FROM:
Spine J. 2015 (Apr 1); 15 (4): 675684 ~ FULL TEXT
Paul S. Nolet, DC, MS, MPHa, Pierre Cote, DC, PhD, Vicki L. Kristman, PhD,
Mana Rezai, DC, MHS, Linda J. Carroll, PhD, J. David Cassidy, DC, PhD, DrMedSc
Department of Graduate Education and Research,
Canadian Memorial Chiropractic College,
6100 Leslie Street,
North York, Ontario, Canada. M2H 3J1.
BACKGROUND CONTEXT: Current evidence suggests that neck pain is negatively associated with health-related quality of life (HRQoL). However, these studies are cross-sectional and do not inform the association between neck pain and future HRQoL.
PURPOSE: The purpose of this study was to investigate the association between increasing grades of neck pain severity and HRQoL 6 months later. In addition, this longitudinal study examines the crude association between the course of neck pain and HRQoL.
STUDY DESIGN: This is a population-based cohort study.
PATIENT SAMPLE: Eleven hundred randomly sampled Saskatchewan adults were included.
OUTCOME MEASURES: Outcome measures were the mental component summary (MCS) and physical component summary (PCS) of the Short-Form-36 (SF-36) questionnaire.
METHODS: We formed a cohort of 1,100 randomly sampled Saskatchewan adults in September 1995. We used the Chronic Pain Questionnaire to measure neck pain and its related disability. The SF-36 questionnaire was used to measure physical and mental HRQoL 6 months later. Multivariable linear regression was used to measure the association between graded neck pain and HRQoL while controlling for confounding. Analysis of variance and t tests were used to measure the crude association among four possible courses of neck pain and HRQoL at 6 months. The neck pain trajectories over 6 months were no or mild neck pain, improving neck pain, worsening neck pain, and persistent neck pain. Finally, analysis of variance was used to examine changes in baseline to 6-month PCS and MCS scores among the four neck pain trajectory groups.
RESULTS: The 6-month follow-up rate was 74.9%. We found an exposure-response relationship between neck pain and physical HRQoL after adjusting for age, education, arthritis, low back pain, and depressive symptomatology. Compared with participants without neck pain at baseline, those with mild (β=1.53, 95% confidence interval [CI]=2.83, 0.24), intense (β=3.60, 95% CI=5.76, 1.44), or disabling (β=8.55, 95% CI=11.68, 5.42) neck pain had worse physical HRQoL 6 months later. We did not find an association between neck pain and mental HRQoL. A worsening course of neck pain and persistent neck pain were associated with worse physical HRQoL.
CONCLUSIONS: We found that neck pain was negatively associated with physical but not mental HRQoL. Our analysis suggests that neck pain may be a contributor of future poor physical HRQoL in the population. Raising awareness of the possible future impact of neck pain on physical HRQoL is important for health-care providers and policy makers with respect to the management of neck pain in populations.
KEYWORDS: Cohort study; Disability; Epidemiology; Health-related quality of life; Neck pain; Risk
Evidence & Methods
Context
Prior research has demonstrated a negative association
between chronic neck pain and Health Related Quality
of Life (HRQoL). The studys authors sought to examine
this fact in a more robust fashion, using a longitudinal
study involving a population of patients in Saskatchewan,
Canada.
Contribution
The authors maintain that chronic neck pain is associated
with worse physical HRQoL but not mental HRQoL. The
authors postulate that chronic neck pain may be a contributor
to poor physical HRQoL in the population.
Implications
As the authors correctly recognize, a degree of response
bias may be impacting their findings. Furthermore,
although prior work was largely cross-sectional, the
follow-up in this analysis was limited to only six months.
The temporality of the data may also be a concern and
the fact that the study was conducted in Sakatchewan
could also impair the generalizability of the results. Cultural,
demographic and socioeconomic factors unique to
the Canadian province may be qualitatively and quantitatively
different from other populations in Canada and
elsewhere. These factors could alter the extent to which
neck pain is perceived, reported and considered to impact
HRQoL.
The Editors
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From the FULL TEXT Article:
Introduction
Over the past two decades, neck pain has become the
fourth leading worldwide cause of years lived with disability
[1]. Neck pain is common in the general population affecting
71% of adults during their lifetime [2, 3]. The 12-month prevalence
of neck pain in adults varies from 30% to 50% [3].
Neck pain is commonly associated with activity limitations
and disability [36]. The prevalence of neck pain peaks in
middle-aged groups during the most productive years of a
persons life. The annual incidence of neck pain in the general
population varies depending on the definition of neck pain
used. In Saskatchewan, Canada, neck pain had an annual incidence
of 146 per 1,000 subjects. In South Manchester, UK,
the reported annual neck pain incidence was 179 per 1,000
subjects [3]. Neck pain has a chronic recurrent course with
more than one-third of the population suffering from persistent
neck pain annually [4].
Health-related quality of life (HRQoL) is a concept used
in the health research to determine the impact of a disease
on individuals and can help inform researchers, clinicians,
and health policy makers. Health-related quality of life incorporates
physical, mental, and social well-being rather
than just defining health as the absence of disease [7]. Findings
from a cross-sectional analysis of the Saskatchewan
Health and Back Pain Survey suggest that neck pain was
weakly associated with worse physical HRQoL and not associated
with mental HRQoL [8]. However, it remains unclear
whether neck pain is a risk factor or an outcome of
poor HRQoL. To our knowledge, only one study has reported
that incident musculoskeletal disorders may have a
negative effect on future physical HRQoL [9]. However,
this association has not been examined prospectively in individuals
with neck pain. The primary goal of our study
was to determine whether neck pain is associated with
worse HRQoL at follow-up in a general population cohort
of adults from Saskatchewan. In addition, the crude association
between the course of neck pain and the change in
HRQoL between baseline and 6 months was examined.
Discussion
The purpose of this study was to measure the association
between neck pain and future HRQoL. Our results suggest
that neck pain is associated with physical HRQoL and that
the association follows a negative gradient from no neck
pain to intense disabling neck pain. Controlling for baseline
PCS HRQoL reduced this association. These results add to
the findings of a previously published cross-sectional study
from the Saskatchewan Health and Back Pain Survey and
confirm the presence of an association between neck pain
and physical HRQoL [8]. The magnitude of the negative association
between neck pain and physical HRQoL is larger
in the cohort than previously reported in the cross-sectional
analysis. This is likely because of the prevalence-incidence
bias present in the cross-sectional analysis. Furthermore,
the cross-sectional analysis reported comorbid conditions
as potential confounders [8]. In our prospective cohort,
musculoskeletal comorbidities and depression were the
most important confounders of the association between
graded neck pain and future physical HRQoL.
Our analysis supports the findings by Roux et al. [9] who
found that incident musculoskeletal disorders were associated
with reduced physical HRQoL compared with ageand
sex-matched controls. Most importantly, our final model
shows a clinically significant relationship between graded
neck pain and physical HRQoL at 6 months. The difference
in PCS scores from having no neck pain to severe neck pain
(grades IIIIV) is of similar magnitude to substantial clinically
important differences for both neck and arm pain after
surgery [24] and arthritis after treatment [33].
Although there was a substantial crude relationship between
neck pain severity and mental HRQoL, we did not
find an association after adjusting for digestive problems,
headaches, low back pain, and depressive symptomatology.
This is in contrast with the findings of Roux et al. [9] of a
weak association with mental HRQoL, although they did
not adjust for depression. In our final model, depressive
symptomatology was a substantial confounder, that is, it explained
much of the association between crude neck pain
severity and mental HRQoL. However, it should be noted
that there is some reason to believe that depressive symptomatology
may be a mediator rather than a confounder of
the neck pain and/or mental HRQoL association. Depressive
symptomatology has been shown to have a bidirectional
relationship with neck pain [34, 35]. Thus, to the extent
that depressive symptomatology is a risk factor for onset
of neck pain, it could be considered as a confounding variable,
as it was in the current analysis. However, there is also
a strong theoretical and empirical knowledge base that
depression is a consequence of pain [34, 36].
Thus, an alternative
view would be that, rather than being a confounder
of the neck pain and/or HRQoL association, depressive
symptomatology actually serves as a mediator of that association.
With depressive symptomatology as a mediator, the
effect of neck pain severity on mental HRQoL would be
through neck pains effect on depression. If this is the case,
and depressive symptomatology is actually on the causal
pathway between neck pain and HRQoL, adjusting for depression
would have introduced rather than reduced bias,
thus masking a true association [37]. Because of the theoretical
and empirical justifications for both views (depressive
symptomatology as a confounder or as a mediator),
we chose the more conservative analysis strategy of adjusting
for confounding, thus opting to err on the side of underestimating
the association. In reality, depressive
symptomatology is likely to be a confounder and a mediator.
Therefore, the true impact of neck pain on mental
HRQoL likely lies between our crude and adjusted
estimates.
Controlling for baseline PCS in the final PCS model reduced
the association with neck pain grade by improving
PCS scores by 5.39 points in grades III to IV neck pain
and 1.73 points in Grade II neck pain. In the PCS final model,
adjusting for baseline differences in PCS may have led
to overadjustment because of baseline PCS being on the
causal pathway between graded neck pain and 6-month
PCS [37]. Baseline PCS may mediate the association between
baseline graded neck pain and 6-month PCS based
on the measures used. Baseline graded neck pain was measured
in the CPQ by asking seven questions; six of the questions
asked about neck pain in the last 6 months. In the
SF-36 PCS, questions relate to HRQoL at present and over
the previous 4 weeks. If baseline PCS is a mediator, then it
should not be adjusted for confounding influences. On the
other hand, not controlling for baseline differences in
PCS may cause us to overestimate our results if there is little
mediation of the association. The true association likely
lies somewhere between the final model including baseline
PCS and the final model without baseline PCS.
Neck pain was the independent variable used in the multiple
linear regression models of this study and includes
everyone answering the baseline CPQ question on neck
pain. Because we did not start with a population at risk
of developing neck pain (incidence study), it was important
to look at the course or trajectories of neck pain between
the baseline and the 6-month survey. There was a crude association
between the neck pain trajectories and both PCS
and MCS scores at 6 months. PCS and/or MCS scores at
baseline also predicted the course of neck pain in crude
analyses. It is possible that HRQoL could be both a mediator
and confounder of this association. Neck pain trajectories
were also examined for changes in PCS and MCS
scores over the 6 months of the study. The neck pain trajectory
with persistent troublesome neck pain and the trajectory
with worsening neck pain had worsening PCS
change scores over the 6 months of the study (4.3 and 6.8
points, respectively). No changes in PCS scores were seen
in the neck pain trajectory that improved over 6 months. It
is possible that PCS HRQoL gets worse with the onset of
neck pain and continues to get worse in subjects with ongoing
persistent neck pain. Once neck pain improves, it
may take a longer period of time to see improvements in
physical HRQoL.
Our study has limitations. First, 55% of the invited study
population participated in the survey. Therefore, it is possible
that our results were influenced by selection bias. However,
we are confident that our exposure was representative
of the distribution in the study population [2]. Moreover, a
previous analysis by Rezai et al. [8] suggests that missing
baseline data did not lead to bias in this dataset. Second,
it is possible that selection bias was introduced through loss
to follow-up. Nonresponders to the 6-month follow-up survey
questionnaire were younger, less educated, and had
lower income than responders. However, their baseline
PCS and MCS scores were similar, which suggest that attrition
was not because of baseline HRQoL. Third, the SF-36
is known to be more responsive to lumbar spine and lower
extremity function than to the upper extremity and the cervical
spine function [7]. Therefore, the instrument may not
have fully captured the impact of neck pain on physical
HRQoL. Finally, our analysis of the MCS scores may have
been overadjusted for depressive symptomatology, which
may be both a mediator and a confounder of the association
between neck pain and HRQoL [34]. As mentioned previously,
viewing depressive symptomatology as a confounder
of the association between neck pain and HRQoL may have
led to an underestimation of the true effect.
Our results indicate that neck pain can affect the future
physical health-related quality of life (HRQoL) of individuals. This impact was worse in
individuals with worsening or persistent neck pain. These
results emphasize the importance for health-care providers
and policy makers to manage neck pain with early effective
interventions to minimize the long-term impact on physical
HRQoL. Future research needs to examine the course of
neck pain on HRQoL while controlling for the confounding
effects of socioeconomic, lifestyle, and comorbidities. Further
research is also needed to examine the mediating and
confounding effects of depression on the association between
neck pain and mental HRQoL.
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