Article Text

Download PDFPDF

Autism spectrum disorder and unintentional fatal drowning of children and adolescents in Australia: an epidemiological analysis
  1. Amy E Peden1,2,3,
  2. Stacey Willcox-Pidgeon1,3
  1. 1 Royal Life Saving Society - Australia, Broadway, New South Wales, Australia
  2. 2 School of Public Health and Community Medicine, University of New South Wales Faculty of Medicine, Kensington, New South Wales, Australia
  3. 3 College of Public Health, Medical and Veterinary Sciences, Discipline of Public Health and Tropical Medicine, James Cook University, Townsville, Queensland, Australia
  1. Correspondence to Dr Amy E Peden, School of Public Health and Community Medicine, University of New South Wales, Kensington, NSW 2052, Australia; a.peden{at}unsw.edu.au

Abstract

Objectives This study explored unintentional fatal drowning among children and adolescents (0–19 years) diagnosed with autism spectrum disorder (ASD) in Australia.

Design This total population, cross-sectional audit used data from the Royal Life Saving National Fatal Drowning Database to explore demographic and causal factors in ASD drowning cases between 1 July 2002 and 30 June 2018. Rates and relative risk (RR) with a 95% confidence interval (CI) were calculated for drowning cases with and without ASD, using estimated population-level prevalence data.

Results Of the 667 cases of drowning among 0–19 year olds with known medical history, 27 children and adolescents (4.0%) who drowned had an ASD diagnosis. Children and adolescents with ASD were three times more likely to drown than those without ASD (RR=2.85; CI 0.61 to 13.24). Among those with ASD, 0–4 year olds record the highest rate (11.60/100 000 diagnosed). Children and adolescents with ASD were significantly more likely to drown when compared with those without ASD: if aged 5–9 years (44.4% of ASD-yes cases; 13.3% of ASD-no cases); in a lake or dam (25.9% vs 10.0%) and during winter (37.0% vs 13.1%).

Conclusion Heightened awareness of drowning risk for children and adolescents with ASD is required, including adult supervision and barriers restricting water access. Further evaluation of the effectiveness of personal alarms to alert caregivers to an unsupervised child is warranted. Challenges exist regarding accurate estimates of population-level ASD prevalence and identification of ASD in coronial files. As the diagnosis of ASD does not often occur until age five, results may be an underestimate.

  • autism
  • accident & emergency
  • epidemiology
  • injury prevention
  • mortality

Statistics from Altmetric.com

What is already known on this topic?

  • Children under five are the age group at highest risk of drowning.

  • Studies from other countries indicate increased drowning risk for children with autism spectrum disorder (ASD).

  • There has been no prior total population analysis of drowning among children and adolescents with ASD in Australia.

What this study adds?

  • Children and adolescents (0–19 years) with ASD drown at a rate three times that of children and adolescents without ASD (relative risk=2.85; CI 0.61 to 13.24).

  • The highest rates were in children 0–4 years (11.60/100 000 children diagnosed), although diagnosis commonly occurs around age 5.

  • When compared with children and adolescents without ASD, those with ASD were significantly more likely to drown if aged 5–9 years old, in lakes/dams and during winter.

Introduction

The global fatal drowning burden is estimated at 360 000 lives annually.1 This estimate, however, under-reports drowning in high-income countries by 40%–50% by excluding water transportation and disaster-related deaths.2 3 Over half of all drowning deaths globally occur in children and young people 25 years and younger, with children 0–4 years at highest risk1 due to an absence of supervision,4 unrestricted access to water5 and limited swimming ability.6

In Australia, 279 people on average unintentionally fatally drown each year,7 representing an economic burden of $1.24 billion (2017 dollars) annually.8 Children under five record the highest rates of both fatal drowning and non-fatal drowning requiring hospitalisation.9 Conversely, drowning rates are low among 5–14 year olds in Australia, partly from reduced exposure due to formal schooling;10 however, drowning rates increase again in late adolescence.11

Pre-existing medical conditions are a factor increasing drowning risk.12–16 While seizure disorders such as epilepsy have been specifically identified,12 17 recent literature has focused on autism spectrum disorder (ASD) and the increased risk of child injury,18 including drowning.19 Comorbidities such as intellectual disabilities, epilepsy, mental health and chronic physical health conditions are also associated with increased risk of death among those with ASD.20

According to the ‘Diagnostic and statistical manual of mental disorders’ (5th edition) or DSM-5, a diagnosis of ASD is characterised by difficulties in social communication and restricted, repetitive behaviour or interests.21 A key shift between DSM-4 and DSM-5 (released in 2013) occurred in the diagnosis of ASD. There is now a single diagnosis which replaces the previous different subdivisions: autistic disorder; Asperger’s disorder and pervasive developmental disorder—not otherwise specified.21

In recent years, ASD diagnosis in Australia has increased, with the Australian Bureau of Statistics (ABS) reporting all age prevalence of 64 600 people in 200922 compared with 164 000 in 201523 (the most current estimates available at time of writing). Similarly, the USA reports a similar increase in incidence over the last two decades from 1 in 150 children, to 1 in 68 children.19

International research indicates people with ASD experience up to a 10-fold increased risk of premature death compared with the general population.18 Children with ASD are at heightened risk of unintentional injury, particularly drowning 19. Given recent attention to the issue of ASD and drowning risk among children internationally, and minimal population-level research on the issue, including in Australia, this study aimed to explore the frequency and circumstances of drowning among children and adolescents aged 0–19 years with ASD, including risk differences based on age, to inform prevention efforts.

Methods

All unintentional fatal drowning cases (regardless of International Classification of Diseases (ICD-10) code) are captured in the Royal Life Saving National Fatal Drowning Database (the Database).24 Cases in the Database are sourced using data triangulation, a method published previously.3 25 In brief, fatal drowning is considered a sudden and unexpected death in Australia and therefore must be investigated by a coroner. This investigation includes police, autopsy and toxicology reports which a coroner uses to finalise a coroners’ report which confirms cause and circumstances of death.

All such cases are entered onto the National Coronial Information System (NCIS), an online repository of such documentation. Cases on the NCIS are open while under coronial investigation and feature little information. Once closed (ie, a coroner has made a ruling as to cause and circumstances of death), case details are finalised and documentation attached. Cases in the Database are sourced primarily from the NCIS, as well as drowning reports from media,26 police, child death review and lifesaving organisations. All non-NCIS cases were cross-referenced against the NCIS. Open cases are entered into the Database and regularly updated against the NCIS until such time as the case is closed at which point the case record on the NCIS, and therefore in the Database, is unlikely to change.

Database cases of drowning for those aged 0–19 years between 1 July 2002 and 30 June 2018 (the Australian financial year) were screened for the terms ‘autism’, ‘autism spectrum disorder’, ‘Asperger’s syndrome’ in the cause of death and medical conditions fields. The full text police, autopsy and coroners reports were also reviewed for all causes to ensure no ASD-yes cases in the database had been missed. Screening was conducted manually by researchers reading through case files on the NCIS and transferring relevant information into the Database record for the child. At the time of initial entry into the Database (in the financial year within which the drowning occurred), any relevant details with respect to medical history and causal factors (such as ASD) are included. Cases in the Database are then validated (generally in the following financial year) against the closed file for the case on the NCIS; meaning details of the case are confirmed and will not change. Author SW-P initially screened all fatal drowning cases in the Database among children 0–19 years for ASD, with author AEP double screening those cases marked as ASD-yes including ensuring an ASD diagnosis was confirmed.

Only those with a confirmed diagnosis of ASD were coded as ASD-yes. For the purposes of this study, a confirmed diagnosis was defined as either (1) ASD being listed as a contributory cause of death by the coroner; (2) a statement in the coroner’s report regarding involvement of ASD and/or (3) a parent/caregiver witness statement in the police report regarding a diagnosis of ASD (ie, ‘The deceased suffered from autism and was unable to communicate verbally’). Cases of suspected autism were not included (n=2) (ie, ‘Parents suspected child of having autism but had not had this medically confirmed’). Closed cases without an ASD diagnosis were coded as ASD-no, with open cases coded as ASD-unknown, due to the lack of documentation regarding the drowning incident and the child’s pre-existing conditions. Closed coronial cases with no medical history were also coded as ASD-unknown. A total of 877 children and adolescents aged 0–19 years died from unintentional drowning during the study period. Of the 877 deaths, medical history information was known in 667 cases (76.1%). Only ASD-yes and ASD-no cases were used in this analysis.

Variables analysed included sex, age group, location of drowning incident, activity being undertaken immediately prior to drowning. Data from the NCIS for variables such as location and activity were categorised and coded from case file documentation as per the Royal Life Saving National Fatal Drowning Data Dictionary and Coding Manual.24 Due to the diversity of activities being undertaken prior to drowning, those activity types with less than five cases were grouped into the ‘Other’ category. Seasons in Australia are as follows: Summer (December to February); Autumn (March to May); Winter (June to August); Spring (September to November).

χ² analysis was undertaken to determine differences in the demographics and circumstances of drowning of children and adolescents with and without ASD. For variables with small counts (ie, 5 and under), a Fishers exact test was used.

Crude drowning rates per 100 000 population and relative risk (RR) with a 95% CI were calculated for those with and without ASD. RR was also calculated within the age groups of those who drowned with ASD (eg, 0–4, 5–9, 10–14 and 15–19 years). Rates for those with ASD were calculated using data on the estimated population-level prevalence of ASD from the ABS. The number of those aged 0–19 years in Australia with ASD for 200922 and 201523 was used. Data on ASD prevalence in both 2009 and 2015 were calculated using data derived from the 2009 and 2015 Survey of Disability, Ageing and Carers (SDAC) which collected data from household personal interviews as well as small questionnaires sent to a sample of residential care facilities.22 23

There were two time points for ASD population-level prevalence and the 16 years of fatal drowning data available. Therefore, annual means for the prevalence and drowning deaths data (ie, a 2-year average of the prevalence data and a 16-year average for the deaths) were used to calculate rates. The number of those with ASD was subtracted from the total population of each age group in 2009 and 201527 to calculate the number of children and adolescents without ASD. The age group with the lowest rate was the reference group for calculating RR.

Results

Of the 667 cases with known medical history, 27 (4.0%) children and adolescents were known to have ASD. Males accounted for 81.5% of all drowning cases of those with ASD, although sex was not statistically significant. The mean age of those who drowned with ASD was 7.5 years (SD=4.65). Children aged 5–9 years with ASD were more likely to drown than those without ASD (χ²=20.2; p<0.001), accounting for 44.4% of all who drowned with ASD, compared with 13.3% of all ASD-no cases (table 1).

Table 1

Demographics and drowning circumstance variables of child and adolescent (0–19 years) drowning deaths, with and without ASD, χ² (p value), Australia, 2002/2003–2017/2018

Children and adolescents with ASD were more likely to drown in a lake/dam when compared with those without (χ²=6.9; p=0.009; 25.9% of ASD-yes cases vs 10.0% of ASD-no cases). Falls into water were the leading activity being undertaken prior to drowning among those with ASD, accounting for 55.6% of deaths. There was no statistically significant difference in activity prior to drowning for children and adolescents with ASD when compared with those without. Summer and winter were the two leading seasons for drowning incidents among children and adolescents with ASD (37.0%, respectively). When compared with children and adolescents without ASD, those with ASD were more likely to drown in winter (χ²=12.2; p<0.001; 37.0% of ASD-yes cases vs 13.1% of ASD-no cases) (table 1).

Children and adolescents aged 0–19 years with ASD record a drowning rate of 2.02 per 100 000 diagnosed, a RR three times (RR=2.85; CI 0.61 to 13.24) that of children and adolescents in the same age group without ASD. When comparing those with ASD to those without by age group, the 0–4 years age group record the highest drowning rate, with children 0–4 years with ASD drowning at a rate of 11.60 per 100 000 diagnosed, a RR eight times (RR=7.64; CI 0.59 to 99.11) that of 0–4 year olds without ASD. The risk is lowest among those aged 10–14 years, with those aged 10–14 years with ASD recording a drowning rate of 0.43 per 100 000 diagnosed, before increasing again in the 15–19 years age group, with a drowning rate of 1.32 per 100 000 diagnosed (table 2).

Table 2

RR with 95% CI comparing children and adolescents with and without ASD 0–19 years and by age group, Australia, 2002/2003 and 2017/2018

When examining drowning rates and RR by age group among those with ASD, children 0–4 years drown at a rate that is 36 times (RR=36.24; CI 0.04 to 29 285.67) that of the control group (10–14 year olds). The risk is next highest among 5–9 year olds, drowning at a rate eight times (RR=7.65; CI 0.01 to 5477.45) that of 10–14 year olds with ASD.

Discussion

Pre-existing medical conditions increase drowning risk,12–16 with seizure disorders12 17 and cardiac conditions15 16 commonly identified. This study aimed to explore the impact of ASD on drowning risk among children and adolescents in Australia while also exploring causal factors to better inform prevention efforts. Findings show that children and adolescents with ASD drown at a rate that is three times that of children and adolescents without ASD (RR=2.85; CI 0.61 to 13.24). While the highest rates among those who drown with ASD occur among 0–4 year olds (11.60/100 000 diagnosed), when compared with those without ASD, children aged 5–9 years were significantly more likely to drown (χ²=20.2; p<0.001; 44% of ASD-yes cases vs 13% of ASD-no cases).

Key risk factors were also identified, which may differ to common perceptions of drowning risk in Australia. Although 0–4 year olds are the age group at highest risk of drowning,11 28 5–9 year olds with ASD are also at risk, being significantly more likely to drown than those in the same age group without ASD. While swimming pools4 5 and bathtubs29 30 are well-understood as locations posing a drowning risk to children, inland waterways, in particular lakes/dams, pose a significantly higher risk of drowning for both children and adolescents with ASD (χ²=6.9; p=0.009; 26% of ASD-yes cases vs 10% of ASD-no cases). And, although the largest proportion of fatal drownings occur during the summer months in Australia,26 children and adolescents with ASD are significantly more likely to drown during winter (χ²=12.2; p<0.001; 37% of ASD-yes cases vs 13% of ASD-no cases).

Given the above risk factors differ somewhat from the ‘traditional’ child and adolescent drowning prevention messages, there is a role for both drowning prevention advocates and ASD-related organisations in highlighting the unique drowning risk factors for children and adolescents with ASD as well as communicate prevention strategies. Well-established prevention strategies such as pool fencing31 and active adult supervision32 are relevant to children and adolescents with ASD. Due to the risk presented by natural waterways such as rivers, lakes and dams, child safe play areas are often proposed. A child safe play area is where a child is fenced into a safe area and is commonly used on farms and rural properties where natural water hazards such as dams and rivers cannot be fenced.33 Such a strategy may be a suitable for children and adolescents with ASD who reside in an area where natural waterways are accessible when wandering. As children grow older, parental or caregiver supervision and restricting access to water may become more challenging. Advances in technology and their integration into drowning prevention efforts may be beneficial. Global positioning systems19 and personal alarms to alert parents and caregivers when a child or adolescent with ASD has wandered away from adult supervision have been proposed to reduce injury risk;34 however, further evaluation of their effectiveness as a drowning prevention strategy is required. Swimming and water safety lessons with a focus on survival skills, if undertaken with appropriate instruction, has also been proposed as a drowning prevention strategy potentially suitable for children and adolescents with ASD.18 35

There is little literature exploring drowning risk among children and adolescents with ASD, and no studies using total population data. Guan and Li’s study of fatal unintentional drowning incidents among children with ASD under 15 years of age in the USA used newspaper reports to identify incidents and record demographic and causal factors.19 Similar to the findings of the current study, Guan and Li19 found a high proportion of males drowning (78% compared with 81% in the current study); those who drowned with ASD had a mean age of 7.7 years (compared with 7.5 years in the current study) and commonly drowned in natural water bodies such as ponds (52%), rivers (13%) and lakes (13%) (rivers, creeks and streams 22%; lakes/dams 26% in the current study). While swimming pools accounted for 26% of fatal drownings among children and adolescents with ASD in the current study, they accounted for just 9% of deaths in the Guan and Li study.19

Data availability presented a challenge when developing this study. Coronial data attached to cases of child and adolescent drowning often did not report on the presence of pre-existing medical conditions (24% unknown). Similarly, there was confusion in several cases as to whether a formal diagnosis of ASD had been made in children and adolescents who drowned with suspected ASD. It is therefore recommended that information on potential contributory medical conditions, such as ASD should be routinely sourced through witness reports and recorded in police summaries of the circumstances.

Similarly, there were challenges posed by the varying estimates of the prevalence of ASD among the general child and adolescent population in Australia. Recent studies cite estimates from Autism Spectrum Australia of a prevalence of ASD among the general Australian population of 1.4%36 and a parent-reported prevalence of ASD of 1.5%–2.5% for children recruited at birth and kindergarten, respectively.37 The current study used ABS data from 2009 and 2015 with an increase in almost 100 000 cases between data time points. More accurate population-level data on the prevalence of ASD by age group would assist in refining RR calculations. Though children aged 0–4 years with ASD recorded the highest rate of drowning, this is likely skewed due to children most commonly being definitively diagnosed from age five.20

Strengths and limitations

This is a total population study of all fatal unintentional drownings in Australia. The study is longitudinal in nature, examining data from a 16 financial year period. Data are drawn from the coronial system, meaning rich detail is available on causal factors leading to drowning, with which to inform prevention efforts. However, this study is not without its limitations. Information on pre-existing medical condition was unknown in 23.9% of cases; therefore, this study may underreport the total number of drowning deaths during the study period among children and adolescents with ASD. Similarly, if information about ASD was not reported in the case documentation, the authors were not able to identify the case as an ASD-related drowning. In two cases, those who drowned with suspected autism, but without a diagnosis, were not included in the cases of diagnosed ASD for this study. Similarly, while population-level data on the prevalence of ASD were sourced from the ABS, other organisations quote higher numbers on the prevalence of ASD among the Australian population (although without age breakdowns). Use of different denominator data would result in different rates and RR calculations than those shown in this study. While large increases were seen in the prevalence estimates of ASD between 2009 and 2015 due to improvements in screening and diagnosis, the same comprehensive method for screening drowning deaths data for ASD was applied throughout the 16 years of data included in this study. Methods used in the SDAC to derive population prevalence of ASD may under estimate the overall prevalence of ASD in Australia.

Conclusion

Children with ASD had higher reported rates of drowning if aged 5–9 years old, in lakes/dams and during the winter months. Over half of all ASD-related drownings occurred due to falls into water. Parents and caregivers of children with diagnosed ASD or with suspected ASD should be counselled on the increased risk of drowning and strategies to reduce this risk. Such strategies include active adult supervision and barriers restricting access to water such as four-sided isolation pool fencing and child safe play areas in locations where the risk of drowning is posed by natural waterways. The effectiveness of personal alarms as a drowning prevention strategy for children and adolescents with ASD requires further testing. Future research into the topic will benefit from improved data, both the recording of ASD among coronial files for those who drown and more accurate population-level prevalence estimates.

References

Footnotes

  • Twitter @amyepeden

  • Contributors AEP and SWP conceived the study. AEP and SWP collated the drowning data. SWP screened cases for ASD, with secondary validation by AEP. AEP conducted the analysis and drafted the manuscript. SWP critically reviewed the manuscript. Both authors approve the final version of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval Ethical approval was granted by the Victorian Department of Justice Human Research Ethics Committee (JHREC) (CF/07/13729; CF/10/25057, CF/13/19798).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are not publicly available but may be obtained from a third party. This study contains coronial data used under strict ethical approval from the National Coronial Information System (NCIS). Due to ethical constraints the underlying dataset cannot be uploaded. Those interested in gaining access to Australia coronial data may contact the NCIS for more information on ncis@ncis.org.au.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Linked Articles

  • Atoms
    Nick Brown