Article Text

Traumatic and non-traumatic spinal cord impairment in New Zealand: incidence and characteristics of people admitted to spinal units
1. Sarah Derrett1,
2. Carolyn Beaver2,
3. Martin J Sullivan3,
4. G Peter Herbison1,
5. Rick Acland4,
6. Charlotte Paul1
1. 1Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
2. 2Burwood Academy of Independent Living (BAIL), Christchurch, New Zealand
3. 3School of Health and Social Services, Massey University, Palmerston North, New Zealand
4. 4Burwood Hospital Spinal Unit, Canterbury District Health Board, Christchurch, New Zealand
1. Correspondence to Dr Sarah Derrett, Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, PO Box 56, University of Otago, Dunedin 9056, New Zealand; sarah.derrett{at}otago.ac.nz

## Abstract

This paper estimates the incidence (all ages) of spinal cord neurological impairment (SCI; traumatic and non-traumatic) in New Zealand and describes pre-SCI characteristics and early post-SCI outcomes for participants (16–64 years) in this longitudinal study. Demographic and clinical data on all people admitted to New Zealand's two spinal units (mid-2007 to mid-2009) were included for the estimate of incidence. Participants in this longitudinal study were asked at first interview about pre-SCI socio-demographic, health and behavioural characteristics, and about post-SCI symptoms, general health status (EQ-5D) and disability (WHODAS 12-item). Age-adjusted incidence rates (95% CI) for European, Māori, Pacific and ‘Other’ ethnicities were 29 (24–34), 46 (30–64), 70 (40–100) and 16 (9–22) per million, respectively. Interviews with 118 (73%) participants (16–64 years), occurred 6.5 months post-SCI. Most reported bother with symptoms, and problems with health status and disability. Compared with Europeans, the incidence of SCI is high among Māori and particularly high among Pacific people. Six months after SCI, proximate to discharge from the spinal units, considerable symptomatic, general health and disability burden was borne by people with SCI.

• Spinal cord diseases
• burden of disease
• epidemiology
• disability
• rehabilitation
• cohort study
• outcome evaluation
• functional outcome
• longitudinal
• systematic review
• quality of life

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## Introduction

A longitudinal cohort study of people with spinal cord neurological impairment (SCI) in New Zealand is underway.1 New Zealand has no SCI register, and little is known about people with SCI in New Zealand—despite previously reported high rates of traumatic SCI and the impact on individuals and their families.1 ,2

This paper aims to: (1) estimate SCI incidence, for all ages, from a ‘census’ overview between 28 July 2007 and 6 August 2009; (2) describe characteristics of people admitted to either of New Zealand's two spinal units with SCI; (3) describe pre-SCI characteristics of participants in the longitudinal study (ages 16–64 years); (4) describe their early post-SCI symptoms, health and disability; and (5) explain modifications to our previously published protocol.1

## Methods

Demographic and clinical data on all people (all ages), admitted during the study period to either of New Zealand's two spinal units for the first time following acute impairment, were included for the estimate of incidence. Denominator data were obtained from Statistics New Zealand, 2006 Census.3

The longitudinal study aims to investigate how entitlement to rehabilitation and compensation affects socioeconomic and health outcomes for working-age people potentially able to access earnings-related compensation or invalid's benefits.1 Therefore, the longitudinal study recruited people aged 16–64 years, admitted to either spinal unit with SCI during a 2-year period. People were ineligible for the longitudinal study if the multi-disciplinary clinical team identified: cognitive or communication problems precluding an interview, prognosis of likely death within 6 months, other diagnoses precluding interview (eg, active psychotic disorder); they were not New Zealand residents; or they had no neurological damage at time of recruitment.

Nurses collected demographic and clinical information from clinical records of people admitted with SCI, and approached potential participants about the study. Contact details of consenting people were provided to our team, and interviewers scheduled a first interview, intended to occur 4 months after the date of SCI.

Nurse-collected data included: dates of birth, SCI and admission; unit (Auckland or Burwood), sex, ethnicity and the ASIA Impairment Scale (AIS) grade.4

Participants were asked about SCI and post-SCI characteristics including: SCI cause, wheelchair use and place of residence. Post-SCI EQ-5D health status and symptom bother (derived from the Secondary Complications Survey) was collected.11 Post-SCI disability was measured using the WHODAS II 12-item which assesses activity limitations and participation restrictions over the past 30 days with five responses (‘no/mild/moderate/severe/extreme or cannot do’ difficulty) for each item.12 ,13

## Results

Over two-years, clinical data were obtained for 238 people admitted to the two spinal units. Eight people were non-residents. Based on the remaining 230 residents, the estimated annual incidence rate (and 95% CI) of SCI in New Zealand was 30 (26–34) per million. Age-adjusted (to the total New Zealand population) incidence rates for European, Māori, Pacific, and ‘Other’ ethnicities were 29 (24–34), 46 (30–64), 70 (40–100) and 16 (9–22) per million, respectively.

For the longitudinal study, 76 were ineligible (10 aged <16 years, 42 aged >64 years, 7 unable to communicate, 3 the multidisciplinary clinical team advised no approach, 1 person died, 8 non-residents, 3 no neurological damage, 2 prognosis <6 months). Of the 162 eligible people, 118 participated (response rate=73%); 15 declined and 29 were non-contactable by interviewers following multiple contact attempts.14 Telephone (62%), or in-person interviews, occurred 6.5 months (median) after SCI (IQR: 4.8–7.6).

No statistically significant differences in age, sex, unit or AIS grade were observed between participants and non-participants (table 1). Fewer Māori and Pacific people participated according to ethnicity collected from their clinical record. At interview we collected self-reported ethnicity; six additional people identified as Māori (n=23; 19%). Pre-SCI characteristics are presented in table 2. For the 80 (68%) reporting income, median income was NZD$50 000 (IQR NZD$32 500–\$81 000).

Table 1

Characteristics collected from clinical records for those eligible for the longitudinal SCI study

Table 2

Pre-SCI characteristics of longitudinal study participants (n=118)

The reported cause of SCI and early outcomes are presented descriptively in table 3. Injury was the reported cause of SCI for most (87% for Māori, 60% for Pacific and 77% for non-Māori/non-Pacific ethnicities). Bother with listed symptoms was reported by more than half. Participants also reported bother with ‘other’ symptoms, including: temperature regulation, generalised pain, numbness and pressure areas. Most reported post-SCI problems with EQ-5D health status and moderate-to-extreme difficulty with seven of the 12 WHODAS items.

Table 3

Participants’ (n=118) SCI-related and post-SCI outcomes (median 6.5 months after SCI)

## Discussion

The annual incidence of SCI (traumatic and non-traumatic) in New Zealand of 30 per million was the same as the mean in a recent worldwide review.15 A systematic review based on 13 studies showed a range of incidence rates for traumatic SCI from 12.1 to 57.8 per million.16 An earlier study in New Zealand of SCI found a much higher incidence (49 per million), even though it did not include non-traumatic cases.2 It is likely that different methods of case ascertainment explains some of this difference (the earlier study used all hospital admissions for SCI with and without evidence of vertebral fracture). In our study, people in the acute phase would have been excluded from our study if they died before admission to a spinal unit. On the other hand, the earlier study found only 8% were complete SCI lesions, compared with 32% for the 16–64 years subgroup in our report. People with minimal neurological impairment and people with terminal-cancer-related SCI requiring palliative treatment prior to dying, are less likely to be admitted to a spinal unit. Given these differences in ascertainment, no conclusion can be drawn about changes in rates over time. Nevertheless, rates of SCI remain elevated among Māori (as the earlier study found) and a marked elevation was observed among Pacific people (2.4 times the European rate).

Results from the longitudinal study provide the first overview of people with SCI aged between 16 and 64 years admitted to New Zealand's spinal units. Participants differed from non-participants in relation to ethnicity only; when self-reported ethnicity was asked, the proportion reporting Māori ethnicity met our prior expectations.1 Fewer participants reported non-traumatic SCI than anticipated. This may be because our participants were aged 16–64 years, and non-traumatic SCI increases with age. People were interviewed slightly later than planned because of participants' preferences, interviewers' health and difficulty locating some participants following discharge. A range of pre-SCI characteristics were apparent. Six months after SCI, a large proportion experienced problems with symptoms, health status and disability.

A limitation of the study was the necessity for participants to ‘recall’ their pre-SCI health characteristics; collection of health status prospectively would require a nation-wide observational study with regular measurement points until the sub-group people experienced SCI. Other studies have found injured peoples' recalled pre-injury health status approximates their ‘recovered’ health status, and that recall may be preferable to using general population norms as a proxy for pre-injury health.17 ,18

Strengths of our study include high participation rates, collection of a wide range of pre-SCI characteristics, and inclusion of people with traumatic and non-traumatic SCI. Our longitudinal study was funded within a (previous) Health Research Council of New Zealand grant aimed at developing New Zealand's research capacity among people with disability. The principal investigator (MS), study interviewers (including CB), advisors and others, are people with SCI, as called for by people with SCI in the developmental phase of the project.1 ,19 ,20

This brief paper highlights: current incidence rates (especially the high incidence among Pacific people which needs further investigation), and symptomatic, general health and disability burden borne by, and of importance to, people with SCI proximate to the time of discharge from the spinal units to the community.20

Some burden, such as bother with constipation and pain, may be amenable to improvement. Future analyses of longitudinal data will examine relationships between participants' baseline characteristics and longer-term outcomes.

### What is already known on the subject

• Internationally, spinal cord neurological impairment (SCI) incidence has been shown to range between 12.1 and 57.8 per million; no publications have reported the incidence of SCI in New Zealand during the past 18 years.

• SCI, with neurological impairment, can be costly to society and burdensome to individuals and their families (financially, socially and in terms of poor health and disability outcomes).

• Often, the focus of research has been on clinical or longer-term SCI outcomes; little appears to be known about outcomes of importance to people with SCI, close to the time of discharge home.

### What this study adds

• The estimated incidence (and 95% CI) of SCI (traumatic and non-traumatic) in New Zealand is 30 (26–34) per million.

• Age-adjusted incidence rates were higher for Māori, and markedly higher for Pacific people, relative to Europeans.

• Considerable symptom, health and disability burdens are borne by people close to the time of discharge to the community from the spinal units.

## Acknowledgments

We are very grateful to all those who participated in this study. We thank: the past and present management team and staff at the Burwood Academy of Independent Living and the two spinal units (especially Dr Shridar Atresh, Dr Shaun Xiong, Marianne Cox, Julian Verkaaik and Mere Hibbs); the two nurses for the recruitment and clinical data collection—Karen Marshall (Clinical Nurse Specialist, Burwood Hospital Spinal Unit) and Karla Cooper (formerly of the Auckland Spinal Unit); and interviewers—Peina Tamou, Rob Courtney, and (the late) Pamela Fergusson; and especially Maureen Crawford the operational project coordinator. We also thank John Langley and Sue Wilson for their comments on an earlier draft of this paper.

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## Footnotes

• Funding This study is funded by the Health Research Council of New Zealand. The views and conclusions expressed herein are the authors' and may not reflect those of the funders.

• Competing interests None.

• Ethics approval This study was undertaken following approval from the New Zealand Health and Disability Multi-Region Ethics Committee.

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

• Data sharing statement This is the first paper from a longitudinal study. The research team are currently involved in further analysis using the data.

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