PLoS One. 2014; 9(5): e97134.
Published online 2014 May 21. doi: 10.1371/journal.pone.0097134
PMCID: PMC4029603
Ruth Landau, Editor
This article has been cited by other articles in PMC.
Abstract
Background
There
is a lack of research about a potential education-related bias in
assessment of patients with chronic pain. The aim of this study was to
analyze whether low-educated men and women with chronic pain were less
often selected to multidisciplinary rehabilitation than those with high
education.
Methods
The
population consisted of consecutive patients (n = 595 women, 266 men)
referred during a three-year period from mainly primary health care
centers for a multidisciplinary team assessment at a pain rehabilitation
clinic at a university hospital in Northern Sweden. Patient data were
collected from the Swedish Quality Registry for Pain Rehabilitation
National Pain Register. The outcome variable was being selected by the
multidisciplinary team assessment to a multidisciplinary rehabilitation
program. The independent variables were: sex, age, born outside Sweden,
education, pain severity as well as the hospital, anxiety and depression
scale (HADS).
Results
Low-educated
women were less often selected to multidisciplinary rehabilitation
programs than high-educated women (OR 0.55, CI 0.30–0.98), even after
control for age, being born outside Sweden, pain intensity and HADS. No
significant findings were found when comparing the results between high-
and low-educated men.
Conclusion
Our
findings can be interpreted as possible discrimination against
low-educated women with chronic pain in hospital referrals to pain
rehabilitation. There is a need for more gender-theoretical research
emphasizing the importance of taking several power dimensions into
account when analyzing possible bias in health care.
Introduction
A
large number of studies indicate that there is a gender bias to women's
disadvantage, i.e. an unintended and systematic neglect of women, in
health care [1], [2]. Most of this research has been performed on coronary heart disease [3], but also in relation to other symptoms and diagnoses [1], [4]–[6].
For example, the so-called “laundry bag project” (LBP) discovered
gendered standards for dermatological treatment of common diagnoses. The
study included gender-based quantitative analysis of treatment of all
patients (n = 320 women, 421 men) referred to a dermatological clinic.
The study showed that men with diagnoses of psoriasis or eczema received
more whole-body UV treatment and more help with emollients than did
women [5].
In economic terms, women patients subsidized the treatment budget of
the clinic to a value of 22 per cent. In similar ways, medically
unjustified differences in the availability of examination and treatment
for women compared to men have been demonstrated in connection with a
number of other diseases, such as irritable bowel syndrome [1], renal transplantation, HIV and pain [6], [7].
Gender bias in neck pain was found when Swedish interns were asked
about the diagnosis and management of this group of patients.
Non-specific somatic diagnoses, psychosocial questions, drug
prescriptions and the expressed need of diagnostic support from a
physiotherapist and an orthopedist were more commonly proposed for women
than for men [7].
Gender bias may also mean that men are disadvantaged in health care [8], which has been discussed for example in relation to the treatment of depression [9] and osteoporosis [10]
in older men. In these cases, diagnostic models have been developed for
women while criteria to identify risk in men are not well established. A
case study of osteoporosis from Gendered Innovations [10]
has developed male reference populations and identified medical
conditions (especially among men) that are related to osteoporotic
fracture, allowing for better evaluation of fracture risk in men. In
addition, among patients with chronic pain, women participate in
multidisciplinary rehabilitation programs (which are a combination of
different physical and psychological interventions that is linked to
teamwork) more often than men, and some studies have demonstrated that
women benefit more from this kind of rehabilitation than men do [11].
Systematic reviews of treatment and rehabilitation of patients with
chronic pain have shown evidence that multidisciplinary rehabilitation
programs have superior effects on multidimensional outcomes compared to
less intensive treatments [12]–[14].
However, most of the reviews do not analyze differences in treatment
among men as compared to women. Thus, the question remains to study
whether there is a gender bias in the treatment of chronic pain.
Increasingly
important has been to analyze not only gender, but to include multiple
power dimensions in the analyzes of gender bias such as socioeconomic
status, ethnicity and age. For example in Swedish health care, research
on gender bias has shown that it is not women as a group but older,
low-educated women who have worse outcome in stroke care [15].
However, overall rather few studies have been performed within this
field of intersectional gender research. To the best of our knowledge
there is no research analyzing whether or not low-educated women (and
men) of various ages with chronic pain are less frequently selected for
multidisciplinary rehabilitation compared to high-educated.
The
aim of this study was therefore to analyze whether low-educated men and
women with chronic pain were less often selected for multidisciplinary
rehabilitation than those with high education.
Methods
Ethical statement
The
study was approved by the Regional Ethics Vetting Board in Umeå,
Sweden. Informed consent was not required because we only handled
unidentified register data. According to Swedish law (Swedish Ethical
Review Act 2003;460, §§ 20–21, Swedish Personal Data Law 1998:204 § 19)
informed consent is not required when dealing with unidentified register
data (as was the case in our study).
Setting
The
study was conducted in a clinical setting at the Pain Rehabilitation
Clinic at Umeå University Hospital, Sweden. In order for a referred
patient to be selected for assessment at the clinic the patients had to
have a chronic disabling non-malignant diagnosis of chronic pain.
Patients with serious somatic diagnoses (such as cancer, rheumatoid
arthritis and neurological disorders that should be investigated by
other specialist clinics) are excluded. The most frequent diagnostic
groups at the clinic are columnar pain (50%) followed by extremity pain
(18%) [16].
The
selected patients were assessed during two days at the pain
rehabilitation clinic by multidisciplinary diagnostic teams consisting
of a specialist physician in rehabilitation medicine, a physiotherapist,
a social worker, an occupational therapist and a psychologist if
needed. If the multidisciplinary teams assessed that the patient was in
need of multidisciplinary rehabilitation and fulfilled the inclusion
criteria (described below), they were selected to participate in a
rehabilitation program based on a bio-psychosocial model with cognitive
behavioural principles [16].
The multidisciplinary rehabilitation program focused on pain management
and education about pain and its consequences. Rehabilitation was based
on collaboration within the multidisciplinary team with the patient as
an active team member. The patient was expected to participate with the
team in goal setting and reaching the decided goals. A number of core
sessions were conducted, e.g. physiotherapy (swimming pool exercise and
relaxation exercises), ergonomics, education about pain mechanisms and
coping with pain. At the end of the program contact was established with
the patient's primary care physician.
Inclusion criteria for referral to the multidisciplinary rehabilitation program were (i)
disabling non-malignant chronic and complex musculoskeletal pain (on
sick leave or experiencing major interference in daily life due to
chronic pain); (ii) age 18–65 years; (iii) no further medical investigations needed; (iv) written consent to participate in and attend the multidisciplinary program; (v)
agreement not to have parallel contacts with therapists such as
physiotherapists while attending the multidisciplinary pain
rehabilitation program.
Population
The
population consisted of consecutive patients (n = 595 women, 266 men)
referred mainly from primary health care centers to the pain
rehabilitation clinic and assessed between 5 November 2007 and 13
December 2010.
Design and data collection
Patient data were collected from the Swedish Quality Registry for Pain Rehabilitation National Pain Register (SQRP) [17]
and linked to the patients' individual records containing the final
decision on being selected or not to multidisciplinary rehabilitation
programs. The SQRP register has aggregated data since 1998 of all
patients referred to the majority of Swedish rehabilitation units. The
SQRP is based on patients' information from validated self-administered
questionnaires completed before the first multidisciplinary assessment [17].
The patients completed the set of questionnaires at home the night
before the assessment and the questions refer to pain experiences during
the day before the assessment. The questionnaires were handed in on the
day of assessment and were subsequently registered in SQRP.
Outcome variable
The
outcome variable was being selected ( = 1) for a multidisciplinary
rehabilitation program as compared to not being selected ( = 0).
Independent variables
The
following independent variables were used: sex, age (used as a
continuous variable) and country of birth (Sweden, other Nordic country,
Europe (except Nordic countries) and other country) recoded as born
outside of Sweden = 1, born in Sweden = 0. Education was measured with
the following question: Which is your highest completed level of
education? The following four answer alternatives were given: 1. Nine
years of compulsory school, 2. Two- or three-year secondary high school
(including both theoretical programs and vocational training), 3.
University studies 4. Other education (which could mean in-service
training supported by a company or organization, folk high school etc.).
Low-educated was defined as having completed compulsory school ( = 1)
as compared to all other completed forms of education.
To
adjust for depression and anxiety, the often used and validated 14-item
self-reported HADS (Hospital, anxiety and depression) scale was used [18].
Due to high correlation between the anxiety and the depression scale,
the two scales were combined into a continuous variable with a total
range of 0–42 [19].
In the multivariate logistic regression analyzes, low HADS equals 0.The
HADS has proven to be reliable and valid when used to assess symptom
severity in anxiety and depression among somatic, psychiatric and
primary care patients [20].
Pain
severity was used as a continuous variable (range 0–6) based on a
subscale from the Multidimensional Pain Inventory (MPI), Part I [21], [22].
In the multivariate logistic regression analyzes, low pain severity
equals 0. The MPI has demonstrated good reliability and validity for
patients with chronic pain [23].
Statistical analysis
The
associations between low education and referral to multidisciplinary
rehabilitation programs were investigated for men and women separately
by means of multivariate logistic regression analyzes, using SPSS
statistical package (SPSS version 18 for Windows). The first model
(Model 0) consisted of bivariate associations. The following models were
age-adjusted. Model 1 included the variable ‘born outside Sweden’ while
model 2 also included HADS and pain severity. As significance tests we
used chi-square for dichotomous variables and t-test for continuous
variables. The correlation between the confounders was <0.3.
Availability of data
The
SQRP is a national quality registry supported by the Swedish
Association of the Local Authorities and Regions and connected to the
Uppsala Clinical Research Center (UCR). Our dataset has great potential
for secondary analysis. The data are not freely available but
collaborative ideas are welcome. Britt-Marie Stålnacke is the contact
person. The website with documentation for the SQRP and detailed
information about variables is available at http://www.ucr.uu/nrs/.
Results
The distribution of the dependent and independent variables for men and women are shown in Tables 1 and and22.
Prevalence of dichotomous covariates among women and men, n = 861 (per cent).
Prevalence of continuous covariates between women and men, n = 861 (mean (SD)).
The
tables show that significantly more women than men were selected for
multidisciplinary rehabilitation. More men than women were born abroad.
For the other variables, no significant differences between men and
women were found. Around 15 per cent were low-educated.
Table 3
shows the logistic regression analyzes in four age-adjusted models for
men and women separately with referral to multidisciplinary
rehabilitation programs as outcome.
Logistic
regression analyzes for referral to multidisciplinary rehabilitation
program among women and men in relation to low education
(reference = high education) and other independent variables.
The
table shows that low-educated women were less often selected for
multidisciplinary rehabilitation programs as compared to high-educated
women. The odds ratios for low education were significant in all models
and did not particularly attenuate in the fully adjusted model (from
0.53 in the univariate to 0.55 in the last model). Among men, there were
no significant odds ratios between low education and referral to
multidisciplinary rehabilitation programs in any of the models. But the
odds ratios pointed in the same direction as among women. None of the
other independent variables were significantly related to
multidisciplinary rehabilitation among men or women.
Discussion
This
study aimed to analyze whether low-educated men and women with chronic
pain were less often selected for multidisciplinary rehabilitation
compared to high-educated. We found that low-educated women were less
often selected for multidisciplinary rehabilitation programs than
high-educated women and that this relationship remained almost unchanged
after control for all the covariates (including pain intensity and
mental illness).
A possible explanation to these
findings may be that women with lower levels of education might be less
likely to fulfil the inclusion criteria. Women might for example be more
likely to need further medical investigations or be less likely to
agree to give up their contacts with other. However, neither
low-educated nor women were overrepresented among those who needed
further medical investigation (data not shown). In addition, almost
everyone who was selected to the multidisciplinary rehabilitation
programs agreed to participate. Thus, the fact that low-educated women
were not referred to multidisciplinary rehabilitation as often as
high-educated women cannot be explained by such factors.
Overall,
there is a lack of international studies about possible bias in
referral of low-educated patients to pain rehabilitation. However, our
findings are in line with a broader scope of research, demonstrating
socioeconomic bias in specialist health care [24]–[28].
A comprehensive study of health care utilization in 12 EU member states
found consistent evidence that the wealthy and/or high-educated were
more likely to have contact with medical specialists than the poor and
low-educated [28].
Moreover, selection for cardiac rehabilitation has been found to favor
participants with good prognosis and disfavor patients from deprived
areas who tend to have poorer prognosis [24], [26].
Also waiting time for carotid surgery after stroke was significantly
longer for low-income patients compared with high-income patients [27], [29]. However, gender differences were not analyzed in these studies.
The
current finding that low-educated women with chronic musculoskeletal
pain were less often selected for multidisciplinary rehabilitation
programs is surprising for several reasons. First, consistent findings
point to socioeconomic indicators, such as educational level, as strong
predictors of musculoskeletal disorders and reporting of chronic pain
conditions in both men and women [30]–[34].
MacFarlaine et al. found that low socioeconomic status in adulthood was
associated with major regional musculoskeletal pain and chronic
widespread pain [32].
Individuals in the lowest socioeconomic class had a three-fold
increased risk of widespread pain, and the impact of childhood
socioeconomic status was less prominent than adult socioeconomic status [32].
In addition Overland et al. found that individuals with widespread
musculoskeletal pain were characterized by being women, having lower
education/lower household income, poor general health including higher
prevalence of common mental disorders and higher risk for future
disability pension [35].
Based on these findings one should expect that lower educated women and
men with chronic musculoskeletal pain conditions were at least equally
prioritized with respect to multidisciplinary treatment at specialized
rehabilitation clinics [36].
Second,
our findings demonstrated a limited impact of age, being born outside
Sweden, pain intensity and mental illness on the relation between
education and being selected for rehabilitation programs. These findings
indicate that gender bias may be at stake and that the combination of
gender and education play a significant role when deciding who is
suitable for multidisciplinary rehabilitation.
Third,
Sweden is a country well-known for its historical political engagement
for achieving increased equality in society. According to Swedish law,
the overall goal for health care is that it should be given on equal
terms for the whole population [36].
Our findings point in the direction of discrimination against
low-educated women in the rehabilitation of chronic pain which is not in
accordance with the Swedish law.
More women than men
were referred to rehabilitation. An explanation could be simply the fact
that the prevalence of pain is higher in women than men [37], [38].
Another explanation could be that men with pain are more often referred
to specialist treatment and therefore get more precise diagnoses and
treatment than women [7].
However, the patients in our register were assessed at a specialist
clinic. Our findings cannot be interpreted as a gender bias against men
because we do not know the clinical reasons behind these findings.
In
general, our findings are in line with gender-theoretical research
emphasizing the importance of taking several power dimensions into
account when analyzing possible bias in treatment [39], [40].
Thus, our findings draw attention to the importance of not viewing men
and women as static groups but analyzing differences within (and
similarities across) the group of men and women. Intersectional
approaches mean that dimensions of inequalities do not simply
accumulate. Instead one category such as ‘low education’ takes its
meaning from another such as ‘gender’ and new hybrids develop as these
categories are new hybrid structures which emerge at the intersections
of inequality [41].
Qualitative methods could preferably be used in order to understand the
meaning of such hybrids in pain rehabilitation. Thus, there is a need
for more intersectional research about what happens in the meeting
between patients and care-givers. In this study, we have no such
measures.
Limitations and strengths
The
current study is based on register data which has some limitations.
Above we discuss that our findings point in the direction of
discrimination of low-educated women. Discrimination can be seen to
exist if high and low educated women have the same health needs but
receive different treatment. However, the lack of certain social and
clinical variables in the SQRP register about health needs prohibits us
from drawing firm conclusions about discrimination. Even though we
assume that rehabilitation is the best treatment for the patients
referred to the pain rehabilitation clinic, it could be the case that
the evaluating teams concluded that the low educated women would not
benefit from the programs due to for example manual workload, domestic
strain and less possibility to rest. But none of these circumstances are
considered contra-indicative of multidisciplinary rehabilitation, and
should not be relevant when decisions are taken by multidisciplinary
teams. As the rehabilitation programs take into account the individual
needs of the patients and support them to set their own goals, we have
no reason to believe that the needs of lower educated women are not
attended to in the assessment. Since the physicians examine patients by
standard procedures we do not believe that mis-diagnosis in women with
low education is a problem.
Due to the limitations of
the register data we do not have information on diagnoses of diseases
causing the pain. However, in a previous study from the pain
rehabilitation clinic (with access to diagnoses) no significant
differences were found in diagnostic groups between patients being
selected for multidisciplinary rehabilitation compared to all assessed
patients [16].
In addition, there are strict selection criteria for the pain
rehabilitation clinic in our study, which means that in order to get an
initial appointment at the clinic, the patients must have a disabling
non-malignant diagnosis of chronic pain and that other diagnoses (such
as cancer, rheumatoid arthritis, neurological disorders) are excluded.
Co-morbidity
could be the basis of different therapeutic efforts in patients with
different levels of education. Our register contained information about
the most important comorbid conditions, which are depression and anxiety
[43], [44].
We have performed sensitivity analyzes with clinical cut-off points for
depression and for anxiety (with case level >10 in HADS). The
inclusion of the clinical cut-off points for depression and anxiety
separately did not change the overall findings. But a limitation is that
we do not have information about other comorbidity, for example
post-traumatic stress symptoms and fear avoidance. Earlier research
shows no socioeconomic differences in post-traumatic stress symptoms [42].
Comorbid symptoms of fear avoidance are not contra-indicative of
multidisciplinary pain rehabilitation and are dealt with in
rehabilitation programs. A minority of the patients referred to the Pain
Rehabilitation Clinic suffered from other physical diseases and were
referred to other clinics. As this is a very small group we have no
reason to believe that low-educated women are over-represented among
them.
Due to these methodological uncertainties, we
interpret our findings as a possible (in contrast to a confirmed)
discrimination against low-educated women. There is a need for more
empirical research about the topic with studies which have more clinical
data as well as more information about the decision making process.
More
women than men were referred to the rehabilitation clinic. Therefore,
lack of significant findings between educational level and selection for
multidisciplinary rehabilitation among men may be due to a type
2-error. Use of an already established registry (SQORP) for measures of
socio-demographic data and pain indicators restricted the possibility of
including other measures of interest. On the other hand, the measures
included are validated and have been widely used in clinical practice
for assessment of pain severity, anxiety and depression.
Low
education was defined as not having education beyond compulsory school,
but what is ‘low’ can always be discussed. Sensitivity analyzes were
performed with other dichotomizations,such as no education beyond
secondary high school, which showed similar results. Therefore, we chose
to use the lowest level of educational attainment.
The
main strength of the present study is the relatively high number of
patients included and that recruitment of participants was restricted to
one specific rehabilitation clinic. During the three-year inclusion
period, the procedures for multidisciplinary team assessments did not
change, thus enhancing the reliability of the data. In addition the team
assessment was performed by experienced professionals with high staff
continuity during the data collection period. Further, SQRP is a
national register for pain rehabilitation and includes approximately 80%
of pain management programs in Sweden [17].
The procedure used by the multidisciplinary team for selection of
patients for multidisciplinary rehabilitation is similar throughout
Sweden; thus, we can assume that the generalisability of the study is
good on a national level.
Moreover, since comparable
multidisciplinary assessment and selection visits often precede
participation in rehabilitation programs in other counties as well [16],
and since the MPI and HADS questionnaires have been widely used for
measuring chronic pain, depression and anxiety in a range of pain
rehabilitation contexts [20],
we can assume that the generalisability of the study is good to
countries with similar organization for the rehabilitation of patients
with chronic pain.
Our outcome measure takes account of
both diagnostic (International Classification of Diseases, 10th version
(ICD-10)) and functional (International Classification of Disability,
Impairment and Handicap (ICIDH)) components [17]. The SQRP consists of validated scales [20], [21].
Selection criteria and assessment procedures for multidisciplinary
rehabilitation are relatively similar across countries that offer
organized treatment of patients with chronic pain [16]; thus, we can assume that the external validity of the study is relatively good.
In
this study general practitioners referred the patients to a specialist
pain rehabilitation clinic. Thus, the patients represent a selected
group with a more complex chronic pain condition than patients treated
in primary care. More research on this topic is needed in other contexts
– both other clinical contexts and various geographical locations.
Conclusions
Our
findings can be interpreted as possible discrimination against
low-educated women with chronic pain in hospital referrals to
multidisciplinary pain rehabilitation. More research is needed to
analyze whether such discrimination also occurs in other clinical
settings. There is a need for more gender-theoretical research
emphasizing the importance of taking several power dimensions into
account when analyzing possible bias in treatment.
Acknowledgments
The authors would like to thank Vanja Nyberg and Ylva Persson for valuable assistance in collecting the data.
Funding Statement
This work was supported by the Swedish Research Council (grant no: 344-2009-5839). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.References
1. Risberg
G (2004) “I am solely a professional – neutral and genderless”: on
gender bias and gender awareness in the medical profession
[Dissertation]: Umeå University.
2. Ruiz-Cantero MT, Vives-Cases C, Artazcoz L, Delgado A, Garcia Calvente MM, et al. (2007) A framework to analyse gender bias in epidemiological research. J Epidemiol Community Health 61 Suppl 2ii46–53 [PMC free article] [PubMed]
3. Bosner S, Haasenritter J, Hani MA, Keller H, Sonnichsen AC, et al. (2011) Gender bias revisited: new insights on the differential management of chest pain. BMC Fam Pract 12: 45. [PMC free article] [PubMed]
4. Borkhoff CM, Hawker GA, Kreder HJ, Glazier RH, Mahomed NN, et al. (2008) The effect of patients' sex on physicians' recommendations for total knee arthroplasty. CMAJ 178: 681–687 [PMC free article] [PubMed]
5. Nyberg F, Osika I, Evengård B (2008) “The
Laundry Bag Project” – unequal distribution of dermatological
healthcare resources for male and female psoriatic patients in Sweden. Int J Dermatol 47: 144–149 [PubMed]
6. Raine R (2000) Does gender bias exist in the use of specialist health care? J Health Serv Res Policy 5: 237–249 [PubMed]
7. Hamberg K, Risberg G, Johansson EE, Westman G (2002) Gender bias in physicians' management of neck pain: a study of the answers in a Swedish national examination. J Womens Health Gend Based Med 11: 653–666 [PubMed]
8. Noone JH, Stephens C (2008) Men, masculine identities, and health care utilisation. Sociol Health Illn 30: 711–725 [PubMed]
9. Apesoa-Varano EC, Hinton L, Barker JC, Unützer J (2010) Clinician Approaches and Strategies for Engaging Older Men in Depression Care. Am J Geriatr Psychiatry 18: 586–595 [PMC free article] [PubMed]
10. Gendered Innovation's homepage. Available: http://genderedinnovations.stanford.edu/ Accessed 14 January 2014.
11. Jensen IB, Bergström G, Ljungquist T, Bodin L (2005) A 3-year follow-up of a multidisciplinary rehabilitation program for back and neck pain. Pain 115: 273–283 [PubMed]
12. SBU (2010) Chronic Pain Rehabilitation. Stockholm: Swedish Council of Health Technology Assessment.
13. SBU
(2006) Methods for treatment of chronic pain. Stockholm: The Swedish
Council on Technology Assessment in Health Care. Report No.177.
14. Scascighini L, Toma V, Dober-Spielmann S, Sprott H (2008) Multidisciplinary treatment for chronic pain: a systematic review of interventions and outcomes. Rheumatology (Oxford) 47: 670–678 [PubMed]
15. Löfmark U, Hammarström A (2007) Evidence
for age-dependent education-related differences in men and women with
first-ever stroke. Results from a community-based incidence study in
northern Sweden. Neuroepidemiology 28: 135–141 [PubMed]
16. Merrick D, Sundelin G, Stålnacke BM (2012) One-year follow-up of two different rehabilitation strategies for patients with chronic pain. J Rehabil Med 44: 764–773 [PubMed]
17. Nyberg V, Sanne H, Sjölund BH (2011) Swedish quality registry for pain rehabilitation: purpose, design, implementation and characteristics of referred patients. J Rehabil Med 43: 50–57 [PubMed]
18. Zigmond AS, Snaith RP (1983) The hospital anxiety and depression scale. Acta Psychiatr Scand 67: 361–370 [PubMed]
19. Cosco TD, Doyle F, Ward M, McGee H (2012) Latent structure of the Hospital Anxiety and Depression Scale: a 10-year systematic review. J Psychosom Res 72: 180–184 [PubMed]
20. Bjelland I, Dahl AA, Haug TT, Neckelmann D (2002) The validity of the Hospital Anxiety and Depression Scale. An updated literature review. J Psychosom Res 52: 69–77 [PubMed]
21. Kerns RD, Turk DC, Rudy TE (1985) The West Haven-Yale Multidimensional Pain Inventory (WHYMPI). Pain 23: 345–356 [PubMed]
22. Pietila Holmer E, Fahlström M, Nordström A (2013) The effects of interdisciplinary team assessment and a rehabilitation program for patients with chronic pain. Am J Phys Med Rehabil 92: 77–83 [PubMed]
23. Dworkin RH, Turk DC, Farrar JT, Haythornthwaite JA, Jensen MP, et al. (2005) Core outcome measures for chronic pain clinical trials: IMMPACT recommendations. Pain 113: 9–19 [PubMed]
24. Beswick AD, Rees K, West RR, Taylor FC, Burke M, et al. (2005) Improving uptake and adherence in cardiac rehabilitation: literature review. J Adv Nurs 49: 538–555 [PubMed]
25. Carr JL, Moffett JA (2005) The impact of social deprivation on chronic back pain outcomes. Chronic Illn 1: 121–129 [PubMed]
26. Melville MR, Packham C, Brown N, Weston C, Gray D (1999) Cardiac
rehabilitation: socially deprived patients are less likely to attend
but patients ineligible for thrombolysis are less likely to be invited. Heart 82: 373–377 [PMC free article] [PubMed]
27. van den Bos GA, Smits JP, Westert GP, van Straten A (2002) Socioeconomic variations in the course of stroke: unequal health outcomes, equal care? J Epidemiol Community Health 56: 943–948 [PMC free article] [PubMed]
28. van Doorslaer E, Masseria C, Koolman X (2006) Inequalities in access to medical care by income in developed countries. CMAJ 174: 177–183 [PMC free article] [PubMed]
29. Kapral MK, Wang H, Mamdani M, Tu JV (2002) Effect of socioeconomic status on treatment and mortality after stroke. Stroke 33: 268–273 [PubMed]
30. Björnsdottir SV, Jonsson SH, Valdimarsdottir UA (2013) Functional limitations and physical symptoms of individuals with chronic pain. Scand J Rheumatol 42: 59–70 [PubMed]
31. Friedrich M, Hahne J, Wepner F (2009) A
controlled examination of medical and psychosocial factors associated
with low back pain in combination with widespread musculoskeletal pain. Phys Ther 89: 786–803 [PubMed]
32. Macfarlane GJ, Norrie G, Atherton K, Power C, Jones GT (2009) The
influence of socioeconomic status on the reporting of regional and
widespread musculoskeletal pain: results from the 1958 British Birth
Cohort Study. Ann Rheum Dis 68: 1591–1595 [PubMed]
33. Perruccio AV, Gandhi R, Rampersaud YR (2013) Heterogeneity
in health status and the influence of patient characteristics across
patients seeking musculoskeletal orthopaedic care – a cross-sectional
study. BMC Musculoskelet Disord 14: 83. [PMC free article] [PubMed]
34. Toivanen S (2011) Exploring
the interplay between work stress and socioeconomic position in
relation to common health complaints: the role of interaction. Am J Ind Med 54: 780–790 [PubMed]
35. Overland S, Harvey SB, Knudsen AK, Mykletun A, Hotopf M (2012) Widespread pain and medically certified disability pension in the Hordaland Health Study. Eur J Pain 16: 611–620 [PubMed]
36. Health and Medical Services Act [Hälso- och sjukvårdslagen] SFS (1982) 763
37. Winjhoven HA, deVet HC, Picavet HC (2006) Prevalence of musculoskeletal disorders is systematically higher in women than in men. Clin J Pain 22: 717–24 [PubMed]
38. Stubbs D, Krebs E, Bair M, Damush T, Wu J, et al. (2010) Sex-differences in pain and pain related disability among primary care patients with chronic musculoskeletal pain. Pain Med 11: 232–9 [PubMed]
39. Hankivsky O (2012) Women's health, men's health, and gender and health: implications of intersectionality. Soc Sci Med 74: 1712–1720 [PubMed]
40. Springer KW, Hankivsky O, Bates LM (2012) Gender and health: relational, intersectional, and biosocial approaches. Soc Sci Med 74: 1661–1666 [PubMed]
41. Shields S (2008) Gender: An intersectionality perspective. Sex Roles 59: 301–311
42. Boman KK, Kjällander Y, Eksborg S, Becker J (2013) Impact of prior traumatic life events on parental early stage reactions following a child's cancer. PLoS One 8(3): e57556. [PMC free article] [PubMed]
43. Bair MJ, Robinson RL, Katon W, Kroenke K (2003) Depression and pain comorbidity: a literature review. Arch Intern Med 163: 2433–2445 [PubMed]
44. Jordan KD, Okifuji A (2011) Anxiety disorders: differential diagnosis and their relationship to chronic pain. J Pain Palliat Care Pharmacother 25: 231–245 [PubMed]
Articles from PLoS ONE are provided here courtesy of Public Library of Science
