Journal of the New Zealand Medical Association, 14-December-2007, Vol 120 No 1267
Non-fatal work-related motor vehicle traffic crash injuries in New Zealand: analysis of a national claims database
Shaheen Sultana, Gillian Robb, Shanthi Ameratunga, Rod T Jackson
International studies indicate that motor vehicle traffic crash (MVTC) injuries are one of the leading causes of work-related fatalities.1-4 MVTC injuries whilst at work are considered to be the single largest cause of occupational fatality in United Kingdom.5 In the USA, they represent from 20 to 25% of work-related fatalities; 25% in Denmark, Finland and Sweden; 30% in Canada; 49% in Australia; and 60% in France.6,7
Death due to MVTCs also comprises the single largest category of work-related deaths in New Zealand. McNoe et al8 in their recent report on work-related traffic fatalities in New Zealand reported that there are on average 31 such deaths annually, occurring at a rate of 2 per 100,000 workers per year.
Data on fatal injuries are easier to ascertain and analyse, but deaths are a small fraction of the overall burden of injury, i.e. the tip of the injury pyramid. In New Zealand, approximately 230,000 compensated work-related injuries were reported in the financial year commencing 1 July 2001.9 Despite considerable human and economic consequences, non-fatal work-related (WR) MVTC injuries in New Zealand have received scant attention.
Research in this field is challenged—at least in part—by varying levels of attention to the coding of the ‘place of injury’ category in hospital discharge data and the lack of a single agency that has the responsibility of collecting information on all WR MVTCs resulting in injuries.10 However, the New Zealand Injury Prevention Strategy (NZIPS) has identified road traffic and workplace injuries among its six priority areas,11 the implementation of which requires better information on non-fatal injuries to inform preventive strategies.12
The present study aims to contribute to the current gap in knowledge by providing a profile of non-fatal WR MVTC on public roads in New Zealand between 2004 and 2006—as identified through the ACC claimants’ database. The ACC claimant database is theoretically the most complete national register of WR MVTC injuries that require medical care and/or earnings-related compensation, including non-hospitalised injuries.
The Accident Compensation Corporation (ACC) administers New Zealand’s Accident Compensation Scheme, which provides personal injury cover for all New Zealand citizens, residents, and temporary visitors to New Zealand no matter who is at fault. ACC operates under the Injury Prevention, Rehabilitation and Compensation (IPR&C) Act 2001 that came into force on 1 April 2002. A claimant in ACC is thus defined as a person who has cover for a personal injury under the IPR&C Act 2001.13
Work-related non-fatal MVTC injuries resulting in ACC claims between July 2004 and June 2006 were identified from the ACC Motor Vehicle Account. The initial dataset of approximately 50,000 cases was contained in a single Microsoft Excel data file. In addition to a narrative description of the crash, the dataset contains information regarding the crash date, claim registration date, whether the injury was work-related, occupational and industry class, injury diagnostic codes, and sociodemographic characteristics of the claimant—specifically age, sex, and ethnicity.
The study sample was defined using the following eligibility criteria:
The latter code is initially determined from the response on the ACC45 claim form “did the accident occur at work” and subsequently confirmed by ACC staff to be an injury defined as work-related by the IPR&C Act 2001. The selection procedures for all cases for WR MVTC injury from the initial dataset are shown in Figure 1.
Figure 1. Process of case selection from the ACC claimants’ database
Demographic details (age, gender, and ethnicity); injury details (prior activity, injury diagnoses, and body part injured), work details (employment status, work type, industry, and occupation); and cost of claims were measured. The definitions and limits noted below are based on operational definitions provided by ACC.
Age—Age in years is at the date of injury. Age was categorised as 15–24 years, 25–34 years, 35–44 years, 45–54 years, 55–64 years, and 65 years or above.
Ethnicity—The information for this variable is based on the claimants’ response to the question, “what is your ethnic background” on the ACC45 claim form. Ethnicity was then grouped into European (European not further specified, NZ European/Pakeha, Other European), Maori, Pacific (Pacific Islander not further defined, Samoan, Cook Island Maori, Tongan, Niuean, Tokelauan, Fijian, Other Pacific Islander), Asian (Asian not further defined, Southeast Asian, Chinese, Indian, Other Asian), and others (Middle Eastern, Latin American/Hispanic, African, Other).
Injury diagnosis—The ACC diagnosis maps the type of work-related injury from either “Read”14 or “ICD” codes, supplied by the treatment provider (Usually, ICD from hospitals and Read from general practitioners). This in-house diagnostic variable applied by ACC was used in these analyses.
There were 12 different diagnostic groups in the dataset which were re-grouped into 5 categories.
Employment status—Self-employed, or working for another person or entity, i.e. an employee.
Types of work—Based on the claimants’ response to the question. “What type of work do you do?” from the ACC 45 claim form. The self-identified categories listed in the form include: sedentary (brief standing and walking), light (mainly standing and walking), medium (often lift 5 kg plus), heavy (often lift 9 kg plus), and very heavy (often lift 22kg plus).
Cost of claims—The payments made by the ACC to the injured worker, or next of kin, or the cost to the ACC of the treatment or service provided. The costs shown here are exclusive of New Zealand’s Goods and Services Tax (GST). There are three modes of payments. “Entitlement claims” involve entitlement payments (e.g. weekly compensation for lost remuneration at work, rehabilitation payment) to the injured person. “Medical fee only claims” refer to payments to recognised treatment providers, such as, doctors, physiotherapists, or pharmacists.
Costs of treatment provided at hospitals (e.g. Accident and Emergency departments or in-patient services) are covered through bulk-funding agreements with the District Health Boards and recorded in the “other payments” category.
Industry—Coded according to the Australian and New Zealand Standard Industrial Classification, ANZSIC 199615.
Occupation—Coded according to the New Zealand Standard Classification of Occupations, NZSCO 1999.16
Descriptive analyses were undertaken for each variable. Where appropriate, 95% confidence intervals (CIs) were computed for comparing proportions. Claim incidence rates per 100,000 person years and 95% CI were calculated where suitable denominator data were available. Population rates were calculated using the Census-2001 data as the denominator. Denominators were the number of persons of working age employed in the labour force, specified by age, gender, occupation, and industry.
Age-standardisation was undertaken by the direct method, using the Segi population. All values expressed as integers are rounded to the nearest whole number unless otherwise specified. Data were analysed using STATA statistical software (version 8.2).17
The study was approved by the Multi-region Ethics Committee, Wellington.
A total of 3867 claims representing 3749 individuals associated with WR MVTC injuries were identified from the ACC Motor Vehicle Account over the 2-year period 2004–2006 (Figure 1). Of these individuals, 102 claimants submitted 2 claims and 8 claimants submitted 3 claims. While some of these could be a new claim for a new incident, it was not possible to distinguish between a new claim and a repeated claim from the dataset provided. However, given the small number of these claims, all claims were assumed as independent claims.
The estimated overall age-standardised rate of WR MVTC injuries on a public road, between 2004 and 2006, was 109 per 100,000 workers per year.
WR MVTC injuries occurred mostly in males (75%) and in New Zealand Europeans who comprised 67% of total injuries in the claims database. In the 10-year age bands from 15 years and older, the greatest number of worker injuries occurred in the 35–44 age group (28%) with an overall mean age of 39 years. The distribution by recorded age, gender, and ethnicity of the claimants including age-standardised rate is presented in Table 1.
Table 1. Work-related motor vehicle traffic crash injury (July 2004–June 2006): demographic characteristics of the claimants
Age-specific census data was not readily available for ethnicity grouping for people in the labour force; therefore age-standardised rates by ethnicity were not calculated. There was no clear pattern observed in age-specific rates except for a sharp decline in the ≥65 year age group (Figure 2).
The majority of the claimants were diagnosed as having soft tissue injuries (strains and sprains), accounting for 69% of WR MVTC injuries, with a further 12% being lacerations (Figure 3). In terms of body part injured, more injuries affected the neck (27%) than any other bodily location, followed by head and face including ear and eye, shoulder including clavicle (19%); and back/ spine (12%).
Figure 2. Work-related motor vehicle traffic crash injury: age-specific rates (95% CI)
Figure 3. Work-related motor vehicle traffic crash injury: injury diagnosis
The majority of injuries identified from this database occurred among paid employees (86%) and to those who were engaged in medium (34%) and heavy (29%) activity work (Table 2).
Transport workers were the most frequent victims of work-related injuries (an age-standardised rate of 390 per 100,000 per year) and accounted for about 14% of the total injuries (Table 3). ‘Road freight transportation’—sub-grouping of “Transport and Storage Industry”, had a particularly high number of workers injured (n=311) followed by ‘road passenger transportation’ (n=149) over the 2-year period. Relatively high rates were also observed among workers in mining; communication; and electricity, gas, and water supply industries.
Table 2. Work-related motor vehicle traffic crash injury: employment status
Table 3. Work-related motor vehicle traffic crash injury: major industry (ANZSIC 1996) classification
Among the major occupational classes, approximately one in three WR MVTC injuries occurred in ‘plant and machine operators and assemblers’ with a corresponding high rate of WR MVTC injuries (an age-standardised rate of 422 per 100,000 per year) (Table 4). This group includes industrial plant operators, stationary machine operators and assemblers, drivers, and mobile machinery operators, and building and related workers. Among them, ‘drivers and mobile machinery operators’ (not surprisingly) had the highest number of injuries (n=1126).
Table 4. Work-related motor vehicle traffic crash injury: major occupation (ANZSCO 1999) classification
The total cost associated with the 1968 claims made for the 1-year period from 1 July 2004 to 30 June 2005 was approximately NZ$6 million, with an average total cost per claim of NZ$2884. Of the total cost, 360 entitlement claims (average of NZ$14,808 per claim) accounted for the majority of payments. The remainder included an average of NZ$237 for medical fee only payments, and NZ$65 for other payments.
The cost of claims for males (n=1457) was greater than for those by females (n=511), with males averaging NZ$3520 per claim and females averaging NZ$1071 (Table 5).
Table 5. Work-related motor vehicle traffic crash injury: cost of claims by age and gender
Workers aged 35–44 years incurred the largest proportion of claims (approximately 30%) (Table 5); however, claims were most expensive in the 55–64 year age group with an average cost per claim being NZ$5254.
During the 2-year period commencing 1 July 2004 an average of 1934 claims annually were lodged with ACC for WR MVTC injuries, thus representing an age-standardised rate of 109 claims per 100,000 workers per year. Claimants were predominantly male (75%), NZ European (67%), and 35–44 years old (28%).
Surprisingly, younger workers were not at increased risk compared with older workers given the importance of younger age as a major risk factor for motor vehicle injury in general. Soft tissue injuries (strains and sprains) and injuries affecting the neck were particularly common. Transport workers (14%) and the ‘plant and machine operators and assemblers’ (32%) had the highest number of injuries. The total cost associated with the 1968 claims made for the 1-year period (July 2004–June 2005) was NZ$6 million, with an average total cost per claim of NZ$2884. To our knowledge, this is the first published analysis quantifying the burden of WR MVTC injuries in New Zealand.
There are important limitations to this study that could significantly compromise the validity of the results. Since data were obtained from an administrative database for managing claims, there was minimal data on other factors that could have helped elucidate causes of injuries. The number of ACC claims is also likely to be an underestimate of the total number of injuries experienced by the New Zealand population for several reasons.
The ACC captures information only on medically attended injuries and work-related injuries treated in the Accident and Emergency department are not included in the database.18 Furthermore, previous publications have referred to major concerns regarding the reliability and coding of the work-related indicator.19 20 Information regarding the reasons for the trip during which the crash occurred is often incompletely recorded in this database which primarily exists for administrative purposes.21 In previous research using the same database, Driscoll et al9 reported that only 5–10% of all claims for motor vehicle injuries were work-related.
Commuter and bystander injuries, the events most likely to have been underestimated, are not defined as WR MVTC injuries according to the current legislation (the IPR&C Act 2001). McNoe et al8 have reported that commuting fatalities comprised a significant proportion (44%) of all work-related road traffic deaths.
The Auckland Car Crash Injury Study22 reported that 15% of all drivers in serious crashes in 1998–9 in the Auckland region were commuting and another 5% were working at the time.21 In addition, Langley et al,23 in their more recent report, identified work-related bystander deaths as a significant hidden problem in New Zealand and reported that they represent approximately 52% of the total work-related fatalities.
The issues noted above highlight the major difficulties posed by varying definitions of WR MVTC injuries. For example, in some European countries, commuters are included within this definition while in the United States, Canada, the United Kingdom, the Netherlands, Denmark, and Norway commuting injuries are excluded from many operational definitions of work-related injuries.6
In New Zealand, a previous study8 investigating work-related fatal traffic injuries included injuries sustained during commuting to and from work, as well as an “activity during a recess period (e.g. at lunch time), at an employer’s sponsored social function and during training or a non-work period if the incident arose because of work.”
A further limitation of these analyses relates to the ethnicity coding. While an injured worker can list more than one ethnic group in an ACC claim form, in contrast to the Census, the ACC allows only one ethnic group to be coded.24 To avoid the resulting biases, a standardised approach to ethnicity coding should be implemented that is consistent with the Census and recommended by the Ministry of Health.25
The majority of the injuries in this analysis could be considered as “minor” with respect to the threat to life and the average cost of claims. However, some of these injuries can pose a significant threat to disability, contribute substantially to the overall injury burden,26–28 and be responsible for a high societal cost.29
Whiplash type neck injury caused by MVTCs, were common in this analysis (27%), and can have long-term disabling effects including adverse psychologic and social consequences.30
Despite the limitations, the findings of our report are consistent with previous studies. In a study of work-related fatal traffic injuries in New Zealand by McNoe et al8 males had more fatalities and with a peak frequency of occurrence in the 35–44 year age-group as in our study.
In several studies6–8 the industry with most fatal work-related injuries was transport. In the McNoe study,8 40% of the fatalities occurred in the ‘transport and storage industry’. However, the heterogeneity in national data collection procedures including issues related to case definitions and differences in the medico-legal contexts makes any between country comparisons of questionable validity.
Based on Statistics NZ data compiled from Traffic Crash Reports, drivers in the 15 to 19 year age group are 7 times more likely to crash (per 100 million kilometres driven) than drivers in the 45 to 49–year old age group.31 Our analyses showed no age-effect on WR MVTC injuries which may indicate that the major causes of WR MVTC injuries differ from non-WR MVTC injuries. While an alternative explanation is that more of the work related driving is done by workers in older age-groups, it seems unlikely that this would be sufficient to account for the ‘disappearance’ of the expected substantial age effect.
We have recently completed a systematic review32 that also suggests a different pattern of risk factors between work and non-WR MVTC injuries. For example, alcohol—an established risk factor for driving in general—may not be as important a factor in the context of work-related driving, potentially due to codes of practice and policies at workplaces. In contrast, .distraction may be more important for work-related driving where people spend more time in their vehicle and are likely to be operating under time pressure to meet deadlines for appointments or delivery of goods.
In conclusion, the relatively high incidence of WR MVTC injury claims identified in some industries and some demographic groups highlights the importance of WR MVTC injuries within the overall burden of work-related injury in New Zealand. The contribution of minor injuries to the overall injury burden should be taken into consideration while identifying targets for prevention. These findings also suggest there may be potential to target prevention interventions through both road safety and occupational health and safety procedures.
Given the shortcomings and inconsistencies identified, it is recommended that the process, content, and coding of data collection be reviewed. If substantial improvements can be made both completeness and quality can be achieved, these data collections could provide valuable information to plan and evaluate prevention strategies.
Competing interests: None
Author information: Shaheen Sultana, Research Associate; Gillian Robb, Senior Tutor; Shanthi Ameratunga, Associate Professor; Rod T Jackson, Professor and Head; Section of Epidemiology & Biostatistics, School of Population Health,
University of Auckland, Auckland
Acknowledgements: This work was funded by the ACC. We also thank Colin Cryer of Injury Prevention Research Unit, University of Otago, for his comment on an earlier draft.
Correspondence: Shaheen Sultana, Research Associate, Section of Epidemiology & Biostatistics, School of Population Health, University of Auckland, Private Bag 92019, Auckland 1001, New Zealand. Fax: +64 (0)9 373 7503; email: firstname.lastname@example.org
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