.. J Burn Care Res 2011 Jan-Feb;32(1):66-78. http://dx.doi.org/10.1097/BCR.0b013e318203336aPMID:21124232
http://dx.doi.org/10.1097/BCR.0b013e3182... ⁹9 . Lundgren RS, Kramer CB, Rivara FP, Wang J, Heimbach DM, Gibran NS, et al. Influence of comorbidities and age on outcome following burn injury in older adults.. J Burn Care Res 2009 Mar-Apr;30(2):307-14. http://dx.doi.org/10.1097/BCR.0b013e318198a416PMID:19165104
http://dx.doi.org/10.1097/BCR.0b013e3181... ¹²12 . Mandell SP, Pham T, Klein MB. Repeat hospitalization and mortality in older adult burn patients.. J Burn Care Res 2013 Jan-Feb;34(1):e36-41. http://dx.doi.org/10.1097/BCR.0b013e31825adc81PMID:23292594
http://dx.doi.org/10.1097/BCR.0b013e3182...

Using data on adults who have been hospitalized for burns in Western Australia, we investigate long-term mortality and the proportion of mortality attributable to the original burn injury.

Methods

Our study formed part of the Western Australian population-based burn injury project - a retrospective cohort investigation that uses administrative data from the Western Australian data linkage system. Administrative health data from several core data sets - including Western Australia's hospital morbidity data system and death register - are linked for the entire population of Western Australia.¹³13 . Holman CDJ, Bass AJ, Rouse IL, Hobbs MST. Population-based linkage of health records in Western Australia: development of a health services research linked database. Aust N Z J Public Health. 1999 Oct;23(5):453-9. http://dx.doi.org/10.1111/j.1467-842X.1999.tb01297.xPMID:10575763
http://dx.doi.org/10.1111/j.1467-842X.19... The project protocol was approved by the human research ethics committees of the University of Western Australia and the Western Australian department of health.

Staff at the Western Australian data linkage system provided a de-identified extraction of hospital morbidity records for all individuals who were aged at least 45 years when admitted to a hospital in Western Australia with a first burn injury between 1 January 1980 and 30 June 2012. Other than the unique identifying numbers assigned by staff at the Western Australian data linkage system, personal identifiers were removed from the data. We used the International Classification of Diseases and Related Health Problems (ICD9) CM 940-949 or (ICD10) AM T20-T31 codes to identify burn injuries. A first burn injury was defined as the first hospital admission in a patient's medical record in which a burn injury was given as the principal diagnosis or an additional diagnosis. A population-based comparison cohort was randomly selected from Western Australia's electoral roll. Any person with an injury hospitalization during the study period was excluded from this cohort by staff at the Western Australian data linkage system. The resultant comparison cohort was frequency matched on birth year and sex of each burn injury case - with four controls to each case - for each year from 1980 to 2012.

Data from Western Australia's hospital morbidity data system and death register were linked to the burn and non-injured cohorts for the period 1980-2012. Hospital admissions' data included principal and additional diagnoses, external cause of injury, age, sex, Aboriginal status, date of admission, date of discharge or other separation, mode of separation, percentage of total body surface area burned and burn depth. The data also included geocoded place of residence (census collectors' district or postcode), geocoded indices of geographical remoteness¹⁴14 . Glover J, Tennant S. Remote areas statistical geography in Australia: notes on the Accessibility/Remoteness Index for Australia (ARIA+ version). [Working Papers Series No. 9]. Adelaide: University of Adelaide; 2003. and social disadvantage.¹⁵15 . Trewin D. Socio-economic indexes for areas (Information Paper, Census of Population and Housing). Canberra: Australian Bureau of Statistics; 2003. Geographical remoteness was classified into five categories: major cities, inner regional, outer regional, remote and very remote. The social disadvantage index was reclassified into quintiles. The mortality data included date of death and cause of death, classified using ICD9-CM and ICD10-AM disease and external cause codes.

Individuals aged 45-54, 55-64 and at least 65 years were categorized as middle-aged, young-old and elderly, respectively. Individuals listed as Aboriginal or Torres Strait Islander on any admission record were categorized as Aboriginal. Supplementary codes ICD9-CM 948 or ICD10-AM T31, when available, were used to classify the patients into those with minor burns (less than 20% of total body surface area burned) and those with severe burns. Comorbidity was assessed, with a five-year look-back period, using the Charlson comorbidity index¹⁶16 . Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis. 1987;40(5):373-83. http://dx.doi.org/10.1016/0021-9681(87)90171-8PMID:3558716
http://dx.doi.org/10.1016/0021-9681(87)9... and the principal and additional diagnoses included in the hospital morbidity records.¹⁷17 . Preen DB, Holman CDAJ, Spilsbury K, Semmens JB, Brameld KJ. Length of comorbidity lookback period affected regression model performance of administrative health data. J Clin Epidemiol. 2006 Sep;59(9):940-6. http://dx.doi.org/10.1016/j.jclinepi.2005.12.013PMID:16895817
http://dx.doi.org/10.1016/j.jclinepi.200... The final discharge date for the burn patient was used as the starting point for the follow-up periods for both the burn injury and control cohort.

Categorical and non-parametric continuous variables were compared using χ2 and Kruskal-Wallis tests, respectively. A P-value of 0.05 or lower was considered statistically significant. Kaplan-Meier plots of survival estimates were generated and log rank tests were used to compare the survival distributions of the burn and non-injury cohorts. We compared burn versus non-injury and burn severity (minor burns, severe burns or burns with no record of the percentage of total body surface area affected) versus non-injury. Cox proportional hazard regression was used to estimate the effects of burn injury on long-term survival while adjusting for year of admission, age, sex, Aboriginal status, comorbidity score, social disadvantage, and geographical remoteness. The hazard ratios estimated from the Cox proportional hazards model were used as measures of mortality rate ratios. Preliminary analyses revealed no evidence of non-proportionality.¹⁸18 . Cleves M, Gutierrez R, Gould W, Marchenko Y. An introduction to survival analysis using Stata. 2nd ed. College Station: StataCorp LP; 2008. Attributable risk percentage - used to estimate the proportion of long-term mortality for which burn injury was an attributable cause - was calculated as 100 × (adjusted mortality rate ratio-1)/(adjusted mortality rate ratio).¹⁹19 . Gordis L. Epidemiology. 2nd ed. Philadelphia: WB Saunders; 2000.

The percentage of deaths in the burn cohort that were attributable to burn injury was estimated after adjusting for potential confounders. All statistical analyses were performed using Stata version 12 (StataCorp. LP, College Station, United States of America).

Results

During the study period, 6014 individuals aged 45 years or older were hospitalized in Western Australia for a first burn injury. Although 240 (4%) were recorded as having severe burns and 3248 (54%) as having minor burns, the percentage of the total body surface area affected by burns was not recorded for the remaining 2526 (42%). Overall, 1143 (19%) of patients had full-thickness burns, while 2225 (37%) had partial-thickness burns, 1082 (18%) had erythema and 1744 (29%) had burns of unspecified depth. Patients may have had multiple burns sites and depths recorded. In total, 4992 (83%) of patients were discharged to their home, 722 (12%) were transferred to acute care hospitals, 120 (2%) were transferred to facilities for elderly people and 180 (3%) died in hospital. Only 577 (10%) had additional non-burn injuries, most of which were open wounds or superficial injuries. Mortality among individuals with and without additional injury were similar (43% versus 41%; P= 0.356). Additional injuries in the burn cohort were therefore ignored in our subsequent analyses.

Our non-injury cohort comprised 25 759 individuals. Table 1 summarizes the baseline sociodemographic characteristics and comorbidity scores for both study cohorts. Compared with the non-injury cohort, the burn cohort had significantly higher proportions of Aboriginal people, people who were socially disadvantaged and people living outside major cities. The adults in the burn cohort were also significantly more likely to have pre-existing comorbidity than those in the non-injury cohort.

Over the study period, 2498 (42%) of the adults in the burn cohort and 7018 (27%) of those in the matched non-injury cohort died. Unadjusted Kaplan-Meier survival plots for the overall burn cohort versus the non-injury cohort (Fig. 1), and for the three separate categories for burn severity versus non-injury (Fig. 2), all showed higher survival estimates for those who had not suffered burns. Log rank tests - in which the unadjusted equality of survivorship between the non-injury cohort and the total burn cohort (P< 0.001) or each of the three categories for burn severity (P< 0.001) was assessed - all indicated that there were excess deaths in the burn cohort.

Compared with the adults in the non-injury cohort who died during the study period, the adults in the burn cohort who died were younger at the time of death - with a median age of 76 years (interquartile range: IQR: 67-85) versus 82 years (IQR: 73-88; P< 0.001).

Over the 33-year study period, the adults in the burn cohort were followed up for 0.01-32.5 years (median: 9; IQR: 3-16) to give a total of 59 882 person-years while those in the non-injury cohort were followed up for 0.01-32.5 years (median: 13; IQR: 6-23) to give a total of 488 443 person-years. Over the study period, the burn and non-injury cohorts had all-cause mortality rates of 419.4 and 143.7 deaths per 10 000 person-years, respectively - giving an unadjusted mortality rate ratio for burn injury of 2.9 (95% confidence interval, CI: 2.7-3.0). After adjustment for year of admission, age, sex, Aboriginal status, social disadvantage, remoteness and pre-existing comorbidity, the overall long-term adjusted mortality rate ratio for burn injury was 1.4 (95% CI: 1.3-1.5). Mortality attributable to burns was 29% (Table 2).

The all-cause mortality rate among females was 538.7 deaths per 10 000 person-years in the burn cohort and 253.1 deaths per 10 000 person-years in the non-injury cohort, giving an unadjusted mortality rate ratio for burn injury of 2.1 (95% CI: 2.0-2.3). The adjusted mortality rate ratio for females was 1.6 (95% CI: 1.5-1.7). Among males, the all-cause mortality rate in the burn cohort was also higher than that in the non-injury cohort - 359.9 versus 126.0 deaths per 10 000 person-years - giving an unadjusted mortality rate ratio of 2.8 (95% CI: 2.7-3.0). The adjusted mortality rate ratio for males was 1.3 (95% CI: 1.2-1.4).

The results of Cox regression models for subgroups of the burn cohort, classified by burn severity and age, are presented in Table 2. In these models, after adjustment for potential confounders, all of the subgroups of the burn cohort had a higher risk of death than the non-injury cohort. Individuals aged at least 65 years when they experienced the burn injury had a lower attributable risk (23%), than individuals aged 55-64 years (33%) and individuals aged 45-54 years (38%).

Discussion

Current estimates of the mortality related to burns have usually been based on deaths in hospital or within a few weeks of discharge.⁴4 . Pham TN, Kramer CB, Wang J, Rivara FP, Heimbach DM, Gibran NS, et al. Epidemiology and outcomes of older adults with burn injury: an analysis of the National Burn Repository. J Burn Care Res. 2009 Jan-Feb;30(1):30-6. http://dx.doi.org/10.1097/BCR.0b013e3181921efcPMID:19060727
http://dx.doi.org/10.1097/BCR.0b013e3181... ¹²12 . Mandell SP, Pham T, Klein MB. Repeat hospitalization and mortality in older adult burn patients.. J Burn Care Res 2013 Jan-Feb;34(1):e36-41. http://dx.doi.org/10.1097/BCR.0b013e31825adc81PMID:23292594
http://dx.doi.org/10.1097/BCR.0b013e3182... ²⁰20 . Brewster CT, Coyle B, Varma S. Trends in hospital admissions for burns in England, 1991-2010: a descriptive population-based study. Burns. 2013 Dec;39(8):1526-34. http://dx.doi.org/10.1016/j.burns.2013.09.019PMID:24210548
http://dx.doi.org/10.1016/j.burns.2013.0... ²³23 . Wasiak J, Spinks A, Ashby K, Clapperton A, Cleland H, Gabbe B. The epidemiology of burn injuries in an Australian setting, 2000-2006. Burns. 2009 Dec;35(8):1124-32. http://dx.doi.org/10.1016/j.burns.2009.04.016PMID:19482430
http://dx.doi.org/10.1016/j.burns.2009.0... In this study, however, follow-up lasted for a median of 9 years.

Up to the end of follow-up - and after adjusting for known potential confounders - our burn cohort was found to have 1.4-fold higher all-cause mortality than the non-injury cohort. The excess long-term mortality attributable to burn injury was 725 of the 2498 total deaths recorded in the burn cohort. These 725 deaths after discharge represent 12% of those hospitalized for burn injury while only 3% died in hospital after the index admission. These results, which indicate that the long-term mortality from burns is much higher than indicated by in-hospital mortality data, challenge the definition of fatal outcomes used in most assessments of burn injuries.

Compared with the non-injury cohort, the subgroups of the burn cohort with severe burns, minor burns or burns of unspecified severity each showed significantly increased risk of all-cause mortality during the study follow-up. We failed to demonstrate a positive relationship between burn severity and mortality because, within the burn cohort, we found the mortality to be highest for those with minor burns. Explanations for this phenomenon may be that people with the most severe burns died during the index hospital admission and/or the survivors of severe burns included in the analyses represented a relatively more robust patient population.

While burn injury principally affects the skin, it is associated with depression of humoral and cell-mediated immunity,²⁴24 . Jeschke MG, Barrow RE, Herndon DN. Extended hypermetabolic response of the liver in severely burned pediatric patients. Arch Surg. 2004 Jun;139(6):641-7. http://dx.doi.org/10.1001/archsurg.139.6.641PMID:15197091
http://dx.doi.org/10.1001/archsurg.139.6... ²⁵25 . Schmand JF, Ayala A, Chaudry IH. Effects of trauma, duration of hypotension, and resuscitation regimen on cellular immunity after hemorrhagic shock. Crit Care Med. 1994 Jul;22(7):1076-83. http://dx.doi.org/10.1097/00003246-199407000-00005PMID:8026194
http://dx.doi.org/10.1097/00003246-19940... sustained high levels of oxidative stress²⁶26 . Liu DM, Sun BW, Sun ZW, Jin Q, Sun Y, Chen X. Suppression of inflammatory cytokine production and oxidative stress by CO-releasing molecules-liberated CO in the small intestine of thermally-injured mice. Acta Pharmacol Sin. 2008 Jul;29(7):838-46. http://dx.doi.org/10.1111/j.1745-7254.2008.00816.xPMID:18565282
http://dx.doi.org/10.1111/j.1745-7254.20... and prolonged elevation of hypermetabolic and stress hormones.²⁷27 . Atiyeh BS, Gunn SWA, Dibo SA. Metabolic implications of severe burn injuries and their management: a systematic review of the literature. World J Surg. 2008 Aug;32(8):1857-69. http://dx.doi.org/10.1007/s00268-008-9587-8PMID:18454355
http://dx.doi.org/10.1007/s00268-008-958... ²⁸28 . Williams FN, Herndon DN, Jeschke MG. The hypermetabolic response to burn injury and interventions to modify this response. Clin Plast Surg. 2009 Oct;36(4):583-96. http://dx.doi.org/10.1016/j.cps.2009.05.001PMID:19793553
http://dx.doi.org/10.1016/j.cps.2009.05.... In children, metabolic and inflammatory changes have been found to last for at least three years after severe burns.²⁹29 . Jeschke MG, Gauglitz GG, Kulp GA, Finnerty CC, Williams FN, Kraft R, et al. Long-term persistance of the pathophysiologic response to severe burn injury. PLoS ONE. 2011;6(7):e21245. http://dx.doi.org/10.1371/journal.pone.0021245PMID:21789167
http://dx.doi.org/10.1371/journal.pone.0... Such changes have the potential to induce a range of health conditions including insulin resistance,³⁰30 . Gauglitz GG, Herndon DN, Kulp GA, Meyer WJ 3rd, Jeschke MG. Abnormal insulin sensitivity persists up to three years in pediatric patients post-burn. J Clin Endocrinol Metab. 2009 May;94(5):1656-64. http://dx.doi.org/10.1210/jc.2008-1947PMID:19240154
http://dx.doi.org/10.1210/jc.2008-1947... increases in the risk of fracture,³¹31 . Herndon DN, Tompkins RG. Support of the metabolic response to burn injury. Lancet. 2004 Jun 5;363(9424):1895-902. http://dx.doi.org/10.1016/S0140-6736(04)16360-5PMID:15183630
http://dx.doi.org/10.1016/S0140-6736(04)... sepsis and infections,²⁸28 . Williams FN, Herndon DN, Jeschke MG. The hypermetabolic response to burn injury and interventions to modify this response. Clin Plast Surg. 2009 Oct;36(4):583-96. http://dx.doi.org/10.1016/j.cps.2009.05.001PMID:19793553
http://dx.doi.org/10.1016/j.cps.2009.05.... ³²32 . Hart DW, Wolf SE, Mlcak R, Chinkes DL, Ramzy PI, Obeng MK, et al. Persistence of muscle catabolism after severe burn.. Surgery 2000 Aug;128(2):312-9. http://dx.doi.org/10.1067/msy.2000.108059PMID:10923010
http://dx.doi.org/10.1067/msy.2000.10805... enlargement of the liver,³³33 . Jeschke MG, Chinkes DL, Finnerty CC, Kulp G, Suman OE, Norbury WB, et al. Pathophysiologic response to severe burn injury. Ann Surg. 2008 Sep;248(3):387-401. PMID:18791359 ³⁴34 . Jeschke MG, Micak RP, Finnerty CC, Herndon DN. Changes in liver function and size after a severe thermal injury. Shock. 2007 Aug;28(2):172-7. http://dx.doi.org/10.1097/shk.0b013e318047b9e2PMID:17529902
http://dx.doi.org/10.1097/shk.0b013e3180... cardiac stress and dysfunction²⁸28 . Williams FN, Herndon DN, Jeschke MG. The hypermetabolic response to burn injury and interventions to modify this response. Clin Plast Surg. 2009 Oct;36(4):583-96. http://dx.doi.org/10.1016/j.cps.2009.05.001PMID:19793553
http://dx.doi.org/10.1016/j.cps.2009.05.... ³⁵35 . Williams FN, Herndon DN, Suman OE, Lee JO, Norbury WB, Branski LK, et al. Changes in cardiac physiology after severe burn injury.. J Burn Care Res 2011 Mar-Apr;32(2):269-74. http://dx.doi.org/10.1097/BCR.0b013e31820aafcfPMID:21228708
http://dx.doi.org/10.1097/BCR.0b013e3182... and hormonal abnormalities.³⁰30 . Gauglitz GG, Herndon DN, Kulp GA, Meyer WJ 3rd, Jeschke MG. Abnormal insulin sensitivity persists up to three years in pediatric patients post-burn. J Clin Endocrinol Metab. 2009 May;94(5):1656-64. http://dx.doi.org/10.1210/jc.2008-1947PMID:19240154
http://dx.doi.org/10.1210/jc.2008-1947... ³³33 . Jeschke MG, Chinkes DL, Finnerty CC, Kulp G, Suman OE, Norbury WB, et al. Pathophysiologic response to severe burn injury. Ann Surg. 2008 Sep;248(3):387-401. PMID:18791359 Recent research has also shown elevated cancer incidence after burn injury, particularly among female burn survivors.^36,37 Systemic responses are induced by both minor and moderate burns³⁸38 . Anderson JR, Zorbas JS, Phillips JK, Harrison JL, Dawson LF, Bolt SE, et al. Systemic decreases in cutaneous innervation after burn injury. J Invest Dermatol. 2010 Jul;130(7):1948-51. http://dx.doi.org/10.1038/jid.2010.47PMID:20336082
http://dx.doi.org/10.1038/jid.2010.47... ³⁹39 . Rea S, Giles NL, Webb S, Adcroft KF, Evill LM, Strickland DH, et al. Bone marrow-derived cells in the healing burn wound - more than just inflammation. Burns. 2009 May;35(3):356-64. http://dx.doi.org/10.1016/j.burns.2008.07.011PMID:18952376
http://dx.doi.org/10.1016/j.burns.2008.0... and may have contributed to the increased long-term mortality found, for both minor and severe burns, in this study. It has also been reported that patients who survive admission to an intensive care unit have poorer survival than the general population - perhaps indicating that any episode of critical illness or treatment for such illness can shorten life expectancy.⁴⁰40 . Williams TA, Dobb GJ, Finn JC, Knuiman MW, Geelhoed E, Lee KY, et al. Determinants of long-term survival after intensive care.. Crit Care Med 2008 May;36(5):1523-30. http://dx.doi.org/10.1097/CCM.0b013e318170a405PMID:18434893
http://dx.doi.org/10.1097/CCM.0b013e3181...

Our analysis by age group indicated that the mortality rate ratios - and consequent attributable risk percentages - for burn injury decreased slightly with increasing age. Although the proportion of deaths attributable to burn injury was smaller for the elderly individuals than the middle-aged or young-old individuals, the absolute number of deaths was greatest among the elderly individuals.

Some of the consequences of burn injury appear to be experienced long after the initial period of recovery. Minor burns in elderly people tend to lead to longer hospital stays and higher in-hospital mortality when compared with younger adults.⁴4 . Pham TN, Kramer CB, Wang J, Rivara FP, Heimbach DM, Gibran NS, et al. Epidemiology and outcomes of older adults with burn injury: an analysis of the National Burn Repository. J Burn Care Res. 2009 Jan-Feb;30(1):30-6. http://dx.doi.org/10.1097/BCR.0b013e3181921efcPMID:19060727
http://dx.doi.org/10.1097/BCR.0b013e3181... ²¹21 . Duke J, Wood F, Semmens J, Spilsbury K, Edgar DW, Hendrie D, et al. A 26-year population-based study of burn injury hospital admissions in Western Australia.. J Burn Care Res 2011 May-Jun;32(3):379-86. http://dx.doi.org/10.1097/BCR.0b013e318219d16cPMID:21448072
http://dx.doi.org/10.1097/BCR.0b013e3182... ⁴¹41 . Callaway DW, Wolfe R. Geriatric trauma. Emerg Med Clin North Am. 2007 Aug;25(3):837-60, x. http://dx.doi.org/10.1016/j.emc.2007.06.005PMID:17826220
http://dx.doi.org/10.1016/j.emc.2007.06.... Among elderly people, burn injuries may worsen pre-existing health conditions, hamper good nutrition, reduce mobility and independence⁹9 . Lundgren RS, Kramer CB, Rivara FP, Wang J, Heimbach DM, Gibran NS, et al. Influence of comorbidities and age on outcome following burn injury in older adults.. J Burn Care Res 2009 Mar-Apr;30(2):307-14. http://dx.doi.org/10.1097/BCR.0b013e318198a416PMID:19165104
http://dx.doi.org/10.1097/BCR.0b013e3181... ⁴²42 . Campbell JW, Degolia PA, Fallon WF, Rader EL. In harm's way: moving the older trauma patient toward a better outcome. Geriatrics. 2009 Jan;64(1):8-13. PMID:19256576 and prevent them from regaining their previous state of health.¹²12 . Mandell SP, Pham T, Klein MB. Repeat hospitalization and mortality in older adult burn patients.. J Burn Care Res 2013 Jan-Feb;34(1):e36-41. http://dx.doi.org/10.1097/BCR.0b013e31825adc81PMID:23292594
http://dx.doi.org/10.1097/BCR.0b013e3182... An ageing population is characterized by an increasing prevalence of frailty.⁴³43 . Clegg A, Young J, Iliffe S, Rikkert MO, Rockwood K. Frailty in elderly people. Lancet. 2013 Mar 2;381(9868):752-62. http://dx.doi.org/10.1016/S0140-6736(12)62167-9PMID:23395245
http://dx.doi.org/10.1016/S0140-6736(12)...

The strengths of our study are the inclusion of a non-injured comparison group and a follow-up period designed to reveal the long-term mortality risk associated with burns among older adults. Previous single-centre studies have lacked a control group⁴⁴44 . Sheridan RL, Hinson MI, Liang MH, Nackel AF, Schoenfeld DA, Ryan CM, et al. Long-term outcome of children surviving massive burns. JAMA. 2000 Jan 5;283(1):69-73. http://dx.doi.org/10.1001/jama.283.1.69PMID:10632282
http://dx.doi.org/10.1001/jama.283.1.69... or followed patients for no more than two to three years.¹²12 . Mandell SP, Pham T, Klein MB. Repeat hospitalization and mortality in older adult burn patients.. J Burn Care Res 2013 Jan-Feb;34(1):e36-41. http://dx.doi.org/10.1097/BCR.0b013e31825adc81PMID:23292594
http://dx.doi.org/10.1097/BCR.0b013e3182... ²⁹29 . Jeschke MG, Gauglitz GG, Kulp GA, Finnerty CC, Williams FN, Kraft R, et al. Long-term persistance of the pathophysiologic response to severe burn injury. PLoS ONE. 2011;6(7):e21245. http://dx.doi.org/10.1371/journal.pone.0021245PMID:21789167
http://dx.doi.org/10.1371/journal.pone.0... Long-term mortality of injury has been investigated previously, but with few burn cases.⁴⁵45 . Cameron CM, Purdie DM, Kliewer EV, McClure RJ. Long-term mortality following trauma: 10 year follow-up in a population-based sample of injured adults. J Trauma. 2005 Sep;59(3):639-46. PMID:16361907 We assumed that, after adjustment for confounding, the excess in mortality in the burn cohort was predominantly associated with burn injuries.¹⁹19 . Gordis L. Epidemiology. 2nd ed. Philadelphia: WB Saunders; 2000. Our use of linked health administrative data enabled both the identification of a cohort of adults hospitalized for a first burn injury and the estimation of the pre-existing comorbidities in that cohort. We included indices of social disadvantage, geographical remoteness and access to services.

As a consequence of incomplete data for the percentage of the total body surface area affected for many people with burn injury, we were unable to show the effects of burn severity on long-term mortality. A non-injured control cohort was used to examine the potential systemic health impacts of trauma caused specifically by burn injury sufficiently serious to require hospitalization. Future research will examine potential differences between burn and non-burn injury and long-term health impacts.

The fact that the Western Australia hospital morbidity data system is assessed continually for both quality and accuracy strengthens our findings.⁴⁶46 . Clinical information audit program - hospital activity report. Perth: Department of Health, Western Australia; 2009. Our main finding is expected to be generalizable to other populations with similar demographic characteristics and comparable health-care systems to those of Australia.

In conclusion, our findings that the long-term all-cause mortality was increased in the burn injury cohort suggest that any estimate of the mortality burden from burn injury based on in-hospital deaths alone will underestimate the true burden. These findings have implications for the clinical management of burn injury and should encourage the development of programmes for both long-term support for people with burn injury and the prevention of such injury.

Acknowledgements

The authors thank the staff of the health information linkage branch for access to the Western Australian data linkage system, the Western Australian health data custodians and the Western Australian department of health.

References

Publication Dates

History