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| Journal of the New Zealand Medical Association,
13-September-2002, Vol 115 No 1161
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Self-reported injury rates in New Zealand
Carolyn Coggan, Rhonda Hooper and Brian Adams
Injury is a major public health problem in New Zealand. In
1998/99 injury was the third leading cause of hospitalisation, resulting in 68
472 public hospital discharges.1 However,
injury hospitalisations represent just a small fraction of the injury problem.
In 2000/01 the Accident Compensation Corporation (ACC) paid compensation for 1.4
million new claims, at a cost of $1.2 billion.2
This figure includes payments for 2.3 million GP visits and 2.2 million
physiotherapist visits. As well as the financial cost of injury, and the
resulting burden on the health system, there is also a huge social cost of
injury in terms of pain and suffering.3 Serious
injury can also result in long-term disability. The 2001 Household Disability
Survey estimated that 30% of all disabilities are caused by
injury.4
Few studies have reported on the epidemiology of
non-hospitalised injuries in New Zealand. A 1996/97 New Zealand Health Survey
found that 26.8% of adult respondents had sought medical treatment for an injury
in the previous twelve months.5 However, this
survey asked only whether the respondent had been treated for
any injury, and not the total number of
injuries occurring during the reference period. Although ACC data are another
potential source of information on non-hospitalised injury, detailed information
on the circumstances of the injury event is only available for entitlement
claims (14% of paid claims in 2001).2 In
addition, ACC data are not collected in a consistent manner across years. For
example, in 1999/2000 ACC did not provide cover for all workplace
injuries,2 resulting in an underestimate of
workplace and total injury for that period.
Consequently, unlike information on injury deaths and
hospitalisations, little is known about the nature and incidence of other
injuries. The current study aimed to obtain baseline information on the
incidence and nature of self-reported injuries in New Zealand.
MethodsThe survey was conducted
between the months of September and November 2001 as part of an ongoing
evaluation of a national injury prevention programme. A computer-assisted
telephone interviewing system (CATI) was used to randomly select approximately
400 households from each of 13 Territorial Local Authorities across New Zealand,
giving a total sample size of 5282 households. The adult (18+ years) in the
household with the next birthday was asked to complete a phone interview of
10–15 minutes in length. Up to eight call-backs were made to each
household. The response rate for the survey was 65%.
The interviewers asked respondents: “Has anyone living in your household required medical treatment by a doctor in the previous twelve months for any of these injuries: - an injury caused by a
fall;
- an injury caused by lifting an object; - an injury after being physically hurt by someone else; - an injury caused by poisoning (excluding food poisoning); - an injury caused by a motor vehicle crash; - an injury sustained while playing sport (other than a fall); - any other injuries (specify cause).” These injury categories were based on the leading
causes of injury as identified from hospitalisation data and ACC claims data.
Free text information on the mechanism of ‘other’ injuries was used
to reassign injuries that should have been listed under another injury
category.
If the respondent reported that someone in the household had been injured, the following details were then collected: the number of times that an injury event occurred; the number of household members injured on each of these occasions; the age and gender of each injured person; whether the injured person had to stay overnight in a hospital; the location where the injury occurred (except for motor vehicle crashes and sports-related injuries, as pilot testing found that these occurred on a public road, and at a sporting venue, respectively); and whether the injury resulted in a fatality. Only cases of non-fatal injury will be considered in this article. In order to make the definition of ‘injury’ used in this article consistent with the reporting of injury hospitalisation data, one case of injury is defined as one person who sustains one or more injuries in a single injury event. For example, if three household members sustained multiple injuries in a single motor vehicle crash, this was counted as three cases of injury. Denominator data for calculation of injury rates were collected by asking respondents to report the number of people in each age group currently living in their household. Whilst it is possible that the number of people living in each household could have changed during the 12-month recall period for injuries, it was beyond the resources of this study to collect details on changes in household composition. Similarly, details of the gender composition of the household were not collected due to time constraints on the questionnaire. All data were analysed using SAS Version 8.1 for Windows. Chi-squared tests were used to test the hypothesis that the venue of the injury event and injury severity would differ by gender and age. Chi-squared tests were also used to compare sample demographics to 1996 Census data6 for the regions sampled. Ninety five per cent confidence intervals for the injury rates were calculated assuming a Poisson distribution. ResultsFemales accounted for 57.6% of the
respondents, and while this was slightly higher than the percentage of females
reported by Census data (51.3%), the gender
distributions did not differ significantly. With regard to
the size of the households sampled, 19.5% were single occupant households and
this did not differ significantly from the composition of households in the
Census data (21.3% single occupant households). The age structure of the people
in the households sampled was compared to Census data and no significant
difference in distribution was found (sample: 0–4 = 7.2%, 5–14 =
16.4%, 15–24 = 14.6%, 25–64 = 51.7%, 65+ = 10.0%; Census: 0–4
= 7.1%, 5–14 = 14.2%, 15–24 = 15.9%, 25–64 = 50.5%, 65+ =
12.2%).
Table 1. Breakdown of injury types
Forty one per cent of the respondents reported that someone
in their household had sustained a medically-treated injury during the previous
twelve months. In total, 3578 non-fatal injuries were reported, an overall
injury rate of 24 497 per 100 000 population. Eight per cent of the injuries
required overnight hospitalisation. Twenty nine per cent of all injuries
occurred at home; 28% occurred at a sporting venue; 16% occurred at work; 4%
occurred at school; 4% occurred on a public road and 19% occurred at another
location. As shown by Table 1, falls accounted for one third of all reported
injuries. Sports-related injuries (28%) and lifting an object (16%) were also
common. Males accounted for the majority (58%) of the injuries. Table 2 shows
that young people aged 15–24 had the highest rate of injury (31 946 per
100 000), followed by adults aged 25–64 years (25 073 per 100
000).
The patterns of where injuries occurred differed
significantly by gender (p < 0.001), with females more likely to be injured
at home (41%) than males (21%), and males more likely to be injured at work
(male 20% vs female 11%) and sports venues (male 34% vs female 19%). The
location where injury events occurred also differed significantly by age group
(p < 0.001). As shown in Figure 1, young children and older people aged 65+
were most likely to be injured at home, and young people aged 15–24 were
most likely to be injured at a sporting venue. Older people aged 65+ were
significantly more likely to be admitted overnight to hospital (20%) than all
other age groups (0–4 = 4%, 5–14 = 6%, 15–24 = 8%, 25–64
= 6%, p < 0.001). No significant gender differences were found for hospital
admission.
Table 2. Reported injury rates by type of
injury
* = Number of injuries; † = rate per 100 000
person years; ‡ = 95% confidence interval
Figure 1: Age group comparison of where injuries
occurred
 Falls
Seventeen per cent of the respondents reported that someone
in their household had suffered a fall-related injury during the previous 12
months, resulting in a total of 1186 injuries. The falls were most likely to
occur at home (41%), followed by work (10%) and school (9%). A significant
proportion of the falls occurred at an unspecified location (39%). Ten per cent
of the injured persons were admitted overnight to hospital. Table 2 shows that
older people aged 65+ had the highest rate of fall-related injury (12 852 per
100 000), followed by children aged 5–14 years (10 597 per 100 000).
Females (52%) accounted for slightly more fall injuries than males.
Sports-related
injuries
Twelve per cent of the respondents reported that someone in
their household had suffered a sports-related injury during the previous 12
months, resulting in a total of 996 injuries. Five per cent of the injured
persons were admitted overnight to hospital. As shown in Table 2, young people
aged 15–24 years had the highest rate of sports-related injury (16 183 per
100 000), a rate more than double the next highest age group, children aged
5–14 years (7718 per 100 000). Males (72%) were much more likely to suffer
a sports-related injury than females.
Lifting
injuries
Nine per cent of the respondents reported that someone in
their household had suffered an injury caused by lifting an object during the
previous 12 months, resulting in a total of 568 injuries. Half of the lifting
injuries occurred at work, 40% occurred at home, and nine per cent occurred at
an unspecified location. Four per cent of the injured persons were admitted
overnight to hospital. Adults aged 25–64 had the highest rate of lifting
injury (6219 per 100 000, Table 2), followed by older people aged 65+ (2955 per
100 000). Males (58%) accounted for more of the lifting injuries than
females.
Violence
Two per cent of the respondents reported that someone in
their household had been injured as the result of physical violence inflicted by
another person. A total of 141 injuries were recorded. Thirty five per cent of
these intentional injuries occurred at home, and fourteen per cent occurred at
work. A large proportion (37%) occurred at an unspecified location. Ten per cent
of the injured persons were admitted overnight to hospital. Table 2 shows that
young adults aged 15–24 had the highest rate of injury due to physical
violence (1450 per 100 000), followed by pre-school children (1040 per 100 000).
Males (55%) sustained more of the violent injuries than females.
Motor vehicle
crashes
Two per cent of the respondents reported that someone in
their household had been injured in a motor vehicle crash, resulting in a total
of 128 injuries. Twenty one per cent of the injured persons were admitted
overnight to hospital. Table 2 shows that young adults aged 15–24 had the
highest rate of injury caused by motor vehicle crashes (1824 per 100 000),
followed by adults aged 25–64 (913 per 100 000). Males (57%) accounted for
more motor vehicle injuries than females.
Cutting and
piercing
Two per cent of the respondents reported that someone in
their household had suffered a cutting or piercing injury, resulting in a total
of 117 injuries. Seven per cent of the injuries required overnight
hospitalisation. More than half (57%) of the injuries occurred at home; 27%
occurred at work; and 15% occurred at an unspecified venue. As shown in Table 2,
adults aged 25–64 had the highest rate of cutting and piercing injury (966
per 100 000), followed by older people aged 65+ (893 per 100 000). Males
accounted for the majority (62%) of these injuries.
Unintentional
poisoning
Less than one per cent of the respondents reported that
someone in their household had been unintentionally poisoned. A total of 50
poisoning episodes were recorded and 18% of these cases required overnight
hospitalisation. Just over half (52%) of the poisonings occurred at home; 18%
occurred at work; and 26% occurred at an unspecified venue. Table 2 shows that
pre-school children had the highest rate of unintentional poisoning (473 per 100
000), followed by young adults aged 15–24 (421 per 100 000). Males
accounted for the majority (64%) of the poisonings.
Other
injuries
Seven per cent of the respondents reported that someone in
their household had suffered another type of injury. A total of 392
‘other’ injuries were recorded, and included incidents such as
burns, animal bites, being struck by a person or object, overexertion, foreign
bodies in the eye, and repetitive strain injuries. Six per cent of the injuries
required overnight hospitalisation. Forty five per cent of the injuries occurred
at home; 30% occurred at work; and 20% occurred at an unspecified venue. Table 2
shows that older people aged 65+ had the highest rate of ‘other’
injuries (3711 per 100 000), followed by adults aged 25–64 (3017 per 100
000). Males accounted for the majority (56%) of these other injuries.
DiscussionInjury is a public health problem
in New Zealand and this study provides previously unknown information on the
incidence and nature of injuries at the lower end of the injury severity
pyramid. While ACC data provide a measure of injury incidence, detailed
information is only available for entitlement claims, which are likely to under
represent children, the unemployed, homemakers and the
elderly.2 Findings from the current study
extrapolated to the New Zealand population would indicate that each day 2500
people sustain an injury serious enough to require medical treatment by a
doctor. This study also found that only 8% of the reported injuries resulted in
overnight hospitalisation, indicating that the total burden of injury in New
Zealand is much larger than estimated by routinely collected injury
hospitalisation data. As reflected by hospital discharge
data,7 this study found that people were most
likely to be hospitalised for motor vehicle crashes (21%), falls (10%) and
violence (10%).
It should be noted that this survey was not a random sample
of all New Zealanders, and is representative of the regions surveyed only.
Comparisons of the sample demographics with Census data indicated that the
households sampled were representative of the regions surveyed. It is also
possible that the data were subject to recall bias. Several other studies have
found a decline in recall of injury events when comparing a 12-month recall
period to shorter periods, thereby resulting in an underestimate of the annual
injury rate.8–10 To improve recall in
this study, the interviewers read out a list of different injury mechanisms and
this may have helped respondents to remember a greater number of injuries. The
respondents may also have been less likely to recall less medically serious
incidents of injury,8–10 and injuries due
to physical violence may have been under reported due to the sensitive nature
and/or legal implications of such incidents. Whilst it is acknowledged that the
question on physical violence did not specifically include the word
“intentional”, pilot testing demonstrated that respondents
associated this question with injury intentionally inflicted by another person.
A limitation of this study is that respondents may not have been aware of all
injury incidents for their household.
As with NZHIS hospital discharge
data,7 the leading cause of injury reported in
this study was falls (33%). However, the other leading causes of injury –
sports and lifting of objects – differed from the second and third leading
causes of injury hospitalisation – motor vehicle crashes and cutting and
piercing.7 One explanation for these
differences relates to the E codes used within the hospital coding system, as
the ICD-9 coding system does not easily identify sports-related
injuries.11 It is also likely that the
differences in ranking are due to the fact that while sporting and lifting
injuries appear to be the most common self-reported injuries, they also tend to
be less severe (5% and 4% were hospitalised respectively), compared to injury
events such as motor vehicle crashes (21% hospitalised).
The finding that 29% of the injuries occurred at home
indicates a need for health promotion programmes that emphasise the importance
of safety in the home. Older people and parents of pre-school children would be
particularly suitable target groups for such initiatives, given that these age
groups are most likely to be injured at home. Since these age groups may have
high levels of contact with general practitioners, GP consultation could provide
an opportunity for counselling on injury prevention practices.
Sports injuries accounted for more than one quarter of all
injuries, indicating a need for ongoing targeting of people involved in sports,
especially those in the 15–24 age group. Sixteen per cent of the injuries
occurred at work. Injuries caused by lifting, and cutting and piercing often
occurred as the result of work-related activities and more than one third of
injuries in the 25–64 age group occurred in the workplace. These findings
highlight the need for continued effort to ensure safety in workplace
environments. It is important to acknowledge that while females were more likely
to be injured at home, it was not ascertained whether these women were in paid
work at the time of their injury. However, from an injury prevention
perspective, the home is an important target regardless of activity.
It was of some concern that pre-school children had the
second highest rate of injury inflicted by another person. This reinforces the
need to support current efforts to increase the early identification and
management of at risk children.12,13 It was
also surprising to find that 14% of injuries caused by physical violence
occurred in the workplace. Internationally, workplace violence has been
identified as an important public health
issue.14 However, in New Zealand this issue has
received little attention from policy makers, employer organisations, unions or
the media. Further investigation is needed to ascertain the circumstances
surrounding these events, so that appropriate preventive strategies can be
developed.
The findings from this study highlight the need for injury
prevention activities to continue to occur in general practice. These could take
the form of one-to-one discussion with patients regarding the prevention of
further injuries, as well as dissemination of injury prevention pamphlets in
surgery waiting rooms.
Author information:
Carolyn Coggan, Director; Rhonda Hooper, Research Fellow, Injury Prevention
Research Centre, University of Auckland; Brian Adams, Programme Manager,
Accident Compensation Corporation, Wellington
Acknowledgements:
The Injury Prevention Research Centre acknowledges the funding support it
receives from the Accident Compensation Corporation, the Health Research Council
of New Zealand, and the Ministry of Health.
Corresponding author:
Carolyn Coggan, Injury Prevention Research Centre, University of
Auckland, Private Bag 92019, Auckland. Fax: (09) 373 7057; email: c.coggan@auckland.ac.nz
References:
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