Article Text

Prospective outcomes of injury study
1. S Derrett1,
2. J Langley1,
3. B Hokowhitu2,
4. S Ameratunga3,
5. P Hansen4,
6. G Davie1,
7. E Wyeth5,
8. R Lilley1
1. 1
Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, New Zealand
2. 2
Te Tumu-School of Māori, Pacific and Indigenous Studies, University of Otago, New Zealand
3. 3
School of Population Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
4. 4
Department of Economics, University of Otago, New Zealand
5. 5
Ngāi Tahu Māori Health Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, New Zealand
1. Correspondence to Professor J Langley, Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, New Zealand; john.langley{at}ipru.otago.ac.nz

## Abstract

Background: In New Zealand (NZ), 20% of adults report a disability, of which one-third is caused by injury. No prospective epidemiological studies of predictors of disability following all-cause injury among New Zealanders have been undertaken. Internationally, studies have focused on a limited range of predictors or specific injuries. Although these studies provide useful insights, applicability to NZ is limited given the importance of NZ’s unique macro-social factors, such as NZ’s no-fault accident compensation and rehabilitation scheme, the Accident Compensation Corporation (ACC).

Objectives: (1) To quantitatively determine the injury, rehabilitation, personal, social and economic factors leading to disability outcomes following injury in NZ. (2) To qualitatively explore experiences and perceptions of injury-related outcomes in face-to-face interviews with 15 Māori and 15 other New Zealanders, 6 and 12 months after injury.

Setting: Four geographical regions within NZ.

Design: Prospective cohort study with telephone interviews 1, 4 and 12 months after injury.

Participants: 2500 people (including 460 Māori), aged 18–64 years, randomly selected from ACC’s entitlement claims register (people likely to be off work for at least 1 week or equivalent).

Data: Telephone interviews, electronic hospital and ACC injury data. Exposures include demographic, social, economic, work-related, health status, participation and/or environmental factors.

Outcome measures: Primary: disability (including WHODAS II) and health-related quality of life (including EQ-5D). Secondary: participation (paid and unpaid activities), life satisfaction and costs.

Analysis: Separate regression models will be developed for each of the outcomes. Repeated measures outcomes will be modelled using general estimating equation models and generalised linear mixed models.

## Introduction

The overall purpose of the proposed Prospective Outcomes of Injury Study (POIS) is to (a) determine factors leading to disability following injury in New Zealand (NZ) and (b) qualitatively explore with injured New Zealanders their “lived experiences” and perceptions of injury outcome. Results will have implications for (1) improved targeting of injured people at increased risk of experiencing poor outcomes, (2) improved health and social services for people following injury, and (3) improvement of national strategies to better address barriers to, and facilitators of, good outcomes identified by injured people.

### The international burden of injury

Globally, injury accounts for 9% of deaths.1 However, “…deaths due to injury represent only the tip of the injury iceberg” (p112).23 Of great importance to injured people, whānau (families) and communities is the daily experience of life after injury. After injury some people will experience a complete resumption of life as it was before injury; others will experience a life lived differently. A life lived differently is not necessarily a poorer life. Some people report life-enhancing opportunities arising as a consequence of their injury, such as the attainment of occupational or educational goals previously not available to them, or an increased sense of self-worth and belonging.4 However, others experience primarily adverse outcomes following injury and encounter barriers to living a “good life”.

### The concept of disability

Conceptualising and measuring pre-injury “life as it was” and the “life lived differently” is complex. For injury outcome research, current concepts of “disability” provide an appropriate focus. Definitions and understanding of disability have been, and are, contested.567 In NZ, “For most of the 20th century, disability was thought to be a problem inherent in individuals” (p8).8 From the 1960s, disability was seen to arise from “…environmental barriers and attitudes that specifically discriminate[d] against people with impairments”.91011 People with disabilities helped to develop an internationally accepted model, published by the World Health Organization (WHO) in 2001—the International classification of functioning, disability and health (ICF)12 (fig 1).

Figure 1

The World Health Organization International classification of functioning, disability and health (ICF) model.

The ICF provides a biopsychosocial health and disability framework, depicting functional impairments, activity limitations and participation restrictions influenced by the health condition (in our project’s case—injury), personal and environmental factors.13 The ICF dimensions have guided the selection of predictor and outcome measures for our project’s quantitative structured interviews and electronic data, and also themes to be explored in the in-depth qualitative interviews.

Although the ICF has been internationally commended,9131415 and increasingly used by researchers,1617 limitations have been identified. For example, the ICF does not sufficiently consider subjective experiences or quality of life.151819 In NZ it has been noted that “…Many consequences [of injury] are unable to be measured directly …, such as the loss of intimacy between spouses, or the breakdown of a family unit…”.20 To deliver important and innovative outputs, our project also includes measures of concepts beyond the ICF, such as happiness, life satisfaction and autonomy.21 And the qualitative component explores in greater depth with injured people, including Māori, their self-reported experiences, barriers and facilitators to good outcomes. Because the concept of disability is not fixed, the term “disability outcomes”, rather than “disability”, is used throughout this application.

### Disability in NZ

Results from the 2006 New Zealand Disability Survey (NZDS) are not yet available; however, in 2001, the NZDS estimated that 743 800 New Zealanders (20%) were living with a disability.22 Injury was the reported cause of one-third of this disability (34%).22 This survey was cross-sectional, producing point prevalence estimates. It does not provide estimates for the number of people with ongoing disability after injury (eg, 6 months or 1 year). At a personal and family level, Statistics New Zealand and Ministry of Health surveys reveal differences in household composition, income, employment status and educational attainment between people with a disability and the general NZ population.22

### Financial costs of injury

Injury is costly at both personal and societal levels; however, few studies have undertaken economic analyses of injury costs to individuals and society. Where these have been undertaken, they have tended to focus on the health system/insurer costs only23 or on specific injury types, eg, traumatic brain injury,24 or have short follow-up periods.25 Nilsen et al26 reviewed 12 cost-of-illness (COI) studies from eight different countries and found wide variation across the studies. Further, COI studies have been criticised for not taking into account intangibles such as pain and quality of life.26 One NZ study investigated the total documented costs for 15 ill or injured workers, and their families and workplaces, and found the costs since injury were $1 167 472 (average of$77 831) excluding both the loss of income borne by individuals and families and future costs to the Accident Compensation Corporation (ACC).20 ACC is NZ’s no-fault compulsory accident insurance scheme which accepts personal injury claims for physical injury and mental injury arising from a physical injury. ACC covers the cost of treatment and compensates for loss of earnings and permanent impairments. Entitlement claims largely exclude injuries resulting in less than 1 week’s incapacity or primary healthcare treatment-only claims. Entitlement claimants do not tend to be people with injuries requiring one or two visits to a primary healthcare professional only. ACC entitlement claims are for injuries serious enough to qualify for: earnings-related compensation (if too injured for paid employment for more than 1 week), home help, transportation support, or lump sum payments, etc (regardless of employment status). Referrals to ACC come from ACC-approved referrers including general practitioners, medical specialists, physiotherapists and other approved allied health professionals. (NB, ACC also insures visitors to NZ who are injured here—but visitors are not eligible to participate in our prospective project.)

### Previous research relevant to this proposal

Discussion of previous research by the applicants has been limited to injury-related disability outcomes work undertaken during a recently completed HRC Developmental Grant.

#### Establishing advisors to the project

Two groups of advisors have been formed: (1) “people with disability advisors” providing critical input to the project and having facilitated focus groups and pre-testing; (2) “scientific advisors” providing scientific and interpretive advice on aspects of the analysis.

#### Consultation with Māori

BH (Ngāti Pükenga) was an original member of the team awarded the HRC Developmental Grant. BH and SD travelled to the four regions where it is proposed to hold the study, to consult with Māori pakeke (advisors) about issues of importance for Māori regarding study design, research questions and desired outputs. It was acknowledged that injury, access to ACC and health services, and injury outcomes are problems for Māori in these regions. The potential merit of our project, making explicit the barriers to access and good outcomes, was identified. Pakeke also stressed the paramount importance of having an in-depth qualitative component running alongside the quantitative component—to get beneath the surface of key issues for Māori. There was also support for the larger quantitative component providing comprehensive empirical evidence capable of informing service providers and policy-makers—provided that sufficient Māori were recruited. To increase the Māori participation, a number of strategies were advised.

• Advice: Include regions where a high proportion of the injured are Māori. Researcher response: The four regions selected will provide 20% (n = 460) Māori participants (based on last year’s regional numbers).

• Advice: Pakeke-supported telephone interviews rather than postal survey for collecting information, but emphasised the need for some face-to-face interviews. Response: Budgeted for 10% of interviews to be face-to-face.

• Advice: Make the interviews bilingual. Response: We will.

• Advice: Appoint Māori interviewers; develop the regional workforce by appointing local Māori interviewers. Response: We will.

• Provide regular meetings to support local interviewers, and where possible, appoint interviewers via Māori organisations, for additional local support. Response: We will.

Consultation with Māori is ongoing, and will be extended to other people, provider groups and organisations during the pilot study and the proposed main study.

#### Consultation with policy-makers and other key stakeholders

JL and SD met with officials at the Ministry of Health, Ministry of Social Development, Statistics NZ and ACC. All were supportive of the study. Personal communications from these groups stressed the need for, and value of, a high Māori participation rate and benefits of offering face-to-face interviews alongside telephone interviews.

(1) Advice: Researchers need to collect information on ethnicity according to the NZ census. Response: We will.

(2) Advice: Collect information about pre-injury disability, as people with disabilities are more prone to injury. Response: We have added questions from NZ census about prior disability to our interviews.

(3) Advice: Pacific people are also a group with access and injury outcome problems. Response: We will collect ethnicity of all participants, and have budgeted for a Pacific Masters student to descriptively analyse (with supervision) Pacific (n = 180) data. We will also appoint a Pacific interviewer.

Consultation with officials also confirmed that our project did not duplicate any current research programmes and would contribute useful data.

#### Focus group

SD and an advisor held a focus group (tape-recorded and transcribed) with people with injury-related disabilities. The aim of this group was to identify key issues to ask of all injured participants and to obtain advice about the method of data collection.

(1) Issue: Telephone interviews of up to 1 h are acceptable and preferable to postal questionnaires. Response: Telephone, with some face-to-face, interviews will be used to improve response rates. Interviews kept to 45 min duration.

(2) Issue: Participants need to be aware they may (i) request a postal questionnaire and (ii) that people with attention/concentration difficulties maybe interviewed in shorter “bursts” over 2 or 3 days. Response: We will.

(3) Issue: Researchers must protect participants’ confidential personal data and be able to analyse results independently. Response: We will/are.

(4) Issue: Researchers need to include questions about psychological well-being, sexuality and “positives” such as happiness/life satisfaction. Experiences with health providers, ACC and employers also need to be included. Response: We will.

(5) Issue: What about the perspectives of family/partners (also raised by pakeke)? Response: We have included open-ended questions in the interviews to allow people to raise the perceived impact on their family/whānau; and specific questions about the satisfaction with the inclusion of whānau by service providers. In-depth qualitative interviews with sub-samples of participants will allow closer exploration of this issue. Unfortunately, the cost of interviewing family/whānau of each injured participant in this first NZ prospective study of injury outcomes is prohibitive.

#### Electronic data from ACC

These will include the referring professional’s diagnosis, nature, cause and type of injury, date of injury, prior injuries to same or different parts of the body, nature and duration of any ACC support provided (case management, health treatments and earnings-related compensation information). Data will be collected at the end of the study follow-up period.

#### Electronic data from New Zealand Health Information Services (NZHIS)

These will be collected if the injured participant was admitted to hospital as a result of their injury at any time during the 12-month project follow-up period. NZHIS data will include ICD-10 diagnosis, injury-related procedure codes, and dates and length of stay in hospital. Members of the research team are extremely familiar with both electronic databases.

### Data analysis

Descriptive analyses of variables of interest (eg, proportions of people in different age groups, sex, ethnicities and regions) will be performed. The main analyses will be separate linear or logistic regression analyses, undertaken for each of the outcomes of interest. These models will look at the direct effects of the postulated predictors on the outcomes, after adjustment for confounders and mediators. Predictors in these models will include variables from each of the domains that might be expected to influence the outcome, eg, socioeconomic, injury severity, personal factors, psychosocial factors, job and skill factors. It is expected that many of these variables will have different effects in subgroups of subjects, so many of these models will have interaction terms included. Some of the predictor variables will be continuous, and, if their relationship with the outcome is not linear, they will be transformed by using fractional polynomials.

When considering the outcome at more than one follow-up point, these models will be extended to cope with repeated measurements, so will be mixed models, general estimating equation models, and generalised linear mixed models depending on the exact situation. We anticipate that there will be complex pathways and interactions between some of the variables.11 Therefore, in secondary analyses we will explore some of these by examining the direct and indirect effects of variables on the outcomes using structural equation models.

We will estimate the personal, health sector and ACC costs of injury-related disability. Data on participants’ financial costs associated with their injury-related disability will be appropriately aggregated and extrapolated to derive estimates of these financial costs for NZ as a whole. Analysis will also address the acknowledged deficit of COI studies by incorporating the HRQoL burden of injury through derived estimates of HRQoL quality-adjusted life years lost and regained.60

## Potential sources of error

### Selection bias

There is a risk that injured people who consent to participate in the study will differ from non-participants, introducing bias. We have provisional approval from ACC to collect information about certain characteristics of the non-participants, including age, sex, region they live in, date of injury, injury site/cause and severity, and, if employed, occupation. This will enable us to compare participants and non-participants on a range of variables. In the same way, we will also assess any differences in loss to follow-up, to be accounted for in the interpretation of results. As part of our current pilot study, we are seeking advice from injured people as to how we might increase participation rates and minimise loss to follow-up.

### Measurement bias

Recall bias is a potential source of error, particularly in relation to measurement of pre-injury status. We have sought to minimise this by collecting pre-injury information within 1 month of the injury event. Collection of health and disability outcomes, costs and health service utilisation data is also limited to a 30-day recall period to reduce recall bias. The prospective study design minimises recall bias for other factors. Misclassification of outcome data is a possibility, as the study has no control over coding secondary datasets (ie, ACC, NZHIS). For ACC, there are financial incentives, which help to ensure that the data are of high quality (eg, ACC would not be paying earnings-related compensation for those who return to work). Similar comments apply to NZHIS (eg, hospital reimbursements for days’ stay). Further, Injury Prevention Research Unit staff have recently completed a study which shows that the quality of NZHIS coding is high.62

### Confounding

Information will be collected on possible confounders (eg, comorbidity and prior health status), and analytical methods will be used to control for these factors.

### Generalisability

Significant relationships between risk factors and outcomes of interest are likely to apply to most subpopulations of injured people, and, although the size of the effects may differ, the direction of effect is likely to remain the same.

### Sample size and power

To produce stable estimates of coefficients in regression, models require at least 10 cases for every included variable for linear regression and 10 cases with the outcome for logistic regression. So with binary outcomes, such as return to work or normal activities, we require 10 people not achieving this for each variable (binary or continuous) that is included in the model. It is generally accepted that about 4 times as many cases are needed to detect an interaction as are required to detect a main effect. Thus for two variables and their interaction, at least 60 cases are required for stable estimates. If we assume that 10% will not have returned to work or normal activities at any follow-up point, then the inclusion of 2000 subjects in the model (200 failures) would allow six variables and their two-way interactions to be included in the model before uncertainty arose about the estimates. We expect at least this many variables in most models. With linear regression, many more variables would be allowed in the model, and this would give more scope for examining interactions and more complex relationships. Thus 2000 people would be a minimum for many of the interesting models that will be used to give stable estimates of the coefficients. Allowing for a conservative 80% follow-up rate over 1 year means at least 2500 people need to be interviewed at baseline. We will actively follow participants (using alternative named contacts if people move and a website for study updates) and aim for a 90% follow-up rate over the 12 months. Feedback from stakeholders and the developmental focus groups indicated that the \$10 voucher per completed interview would be appreciated and would help to increase participation and follow-up rates.50

On the basis of entitlement claimants in each of the study regions for the last financial year, we anticipate recruiting at least 460 Māori and 180 Pacific participants. This would give at least 80% power to detect statistically significant differences in proportions of 8% or more between Māori and non-Māori and 12% or more between Pacific and non-Pacific groups.

## Qualitative component methods and analysis

### The qualitative approach

As mentioned above, the aim of the qualitative component is to describe the lived experiences of New Zealanders with injury-related disability outcomes. Qualitative methods allow a more in-depth (rich) description and examination of the factors impacting on outcomes following injury. Although some research has considered the experiences and outcomes for people following injury, as with much of the quantitative research on injury-related disability outcomes, this has focused on particular service provider issues and specific types of injury and has been cross-sectional in nature or not necessarily relevant to NZ. To locate people’s experiences within a NZ context—and to be focused on the issues as experienced and “lived by” the participants—a phenomenological and collaborative story-telling approach has been selected.46364

### Participants

We intend to recruit a subsample of at least 30 participants from the quantitative component of the study to participate in in-depth qualitative interviews: 15 Māori from the Ngāi Tahu takiwā (tribal region) and 15 non-Māori. (Māori participants will not necessarily be of the Ngāi Tahu iwi (tribe).) Purposive selection will ensure that we include people from a range of ages, sexes, injury types, households, geographical areas, service providers, and socioeconomic and employment status. The lived experiences and outcomes of every injured person are important. However, our particular emphasis upon the experiences and outcomes for injured Māori reflects our commitment to the Treaty of Waitangi and our understanding that a qualitative epistemology is appropriate for research with Māori. Furthermore, consultation with Māori has identified the need for rigorous empirical Māori data to support policy improvements for Māori and to improve cognisance regarding Māori perspectives towards disability concepts,29 and also to identify the particular obstacles that Māori are known to experience in accessing appropriate and timely services and attaining good outcomes.

### Methods

Qualitative data will be collected from at least two in-depth face-to-face interviews, 6 and 12 months after injury. (Using the phenomenological and interpretive approach, people will be encouraged to contact the interviewers between the 6 and 12 month interviews if they have additional experiences to report.) Participants’ and, as appropriate their whānau, post-injury stories will be followed for 1 year after injury. (Feedback from Māori pakeke (advisors) is that the interview methods need to be flexible enough to include whānau members’ perspectives if the participants feel this is appropriate, meaning more than 15 Māori participants may be included.) In-depth interviews will, with participants’ consent, be tape recorded and fully transcribed.

Instead of a structured interview format, which is typically prescriptive, phenomenological story-telling allows participants to raise issues of greatest importance to them.6566 A phenomenological approach may therefore allow us to understand and describe alternative disability concepts located outside the WHO ICF model.18 However, there are certain themes we wish to explore in the qualitative interviews. If these themes are not spontaneously raised in the course of the interviews, participants will be prompted at the end of their stories. The key themes, informed by the literature and by our consultation, focus group and pre-testing include the story of the injury itself (cause, impact and trajectory), the impact on family/whānau/others, work (positives and negatives), costs (psychosocial and financial), spiritual supports, racism, ease of access to health services, satisfaction with health/ACC and social services and professionals, barriers encountered, strategies for overcoming these, and the facilitators of good outcomes.

### Qualitative analysis

The analytical framework is interpretive and narrative.6467 There is debate in the literature about the advantages of exclusive adherence to participants’ verbatim accounts versus the benefits of shared (researcher–participant) interpretation, understanding and meaning. Our project will follow the approach outlined by Bishop6368 of sequential interviews and shared construction of meaning between researchers and participants. Māori and non-Māori strands of the qualitative component will be analysed separately to ensure that Māori results have primary importance to, and for, Māori.69 If important shared themes emerged across the two arms of the qualitative component, a subsequent joint analysis may be undertaken if appropriate.

### POIS overall data management and storage

All personal identifiable study information will be kept in a locked filing cabinet accessible to study investigators only. Electronic data from ACC/NZHIS will be stored according to agency protocols.

## Relevance to health

This project’s relevance to health is demonstrated by strong links to key NZ health strategy documents. For example, the project directly relates to the New Zealand Disability Strategy (NZDS, 2001) Objective 1 (to encourage and educate for a non-disabling society), by acknowledging that disabled people are experts of their own experience (rather than relying on perspectives of clinicians or other providers). Other examples include the project’s examination of whether or not injured people with disabilities: experience the same employment conditions, rights and entitlements as everyone else; have an adequate standard of living; receive respectful treatment from government departments; receive quality information; feel at the centre of service delivery; have timely access to services. The project also directly relates to the HRC Injury, Impairment, Rehabilitation and Disability Strategy by: (i) using the internationally accepted WHO ICF model for the study data collection, including social and environmental factors; (ii) empirically examining a crucial information gap that exists in NZ about the disability outcomes of injured New Zealanders; (iii) contributing to the identification of strategies for “eliminating or reducing the likelihood of adverse injury-related consequences”. Crucially, to identify strategies for improving post-injury outcomes, we first need to know where the barriers to good outcomes lie. This first prospective study to identify predictors of outcomes for New Zealanders will directly address this knowledge deficit—comprehensively (through the quantitative component) and in rich detail (through the qualitative component).

## Relevance to Māori health outcomes

Injury is an important issue for Māori.28297071727374 Personal communication from ACC, Ngāi Tahu Research Consultation Committee and pakeke confirm that: (1) injury, access and outcomes for Māori are of concern; (2) more information on barriers to access and good post-injury outcomes for Maori is a research imperative. This project has a strong Māori component evaluating disability barriers to, and facilitators of, positive outcomes for Māori. It uses methods acceptable to Māori and includes methods for collecting participants’ perceptions about the level of inclusion of their whānau by service providers. Importantly, this study acknowledges both the Treaty of Waitangi and He Korowai Oranga (2002) by adhering to the Treaty principles (derived from the Treaty Articles) of: (1) partnership (Māori co-investigators contributing to study design, methods, data collection and analysis); (2) participation (consulting with pakeke and groups in the proposed study regions and adopting their recommendations; contributing to local workforce development by employing Māori interviewers in each region of the study); (3) protection (the research team intends results to have a positive impact on health outcomes for injured Māori and their whānau; interpretation of results for Māori undertaken by Māori investigators). The project, taking on board as it has advice from pakeke and senior Māori officials, also relates closely to Ngā Pou Rangahau Hauora Kia Whakapiki Ake Te Hauora Māori (2004) and Vision Mātauranga (2005), by providing information of direct relevance to Māori and their communities about barriers to access, examples of service and ACC provider strengths (and weaknesses), and the quality of life outcomes for Māori after injury.

## Dissemination of results

An abstract from the developmental work has been submitted to a National Conference on Rehabilitation for consideration, and a paper is now being prepared for journal submission. Results from the main study will be shared with study participants by postal lay summaries and the project website. Results will also be disseminated by, and discussed with, pakeke, Māori and Pacific providers, organisations and stakeholders—by face-to-face presentations and written reports. Results will be published in national and international peer-reviewed journals and presented at conferences.

## Footnotes

• Funding This study is funded by the Health Research Council of New Zealand and the Accident Compensation Corporation, Wellington, New Zealand.

• Competing interests None.

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

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