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Childhood injuries
Drowning and near-drowning in Northern Territory children
Karen M Edmond, John R Attia, Catherine A D'Este and John T Condon
MJA 2001; 175: 605-608
For editorial comment, see Pitt and Cass
Abstract -
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Objective: To compare incidences of drowing for
children in the Northern Territory (NT) with those in Queensland and
the rest of Australia.
Design: Descriptive, retrospective,
population-based analysis of death and hospitalisation data for
drowning and near-drowning.
Setting and participants: Children aged 0-14 years
resident in Australia from 1983 to 1998.
Main outcome measures: Age-standardised average
annual incidence of drowning (1983-1998) and near-drowning
(1994-1997) in children aged 0-4 and 5-14 years in the NT, Queensland
and the rest of Australia.
Results: The average annual incidence of drowning
and near-drowning from 1994 to 1997 for children aged 0-4 years in the
NT (67.82 per 100 000) was significantly higher than for Australia
(24.45 per 100 000) (incident rate ratio [IRR], 2.77; 95% CI,
1.40-4.91) and for Queensland (32.55 per 100 000) (IRR, 2.13; 95% CI,
1.05-3.94). The proportion of children aged 0-4 years drowning or
near-drowning in swimming pools from 1994 to 1997 was also
significantly higher in the NT (83%) than Australia (64%)
(difference, 0.19; 95% CI, 0.086-0.30) and Queensland (65%)
(difference, 0.18; 95% CI, 0.069-0.29). From 1983 to 1998, the
incidence of drowning in NT children aged 0-4 years increased by 0.4%
per year (IRR, 1.004; 95% CI, 0.994-1.070), compared with a 5.0%
reduction per year (IRR, 0.950; 95% CI, 0.937-0.963) in Australian
children.
Conclusions: The incidences of drowning and
near-drowning in the NT are higher than in the rest of Australia and
show no significant decrease. The NT should improve its measures for
prevention of childhood drowning.
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In Australia, childhood drownings are second only to road trauma as a
cause of injury death in children younger than 15 years.1,2
Encouragingly, the overall incidence of
childhood drowning in Australia appears to be
decreasing.1,3
However, drowning death rates are higher in the
Northern Territory (NT) than the rest of Australia.1,4-6 There is
also some evidence that rates of drowning in the NT are not decreasing
as fast as those in the rest of Australia.4,5 However, there are no
published studies that compare rates of near-drowning in the NT with
rates in the rest of Australia. There are also no published analyses of
NT drowning trends.
Risk groups for drowning include children aged 0-4 years,1,3 children
living in cities with high swimming pool to population
ratios,7-10 children living in hot
climates,3,8
children living in areas with lack of isolation
pool fencing,11-14 and Indigenous
children.4,5,7
However, there are no published NT data
concerning these risk groups. The proportion of NT children drowning
in swimming pools is also currently unknown.
This study was designed to determine how incidences of childhood
drowning and near-drowning in the NT compare with rates in the rest of
Australia and in Queensland (another State with a similar climate and
similar numbers of domestic swimming pools per capita as the NT). We
aimed to stratify our analysis according to specific risk groups
(children aged 0-4 years, children aged 5-14 years, children
drowning in swimming pools, and Indigenous children). We also
planned to compare the proportion of NT children aged 0-4 years who
drowned or nearly drowned in swimming pools with Queensland and the
rest of Australia. The study was designed as a descriptive,
retrospective, population-based analysis of hospital morbidity
and mortality data for drowning and near-drowning, identified by
International classification of diseases, 9th revision,
clinical modification (ICD-9-CM) codes15 in children aged 0-14
years.
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Definitions |
A drowning incident was defined as a non-intentional episode in which
immersion of a child in water was followed by death. A near-drowning
incident was defined as a non-intentional episode in which immersion
of a child in water was followed by admission into hospital and the
child subsequently surviving. A case was only included as a drowning
or near-drowning if it was identified by specific ICD-9-CM external
(E) cause codes (830, 832, 919.0-910.9) or the ICD-9-CM disease code
for near-drowning (994.1).15 E-codes classify
environmental sites, events, circumstances, and conditions as the
cause of injury, and include a code for swimming pool
drowning.15
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Data collection | |
Mortality and hospital morbidity data for all cases of drowning and
near-drowning were obtained from the Australian Institute of Health
and Welfare (AIHW). Mortality data were available for 1983-1998, but
hospital morbidity near-drowning data were available for 1994-1997
only, because of the introduction of casemix funding and changes in
ICD-9-CM coding.16 Population denominators
for the NT, Queensland and the rest of Australia were the estimated
resident population data for each year published by the Australian
Bureau of Statistics (ABS).17 NT Indigenous population
data were the estimates of the NT Indigenous population published by
the ABS.18
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Data analysis |
Crude incidences of drowning and near-drowning for the NT,
Queensland and the rest of Australia were standardised year by year
within 0-4 and 5-14 years age groups using the indirect
standardisation method and the Australian population as the
reference population.19
The annual number of cases was assumed to follow a Poisson
distribution.20 Changes in annual
drowning death rates from 1983 to 1998 were investigated using the
Mantel test for trend and a Poisson regression model which included
terms for year. NT average annual incidences of age-standardised
drowning and near-drowning were compared with Queensland and the
rest of Australia using incident rate ratios (IRR) and 95% confidence
intervals. An IRR was defined as the ratio of two incidences. The
difference between proportions of children drowning or nearly
drowning in swimming pools in the NT, Queensland and the rest of
Australia was compared using tests of difference between two
proportions and 95% confidence intervals. Stata software was used
for statistical analysis.21
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Ethical approval | |
This study was approved by the Joint Institutional Ethics Committee
of the Royal Darwin Hospital and the Menzies School of Health
Research.
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Drowning |
Forty-two NT children drowned from 1983 to 1998. There was no
significant change in the incidence of drowning over this period in NT
children aged 0-4 or 5-14 years (Boxes 1 and 2). In contrast, rates of
drowning in Australian children reduced significantly each year in
children aged 0-4 years (Boxes 1A and 2). Rates in Australian children
aged 5-14 years also reduced each year, but the Poisson regression
rate ratio for trend per year did not reach statistical significance
(Boxes 1B and 2). The average annual incidence of drowning in NT,
Australian and Queensland children from 1994 to 1997 is shown in Box 3.
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Near-drowning | |
The NT incidence of near-drowning for children aged 0-4 years was
higher than the Queensland rate, but not statistically significant,
while the rate for children aged 5-14 years was similar to the
Queensland rate (Box 3).
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Swimming pool drowning and near-drowning | |
The proportion of children aged 0-4 years drowning or near-drowning
in swimming pools from 1994 to 1997 in the NT (83%) was higher than in
Queensland (65%) (difference, 0.18; 95% CI, 0.069-0.29) and the rest
of Australia (64%) (difference, 0.19; 95% CI, 0.086-0.30) (see Box 3
for incidence).
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Indigenous status | |
In the NT, non-Indigenous children aged 0-4 years had higher rates of
drowning and near-drowning (73.19 per 100 000) than Indigenous
children (56.63 per 100 000) (IRR, 1.29; 95% CI, 0.53-4.47), although
this was not significant. Non-Indigenous children aged 5-14 years
also had higher rates of drowning and near-drowning (7.27 per 100 000)
than Indigenous children (5.41 per 100 000; IRR, 1.34; 95% CI,
0.81-5.42).
Rates of swimming pool drowning in the NT were also higher in
non-Indigenous children aged 0-4 years (24.89 per 100 000) than
Indigenous children (14.04 per 100 000) but this difference was not
significant (IRR, 1.77; 95% CI, 0.91-6.22). Only five of 40 children
(13%) aged 0-4 years who drowned in a swimming pool in the NT from 1983 to
1998 were Indigenous.
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This study describes the extremely high incidence of drowning and
near-drowning in children in the NT. Incidences were higher than in
the rest of Australia and showed no significant decrease despite
reductions in the rest of Australia. Rates in the NT are among the
highest recorded worldwide.3-5
Indigenous children in the NT had lower rates of drowning and
near-drowning than non-Indigenous children, as well as lower rates
of swimming pool drowning, although the differences were not
statistically significant. Case numbers of fresh water drownings
were too small to allow statistical analysis. Some studies describe
rates of drowning and near-drowning in Native American children to be
two to three times those of non-Native American children.7,10 However,
Australian studies report rates of Indigenous child drowning
mortality similar to those reported here.4,5 Reporting of Indigenous
status in the NT is accurate, in contrast to other Australian States
and Territories.1 Near-drowning urban and
rural hospital referral patterns are similar and are unlikely to have
contributed to the difference in Indigenous and non-Indigenous
rates. Reduced exposure of Indigenous children to domestic swimming
pools is a possible explanation. Further prospective research is
required to clarify these issues.
There are many reports of the high rates of drowning in children aged
0-4 years.1,2,9,11
In our study, children aged 0-4 years in the NT,
Queensland and the rest of Australia had rates of drowning and
near-drowning 5-10 times higher than children aged 5-14 years. Young
children in the NT appeared to be at greatest risk, with rates of
drowning and near-drowning nearly three times higher than the rest of
Australia and Queensland.
Rates of swimming pool drowning in children aged 0-4 years in the NT
were more than twice the Australian and Queensland rates and among the
highest in the world.2,8,9,11 The proportion of
children drowning in swimming pools in the NT was also statistically
higher than in Queensland and the rest of Australia. Drowning rescue
and resuscitation protocols in the NT are similar to those in the rest
of Australia. One possible explanation for the differences between
NT and Queensland rates of swimming pool drowning is that Queensland
introduced statewide pool fencing legislation in 1992, while pool
fencing laws in the NT are still inadequate. All the NT swimming pool
drowning deaths reported in this study occurred in pools with
non-Australian Standards fencing (NT coroner, personal
communication). There is no standard legislation for pool fencing in
the NT. Only one jurisdiction (encompassing less than 10% of the
population) requires fencing according to Australian Standards.
Other reasons for the disparity between NT and Queensland rates of
drowning could be differences in exposure to water, differences in
exposure to swimming pools, or differences in parental supervision.
Further prospective research is needed to investigate the role of
these different risk factors.
We may have underestimated rates of drowning and near-drowning, as
retrospective data were used and case ascertainment relied on coded
cause of death/hospitalisation. We may also have under-reported NT
rates of near-drowning, as the ratio of near-drowning to drowning in
the NT (2:1) was lower than Australia (9:1) and Queensland (9:1).
Smaller numbers of NT drowning and near-drowning cases also produced
considerable variation in annual NT data. However, statistical
analyses, including Poisson regression, enabled analysis of trend
over time.
In response to this study and other reports, NT injury prevention
groups are planning to expand their drowning prevention campaigns.
This will include lobbying the NT government to enact
isolation/four-sided pool-fencing legislation. More public
awareness campaigns are also planned. These will be directed towards
the need for effective pool fencing, parental supervision of young
children, and cardiopulmonary resuscitation skills, and will
include other measures that can assist in preventing drowning in
young children. Kidsafe NT also intends to use the information from
this study to develop a prospective drowning surveillance system.
This system will be used to evaluate drowning prevention
interventions and to further investigate NT risk factors for
childhood drowning, including the role of swimming pool fencing.
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Kidsafe, Child Accident Prevention Foundation of Australia, NT
branch, provided the funding for the data extraction by the
Australian Institute of Health and Welfare.
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None declared.
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- Moon L, Rahman N, Bhatia K. Australia's children: their health and
well being 1998. Canberra: AIHW, 1998. (AIHW Catalogue No. PHE 7.)
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Pitt WR. Increasing incidence of childhood immersion injury in
Brisbane. Med J Aust 1986; 144: 683-685.
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Cass DT, Ross F, Lam LT. Childhood drowning in New South Wales
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610-612.
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Vimpani G, Doudle M, Harris R. Child accident mortality in the
Northern Territory. Med J Aust 1988; 148: 392-395.
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Silva DT, Ruben AR, Wronski I, et al. Excessive rates of childhood
mortality in the Northern Territory. J Paediatr Child Health
1998; 34: 63-68.
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d'Espaignet ET, Kennedy K, Paterson BA, et al. From infancy to young
adulthood: health status in the Northern Territory, 1998. Darwin:
Territory Health Services, 1998.
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Spyker DA. Submersion injury epidemiology, prevention and
management. Pediatr Clin North Am 1985; 32: 113-125.
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Pitt WR, Balanda KP. Childhood drowning and near-drowning in
Brisbane: the contribution of domestic swimming pools. Med J Aust
1991; 154: 661-665.
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Geddis DC. The exposure of pre school children to water hazards and
the incidence of potential drowning accidents. N Z Med J 1984;
97: 223-226.
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O'Carrol PW, Alkon E, Weiss B. Drowning mortality in Los Angeles
County 1976-1984. JAMA 1988; 260: 380-383.
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Fergusson DM, Horwood LJ. Risks of drowning in fenced and unfenced
domestic swimming pools. N Z Med J 1984; 97: 777-779.
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Carey V, Chapman S, Gaffney D. Children's lives or garden
aesthetics? A case study in public health advocacy. Aust J Pub
Health 1994; 18: 25-32.
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Millner N, Pearn J. Will fenced pools save lives? A 10 year study
from Mulgrave Shire, Queensland. Med J Aust 1980; ii:
510-511.
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Intergov-WA, Intergovernmental Working Party on Swimming Pool
Safety. Preschool drowning in private swimming pools. Perth: Health
Department of Western Australia, 1988.
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US Department of Health and Human Services. The international
classification of diseases. 9th revision. Clinical modification
(ICD-9-CM). 3rd ed. Bethesda, Md: DHHS, 1989.
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Langlois JA, Buechner JS, O'Connor EA, et al. Improving the E
coding of hospitalizations for injury: do hospital records contain
adequate documentation? Am J Public Health 1995; 85:
1261-1265.
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Australian Bureau of Statistics. Population by age and sex,
Australian States and Territories. Canberra: ABS, 1997. (Catalogue
no 3201.0.)
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Australian Bureau of Statistics. Experimental estimates of
Aboriginal and Torres Strait Islander population 1991 and 1996.
Canberra: ABS, 1997. (Catalogue no 3230.0.)
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Pagano M, Gauvreau K. Principles of biostatistics. 1st ed.
California: Wadsworth, 1993.
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Frome EL, Checkoway H. Epidemiologic programs for computers and
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Stata Statistical Software [computer program]. Version 5.0.
Texas: Stata Corporation, 1997.
(Received 23 Feb, accepted 30 Jul, 2001)
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Territory Health Services, Casuarina, NT.
Karen M Edmond, FRACP, MMedSc (ClinEpid),
Community Paediatrician.
Centre for Epidemiology and Biostatistics, University of
Newcastle, Newcastle, NSW.
John R Attia, FRCPC, PhD, Senior Lecturer;
Catherine A
D'Este, PhD, Senior Lecturer.
Menzies School of Health Research, Casuarina, NT.
John T Condon, FAFPHM, MPH, Research Scholar.
Reprints will not be available from the authors.
Correspondence: Dr K
M Edmond, Research Fellow in Paediatric Epidemiology, London School
of Hygiene and Tropical Medicine, 50 Bedford Square, London, WC1B
3DP, UK.
karen.edmondATlshtm.ac.uk.
©MJA 2001
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© 2001 Medical Journal of Australia.
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| 3: Average annual
incidence of drowning and near-drowning for the rest of Australia and Queensland
compared with the Northern Territory, 1994-1997 |
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Northern Territory
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Australia
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Queensland
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Number |
Incidence* |
Incidence* |
IRR† (95% CI‡) |
Incidence* |
IRR (95% CI) |
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| Drowning |
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| 0-4 years |
16 |
22.61 |
3.71 |
6.17 (1.60-16.68) |
5.77 |
3.92 (0.94-12.48) |
| 5-14 years |
1 |
3.21 |
0.62 |
5.26 (0.12-33.48) |
0.82 |
3.91 (0.08-39.28) |
| Near-drowning |
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| 0-4 years |
32 |
45.21 |
20.69 |
2.19 (1.18-4.37) |
26.78 |
1.69 (0.70-3.52) |
| 5-14 years |
7 |
5.56 |
2.55 |
2.20 (1.26-8.30) |
5.36 |
1.03 (0.12-4.14) |
| Drowning and near-drowning |
| 0-4 years |
48 |
67.82 |
24.45 |
2.77 (1.40-4.91) |
32.55 |
2.13 (1.05-3.94) |
| 5-14 years |
8 |
6.44 |
3.61 |
1.78 (1.21-6.58) |
6.12 |
1.04 (0.12-4.08) |
| Swimming pool drowning and near-drowning |
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| 0-4 years |
40 |
56.51 |
15.65 |
3.61 (1.70-6.77) |
20.69 |
2.74 (1.24-5.47) |
| 5-14 years |
1 |
3.20 |
1.03 |
3.08 (1.75-18.7) |
2.63 |
1.22 (1.29-8.23) |
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| * Incidence per 100 000 children. † Incident
rate ratio. |
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(degrees per year of freedom)