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| Journal of the New Zealand Medical Association,
08-October-2004, Vol 117 No 1203
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Low back pain in young New Zealanders
David McBride, Dorothy Begg,
Peter Herbison, Ken Buckingham
Low Back Pain (LBP) has been described as the most common,
most costly and disabling musculoskeletal
condition.1 Since World War 2, a dramatic
increase in LBP disability has been observed, at a rate disproportionate to all
other health conditions.2 In New Zealand, this
is reflected by the numbers of, and costs to, the Accident Compensation
Corporation (ACC) for back pain claims—in 2000–2001, 10,968 new
claims cost $30 million and 6,660 ongoing claims cost $68
million.3
The majority of persons with LBP recover within 2 months,
but 2–3% eventually develop disabling chronic LBP
(DCLBP)1—these patients accounting for
80% of the costs of compensation. LBP, therefore, has major socioeconomic
implications; with many of the tangible costs related to disability and
compensation.
This aim of this study was to describe the frequency,
severity, and economic impact of LBP in a birth cohort of individuals now aged
26.
MethodThe study was part of the
Dunedin Multidisciplinary Health and Development Study, which has been described
in detail elsewhere.4 In summary, it is an
ongoing follow-up of approximately 1,000 young people who were born in Dunedin
over a 12-month period in 1972 and 1973. The cohort has been studied at birth,
at age 3, every 2 years to age 15, then at ages 18, 21, and 26.
The demographics of this group, and their physical and
mental wellbeing, have been carefully documented. The LBP data were collected by
interviewer-administered questionnaire during which study members were asked
about the number of episodes of LBP occurring in the previous 12 months and
consultations with health professionals. For the worst episode of LBP, details
were sought on occupation, time off work or job limitation, the severity of the
discomfort (as measured on a visual analogue scale with a maximum score of 100),
and disability (as measured by the modified Oswestry
questionnaire).5
ResultsOf the 980 study members
interviewed, 969 completed the LBP questionnaire. 524 individuals, 244 of the
477 females (51% of females), and 280 of the 492 males (57% of males) indicated
that they had experienced LBP in the previous 12 months, the frequency of
occurrence of which is shown in Table 1.
Table 1, How often LBP (low back pain) was experienced
in the previous 12 months.
LBP severity showed a bimodal distribution with a median of
49 and modal values of 25 and 65 (Figure 1). There was some evidence that those
who had more frequent episodes suffered from higher reported discomfort (Figure
2).
The answers to the disability questions indicated a small
but significant number of individuals with severe impairments. Thirteen
indicated that they could not look after themselves because of pain and
seventeen avoided walking. Eleven indicated that pain prevented them from
sleeping at all. One individual was chronically disabled by back pain and unable
to work for most of the year.
There was a similar proportion of individuals with back pain
in the employed and non-employed groups—and for the 448 with a current
occupation, there was no difference in the distribution of LBP between those
with professional, clerical and technical jobs and those with production or
trades jobs.
Fifty-six individuals with LBP had to have time off work
because of discomfort. These individuals reported more severe pain (mean score
of 71) than those who did not take days off (mean score of 46); the difference
being statistically significant (t=9.6, p=000) Of these 56 individuals, 45
consulted a health professional. The 11 who did not consult took 3 days or less
off work. The majority had relatively short periods off work; 26 (43.3%) had 1
or 2 days, 41 (72%) taking less than 7 days. There were, however, 11 individuals
(28%) who took more than 1 week off from work. Of those that did not have time
off work, 158 indicated that LBP affected their work by either slowing them down
or necessitating a change in their duties. There was evidence (Figure 3) that
those who had more frequent episodes tended to take more time off
work.
Figure 1. Distribution of pain severity
 Figure 2. Relationship between the mean severity of
discomfort (visual analogue scale) and the number of episodes of LBP in the
previous year
 Figure 3. Relationship between the mean number of days
off work and the number of episodes of LBP in the previous year
 The indirect costs to the economy can be estimated in that
the 448 respondents (who had a job in the year prior to assessment) lost a total
of 665 days of work through illness due to back pain, implying a total number of
days lost per working person as approximately 1.5 days per year. The average
weekly earnings of 25–29 year old New Zealanders in paid employment was
$676 (before tax) in
June 2003.6 Assuming a 5-day working week,
daily earnings for this age group are $135 (before tax), and the value of the
annual loss of working days per person in employment is approximately
$203.
Of those individuals with symptoms, 150 (29%) sought
treatment—with 37 individuals consulting a physician as sole treating
practitioner, 11 consulting a chiropractor, 8 consulting a physiotherapist, and
3 consulting an osteopath. There were 15 ‘other’ health
professionals (masseurs) providing the sole source of advice Fifty-one
individuals sought advice from a treatment team, most commonly a
physician/physiotherapist combination. The remainder sought advice from multiple
sources.
DiscussionIn the planning phase of this study,
evidence from an earlier cross sectional study in New
Zealand7 suggested that there would be at least
a 20% prevalence of LBP during the previous year. The high rate of LBP in this
young group might therefore be viewed as a source of concern, but the prevalence
alone does not give the whole picture because it varies according to the
question asked and the target population.
In international studies, the peak frequency of lifetime LBP
occurs in the age range 30–55 years,8
which differs according to the prevalence period, possibly illustrating a
‘recall’ effect for more recent
events.9
In the Life in New Zealand (LINZ)
study,7 the annual prevalence was highest for
young males aged 15–18 (44%); the figures for the 19–24 and
25–44 year old groups being 20% and 17% respectively. The prevalence of
‘ever’ having LBP was, however, highest in the 45–64 year old
group (67%). There is no satisfactory explanation of why this pattern of
reporting should appear, but it seems likely that different biomechanical
factors are responsible in the different age groups.
At the most simplistic level, there are a number of
‘pain generators’ in the lower back, the disc being thought
responsible for approximately 36% of back pain cases; facet joints for 15%; the
sacroiliac joint 30%; and the remaining 19% assumed to be soft tissue injuries
or a combination of pathologies.8
The cumulative trauma
model8 was developed due to increasing
acknowledgement that acute and chronic LBP are different (with soft tissue
injuries being more likely in the younger age groups and degenerative changes
more likely in the older age groups). This model fits with what is known about
occupational LBP, because the onset is gradual and frequently not related to an
‘accidental’ cause.8
It is important, because of the cumulative trauma model, to
focus on more outcome-specific measures rather than the simple presence or
absence of pain. Thus, LBP can be described in terms of duration, frequency, and
disability—attributes which describe the ‘severity’ or
importance of an attack.
Duration of the attack is obviously important, and
restricting the outcome to LBP that lasts for at least 2 weeks obviously
indicates a more significant event. Such LBP has a lower prevalence of around
14%.10 Duration of time off work is also a
predictor of chronicity; those off work for 1 month having a 20% risk of
long-term disability.11 The frequency of
attacks is also indicative of chronicity: the 22% prevalence of attacks
occurring ‘most days’ in this study seems high until one looks at
the daily reporting in LINZ for the 15–18, 19–24, and 25–44
year age groups (which was 28%, 33%, and 11%
respectively).7
Disability is arguably the most important occupational
indicator, and the fact that a small but significant proportion of such a young
population experienced severe disability should be cause for concern. LBP with
onset early in life is thought to be indicative of a poor long-term outlook,
especially if associated with a long initial
episode.12 The reaction to a first episode of
LBP is also important, with growing evidence that pain associated with fear
leads to a poor outcome.13
An inability to work has consequences not only for the
individual but also for society. Although the cost per working individual was
only NZ$203, there were 1,956,000 individuals in employment in the March 2004
quarter,14 so a current estimate of the annual
loss to the economy in this age group is NZ$396 million. If ACC costs are
estimated at NZ$100 million, then the total (excluding the costs of healthcare
not funded by ACC) will be nearly NZ$500 million.
Due to the social and economic consequences, it should be
important to identify those persons ‘at risk’, but the search to
identify individual risk factors has been very disappointing to date.
Although our data do not support any clear association
between occupation and risk, occupational factors are important. A National
Institute of Occupational Safety and Health review
panel15 identified 40 research papers looking
at the relationship between LBP and physical workplace factors. They found
‘strong’ evidence that LBP was linked to whole-body vibration and
work-related lifting/forceful movements, and that LBP is associated with heavy
physical work and work-related awkward postures. The review also emphasises the
point made earlier—LBP is not a uniform entity, it is complex, it means
different things at different ages, and it has to be looked at in different
contexts.
For future epidemiological studies, we will have to define
what ‘clinically significant’ LBP is, and develop standardised tools
and questionnaires to detect this outcome. The results of studies can then be
directly compared. We must also be very clear what we are looking for, and
specific factors (for example, vibration or posture) must be carefully defined
and measured prospectively to clarify dose-response relationships and to
‘unmask’ occupational effects.
What should be done about it? LBP is a common life
experience, but can become costly and disabling. Because of the lack of clear
risk factors, primary prevention has been disappointing, and the positive
benefits of any single treatment modality have been uncertain. As a result, some
researchers have suggested that occupational factors are relatively unimportant
and that LBP is a symptom not a disease.16,17
Current advice from the Accident Compensation Corporation and the New Zealand
Guidelines Group, outlined in the New Zealand Acute LBP
Guide18 is that the best treatment is to get
the individual back to work. There is, however, a danger in this approach.
Because of all the confusion about what LBP is, or means,
one can be led to ignore the biomechanical model. This is where the conundrum
lies: because the trauma is cumulative the occupational link is not clear, and
although the best treatment for someone in employment may be to get the
individual back to work, the work may have caused the condition in the first
place and needs to be assessed. The New Zealand Acute LBP
Guide18 states:
It is important to discuss work activities,
especially those involving heavy lifting, bending or twisting, that may have
contributed to the original problems. Alternative duties and/or workplace design
may need to be discussed with the worker and/or employer.
Some LBP ‘patients’ show fear-avoidance beliefs,
and avoid activities which are predicted to cause an increase in pain and
suffering.19 Graded exposure to work activities
in the acute phase may help to avoid chronic pain in some
individuals,19 but this obviously requires
active workplace intervention. The busy family physician will not usually have
time for this and should be willing to refer. Our data indicates that this does
seem to happen relatively often, a physician and physiotherapist
‘team’ being the commonest combination. We advocate that at least
one member of the team should be familiar with the work.
Work-related and physical factors are, however, low in the
hierarchy of LBP risk factors. The psychological and social elements are
pre-eminent, and undoubtedly important in maintaining disability. We now propose
to look at these factors (particularly their temporality) in relation to the
occurrence of back pain within the cohort. Some of the most important elements
will be previous psychiatric disorders identified using the Diagnostic Interview
Schedule,20 and the social variables which have
been measured using instruments such as the life history
questionnaire.21
The value of the cohort in looking at the natural history of
LBP will now be clear: the high prevalence of LBP at this early stage does not
seem not to bode well for the future. It is, in our view, very important to
define exactly what we mean by LBP and to identify what we think is causing it.
The natural history can then be investigated properly and preventive measures
designed.
Author information:
David McBride, Senior Lecturer in Occupational Health, Department of Preventive
and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin;
Dorothy Begg, Senior Research Fellow in Injury Prevention, Injury Prevention
Research Unit, Department of Preventive and Social Medicine, Dunedin School of
Medicine, University of Otago, Dunedin; Peter Herbison, Associate Professor
in Biostatistics, Department of Preventive and Social Medicine, Dunedin School
of Medicine, University of Otago, Dunedin; Ken Buckingham, Associate
Professor in Health Economics, Department of Preventive and Social Medicine,
Dunedin School of Medicine, Dunedin.
Correspondence:
David McBride, Department of Preventive and Social Medicine, University of
Otago, PO Box 913, Dunedin. Fax: (03) 479 7298; email: mcbride@gandalf.otago.ac.nz
References:
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