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50 Mary CARDOSA, Phoon Ping CHEN
[29]. In fact, epidemiology research can also allow
the study of the distribution of chronic pain and
identify the determinants of the condition and its
effects across the different groups. Only then we
may develop appropriate management strategies to
prevent and control this menace. An example of
questions asked in an epidemiological study of low
back pain is shown in Table 5.01.
Epidemiological study designs
e scope of this chapter does not allow for detailed
discussion of epidemiological research methods, and
only a basic understanding of common methods
is presented here. ere are generally two types
and observational designs [68]. In an experimental
design, the subject is purposely exposed to the
possible risk factor and is followed up over time
to detect the effect of the exposure. A clinical
trial of a treatment that introduces the treatment
being studied randomly to subjects who have the
health condition being treated is an example of
experimental design. In an observational study,
samples are drawn from the general population
without reference to the health condition being
studied or risk-factor status. e exposure and
outcome status of each subject are then observed
and examined. e most commonly used methods
in epidemiology are observational studies.
Surveys are commonly used to study chronic pain.
ese are usually cross-sectional observational
studies that investigate the relationship of chronic
pain conditions and factors of interest in a specified
population at a particular point of time. A single
cross-sectional survey is useful for estimation
of prevalence of the chronic pain condition
and provides information on its distribution by
sociodemographic characteristics. It also allows
some inference into the relationship between risk
factors such as work-related injury, compensation
and chronic pain. However, it is not possible to
establish a causal relationship from the study or
learn about the natural history of the low back pain
from a cross-sectional survey. When subjects in
an initial survey are followed over time, the study
becomes a longitudinal study.
Chronic pain surveys have been conducted on
the general population [8, 85], patients registered
at general practices [38] and pain clinics [20],
populations of a particular pain diagnosis such as
back pain [70], neuropathic pain [116] or orofacial
pain [77], different occupational groups [51], in
older adults [113] and children [90, 96], and on
samples in different geographical locations [3, 13].
Many surveys have also focused on different issues
including prevalence [30, 85], external factors
that influence the severity and impact of the pain
condition [10], psychological determinants [14,
15] and impact on individuals and society [9, 64]
including economic cost [75].
Two other common epidemiological research
designs are the cohort study and case-control study.
In the cohort study, the subjects are categorised
on the basis of their exposure and then observed
over time to see if they develop the chronic pain
condition being studied. For example, patients
who presented with acute nonspecific low back
pain were prescribed bed rest, back exercises or
continuation of their normal activities, and then
followed up over time to see if they developed
chronic low back pain [74]. It is important to note
that bias from loss to follow-up, missing data and
unreliable measurements in longitudinal study may
affect the outcome measurement of the condition
being studied. Although conceptually quite similar,
a cohort study differs from an experimental design
in that the exposure status in the cohort study is
observed rather than determined by the study. A
cohort study also differs from a repeated cross-
sectional survey in that the former studies the same
group of individuals who participated over a period
of time, whereas the latter is usually conducted in
different study sample.
Table 5.01 Questions of interest in the
epidemiology of low back pain
1. Who are those people who have low
back pain — their age, gender, ethnicity,
occupation, socioeconomic status, etc.?
2. What is the scale of the problem — how many
people have the condition?
3. What is the impact of the low back pain on the
people who have it?
4. When did they develop low back pain?
5. How did they acquire the low back pain?
6. Where did they acquire the low back pain?
7. Why do they get low back pain — what is the
cause?
8. What factors can influence the condition and
its effect?
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51
Epidemiology in Chronic Pain, Gender and Cultural Aspects
In a case-control study, a group of subjects with
the pain condition is compared against a relevant
control group, i.e. without the pain condition, to
examine their patterns of exposure and to compare
their impacts on the pain condition. Case-control
studies may be used to estimate the odds ratio for risk
factors being studied. One of the main difficulties
in this method is the selection of a suitable and
most relevant control group. ere are a number of
potential sources of bias that may affect case-control
study and caution is necessary in the interpretation
of its results. Some examples of these biases include
referral bias, which occurs when the referral patterns
cause an over- or under-representation of exposed
cases in the study population, ascertainment bias
that occurs when there is inaccurate confirmation
of either the disease or exposure and admission
rate (Berkson) bias that tends to overestimate the
exposed cases in a hospital population (in patients
with more than one disease, as they are more likely
to be hospitalised than patients with one disease)
[111].
In epidemiological studies, it is very important to
define clearly the particular disease and any factors
that are being investigated. e definition of a
chronic pain condition may affect the prevalence
estimate [125]. As an example, a recent study
reviewed two large Canadian population-based
surveys that studied the prevalence of pain using
two different sets of questions. When the studies
were closely examined, they reported that the actual
overall prevalence of self-reported pain was 39%
for 1-week pain, 66% for 4-week pain and 15%
for chronic pain [122]. A standard definition with
a set of standard criteria will ensure that all cases are
diagnosed in the same way regardless of who makes
the diagnosis, or when or where it occurs, and will
facilitate the comparison of data at different time
and place. Similarly, a standardised methodology
in epidemiological research is also important
when evaluating similar conditions or risk factors.
Otherwise, results will be difficult to repeat and
compare [71]. In samples where the definition of
pain duration is different, different risk factors and
profiles will apply to the different groups.
Epidemiological studies must also be conducted on
representative samples of the population in order
for the findings to have any meaningful and valid
generalisation to the respective population groups.
A review of epidemiological studies on chronic
pain has been reported previously [125]. Detailed
discussion of sampling techniques and sample
size estimation are described in relevant statistical
references.
Application of epidemiology in
pain medicine
Pain medicine is a relatively new discipline. While
pain in some countries may be considered a disease
in its own right [104], in most of the developing
world, pain is still considered a symptom of
some other medical conditions and is treated as
such. Epidemiology research has an important
role to play in highlighting the extent of the pain
problem and in convincing health administrators
to consider appropriate health service planning and
prioritisation of resources in pain management.
Recent epidemiological data have demonstrated
that chronic pain is prevalent in our community
and represents a major economic burden to our
society in terms of high health care utilisation [7,
9], reduced productivity [10, 123], and significant
legal costs, social welfare [8] and work-injury
compensation claims [11, 20]. In addition, there are
also significant psychological and social sufferings,
pain-related disability, impairment in quality of life
and physical functions in individuals with chronic
pain [5, 9, 13, 21, 45, 64, 80, 106].
Epidemiology also has a role in determining the
cause of different pain conditions and factors
(including risk factors) affecting them. Recent
research has indicated that gender and cultural
differences may account for some of the differences
in pain experience among different groups [61, 66].
Other factors such as psychological “yellow flags”
and inadequate coping strategies may contribute to
greater risk of disability in chronic pain [52, 60,
69]. is knowledge allows clinicians to devise and
implement preventative strategies to reduce the
risk of chronic disability and management plans to
optimise the ability of chronic pain sufferers to live
an active quality life.
By determining the pattern of chronic-pain
clinical presentations, epidemiological studies
also facilitate the identification of different pain
diagnostic groups and how they may differ in their
relationships with different psychological factors,
social circumstances, and other environmental
and even aetiological factors, and facilitate the
development and design of management strategies.
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52 Mary CARDOSA, Phoon Ping CHEN
Epidemiology also promotes best clinical practice,
which requires the evaluation of the preventive
strategies and assessment of the outcomes of
different treatment modalities.
Prevalence of chronic pain
e general prevalence of chronic benign pain
worldwide ranges from 2–40% with a median
prevalence of 15% [125]. e extremes of
prevalence rates in this review were obtained in old
studies. A recent European survey indicated that
the prevalence of pain of longer than 6 months’
duration ranges from 12–30% of the general
population [13], with the lowest prevalence rates
in Spain (12%), Ireland (13%) and the United
Kingdom (13%), and highest prevalence in Norway
(30%), Poland (27%) and Italy (26%). Although
Norway has the highest prevalence in this survey,
an earlier report found that the prevalence was
24% [97]. In Australia, the prevalence of chronic
pain was reported to be 17.1% of men and 20% of
women [8], while in Canada it was 29% [83]. In
Hong Kong, the prevalence of pain of longer than
6 months was reported to be 10.8% [85], although
a more recent study found that the prevalence of
pain in the preceding 4 weeks before the interview
was as high as 45.9% [23]. In South East Asia, the
Malaysian’s ird National Health and Morbidity
Survey in 2006 found that the prevalence of
persistent pain lasting for 3 months or more among
adults was 7.1% (Institute for Public Health 2008,
Ministry of Health Malaysia). e prevalence in
Singapore was similar to that of Malaysia, while the
Philippines and India reported rates closer to that of
Australia and Europe (personal communication).
e prevalence of neuropathic pain has been
reported to be 8% in Scotland, compared with
a prevalence of 48% for any chronic pain [107,
116]. Unlike previous studies, neuropathic pain in
this survey was diagnosed using the Self-complete
Leeds Assessment of Neuropathic Symptoms and
Signs score (S-LANSS). e authors reported that
respondents with neuropathic pain had higher
pain intensity, longer duration of pain, poorer
health and greater disability, according to Short
Form (36) Health Survey (SF-36) and Brief Pain
Inventory scores. A similar impact on quality of life
was reported previously [79].
e epidemiology of pain in children has not been
well documented. e prevalence of chronic pain
in children and adolescents has been reported
to be 30.8% (pain >6 months) in a district in
Germany [96] and 25% (pain >3 months) in the
Netherlands [90]. In the German survey (n=749),
the most common pain types were headache
(60.5%), abdominal pain (43.3%), limb pain
(33.6%) and back pain (30.2%) resulting in
sleep problems (53.6%), inability to pursue
hobbies (53.3%), eating problems (51.1%) and
school absence (48.8%). Unlike pain in the other
extreme of age, pain in children has not been
given the attention it warrants. Greater focus on
research and clinical pain management should be
promoted in this group of pain sufferers. More
information on chronic pain in children is covered
in Chapter 19.
Chronic pain affects more than 50% of older
persons living in the community setting, and more
than 80% of nursing home residents [40, 49]. In
another study, 45.8% of older persons admitted
to US teaching hospitals reported pain, with19%
having severe pain and 12.9% dissatisfied with their
analgesia [33]. A study of older Chinese patients
attending outpatient clinics in Hong Kong found
that 61.5% of patients had experienced pain in the
recent 2 weeks, with over half requiring pain relief
medications [80].
In developed countries, the percentage of the
population over 65 years old will rise from 17.5%
to 36.3% by 2050, and the over-80 age group will
more than triple [121]. As the world’s population
is living longer and getting older, epidemiology
of pain in the older persons has become more
important for the planning of future health care
needs of this group.
Chronic pain in older adults is often caused by
more than one clinical diagnosis [53]. Common
conditions causing pain in the older person
include osteoarthritis, postherpetic neuralgia,
spinal canal stenosis, cancer, fibromyalgia, post-
stroke pain and diabetic peripheral neuropathy.
In a previous population survey, age older than
60 years was identified as a risk factor for chronic
pain [85]. Older adults with chronic pain had
more intense pain (median VAS pain score 7.5
compared with 5.0 in younger sufferers) and
were more severely affected by their pain. Older
patients with pain had poorer sleep quality, lower
self-rated health status and a higher proportion of
depression when compared with those in the same
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Epidemiology in Chronic Pain, Gender and Cultural Aspects
age group without pain [80]. More information
on chronic pain in the older person can be found
in Chapter 18.
e prevalence of common pain conditions such as
back pain, headache, orofacial, joint or cancer pain
will be described in the respective sections. e
epidemiology of risk factors, preventive measures
and treatment strategies will also be discussed
elsewhere in the relevant sections.
Gender and Pain
Population-based epidemiological studies have
shown a higher prevalence of chronic pain in women
than men [8, 13]. In addition, many studies have
shown that a number of chronic pain conditions
are more commonly seen in women than men and
these include headaches and migraines [99, 87],
temporomandibular disorders [17], abdominal pain
[57], irritable bowel syndrome [48] and widespread
painful conditions like fibromyalgia [16, 129]. It is
also frequently reported that women have a higher
risk than men for multiple pain conditions [6].
e differences in the experience of pain between
the men and women relate to both sex and gender.
e term “sex” refers to the biological aspects of
identity such as whether the individual has XX or
XY chromosomes, whereas “gender” is more related
to societal influences and expression of masculinity
or femininity [66].
A study on gender differences in pain experiences
to experimentally induced thermal pain among a
Chinese population have found that women were
more sensitive and less stoic in responding to
pain than men [109]. In a subsequent study, the
author found that women had a lower threshold
and tolerance for pressure pain than men [108].
In another study on gender differences in Chinese
subjects with osteoarthritis, Tsai reported that
Chinese women reported greater pain intensity
and interference from osteoarthritis, and had a
greater depressive tendency [117]. is study
found that depression was the mediator of gender
differences and cautioned against the use of gender
differences to explain the experience of pain
among Chinese elders. ese studies indicated
that careful interpretation of gender differences
is required when reviewing epidemiological
studies.
While the evidence suggests that women are more
likely to experience pain conditions than men, the
pattern and differences may be affected by age.
Neck and shoulder pain was reported to be more
prevalent in Norwegian women, and increased
with age [47], while abdominal pain, although
more prevalent in Swedish women compared with
men, decreased with age [1]. Migraine, on the other
hand, has a bell-shaped distribution over the adult
age groups, with the largest difference in female-
male prevalence in the middle years [99]. When
interpreting epidemiological studies, age- and
gender-specific prevalence patterns must be taken
into account as they differ among the different
pain conditions. is is important as they provide
information about the factors that influence the
occurrence of the pain condition and thus facilitate
strategies to prevent and manage these conditions.
While gender differences in pain sensitivity are
partly attributable to social conditioning and
psychosocial factors, many studies have now
indicated that biological mechanisms underlie such
differences. Studies on sex differences in the response
to analgesics have indicated that pain modulation
mechanisms may be different between men and
women. Research on transgenic mice has suggested
that normal males have a higher level of endogenous
analgesic activity, while human studies have found
that mu- as well as kappa-receptors activation and
responses are different between the genders [128].
Well-controlled studies have increasingly shown
that the gender differences in opioid analgesia
depend on many interacting variables including
gonadal hormonal effects, pharmacokinetics and
pharmacodynamics, genetic influences and balance
in analgesic/antianalgesic processes [31, 41]. ere
is evidence that gonadal steroid hormones such as
oestradiol and testosterone modulate sensitivity to
pain and analgesia [27, 42, 66]. Recently, a study in
rats has shown that gender differences in the basal
expression and the modulation of the N-methyl-D-
aspartate receptor activities in dorsal root ganglia
neurons are regulated by sex hormones [78].
Advances in molecular biological technology have
allowed the cloning, mapping and sequencing
of genes, and also the ability to disrupt their
function entirely facilitating genetic research in
pain [81]. Polymorphisms in genes coding in the
neurotransmitter and receptor systems have also been
shown to influence the variability of pain responses in
individuals [35], and some of these genetic variations
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54 Mary CARDOSA, Phoon Ping CHEN
may in fact be associated with the pathogenesis of
conditions such as fibromyalgia syndrome where
there is a higher preponderance in women [16].
In the study by Tsai [117] above, the depression-
mediated gender differences in osteoarthritic pain
and disability may in fact have a genetic basis. More
recently, X- or Y-linked genes have been indicated to
have direct effects in acute nociception, not mediated
by gonadal secretions [43]. Craft and colleagues
indicated that sex differences in pain and analgesia
may be both quantitative and qualitative in nature.
ey envisioned that sex-specific management of
clinical pain may be a reality in the not-so-distant
future [27].
While biological differences leading to increased
sensitivity to painful stimuli have been postulated
as one of the reasons for the observed difference
in prevalence of chronic pain between the sexes,
the relationship between gender and pain is more
complex [65]. Women have been shown to report
more severe clinical pain [118] and experimentally
induced pain than men [94]. When examined
closely within different age groups, women do
not report more pain for every pain condition,
and different pain problems may show differing
patterns. Psychosocial factors such as life-cycle
changes, social and occupational role expectations,
cognitive and emotional experiences of pain, and
different coping approaches and skills play an
important role in determining gender differences in
pain prevalence [58, 65] and contribute to a higher
prevalence in women. ese apparent differences
may also reflect the way men and women respond
to pain, and that there are different social norms for
the expression of pain [32].
In one experimental study, female subjects were
found to have lower tolerances than male subjects
to the pain stimulus [92]. However, interestingly,
reports of pain by male subjects were affected by
the gender of observer. Significantly less pain was
reported in front of a female experimenter than
a male experimenter, whereas in female subjects,
there was no difference [67].
Women are generally more willing to report
pain than men in Western culture [94] and more
likely to seek health care [119]. Women with pain
conditions were reported to use a broader range
of coping strategies than men, and reported more
problem solving and positive statements [120].
ey also sought more social support than men.
ese experiences are more likely associated with
psychological, environmental, social and cultural
influences than biological reasons.
Ethnicity and Cultural
Aspects of Pain
Differences in responses to pain have been observed
in various racial groups within and between
countries. Although the terms “race”, “ethnicity”
and “culture” are often used interchangeably, race
is thought to be biologically determined, while
ethnicity and culture are social constructs [76].
According to the biopsychosocial model of pain,
however, it would seem that ethnicity and culture
would be just as important as contributors to
chronic pain as biological factors (race).
Both laboratory and clinical studies have shown
evidence that people of different ethnicity and
cultures respond differently to pain. Ethnic
differences in experimental pain perception have
been documented from as early as 1944 when
Chapman and Jones reported lower heat pain
thresholds and tolerances among African-American
subjects compared to non-Hispanic Caucasian
subjects [19]. Subsequently, there have been
other studies reporting similar findings, and more
recent publications have added to the information
on ethnic differences, giving an overall picture
of reduced tolerance to experimentally induced
pain stimuli in African-Americans compared to
Caucasians [36, 37, 38, 103].
Pain reporting
In a study of postoperative dental pain, Faucett
showed that Americans of European descent reported
significantly less pain than Americans of African
and Latino descent [39]. Similarly, other studies
comparing African-Americans and Caucasians have
shown that African-Americans reported more pain
than Caucasians after spinal surgery [127] as well
as among those who experienced treadmill-induced
angina [102]. However, there were also studies that
showed no ethnic difference in pain reports in other
acute situations such as in post-trauma pain [115].
In chronic pain conditions, African-Americans
have also been reported to have higher levels of
pain compared to non-Hispanic Caucasians with
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55
Epidemiology in Chronic Pain, Gender and Cultural Aspects
several painful conditions, including acquired
immune deficiency syndrome (AIDS) [12],
arthritis [28] and low back pain [101]. In a study of
chronic pain patients attending a pain clinic, while
pain severity scores were no different, African-
Americans reported higher levels of pain-related
unpleasantness, depression and fear, and scored
higher on scales related to pain behaviour compared
with non-Hispanic white Americans [93]. A recent
study of musculoskeletal pain in Malaysia reported
that the pain rating was higher in women (23.8%)
than in men (17.8%) [124]. Among the multiracial
population, Chinese men reported the lowest age-
standardised pain rating (9.9%), while Indian
women had the highest rating (28.4%).
It is noteworthy that the tools for pain assessment
may present cultural biases when they are used in
individuals of different ethnicity as there may be
an inherent difficulty to conceptualise and quantify
pain. In a study of Aboriginals and Torres Strait
Islanders, it was found that 15.8% of the group was
unable to use the numeric rating scale [98], while
another study reported that 19% of Chinese cancer
patients had difficulty with the same tool [24].
In addition, different ethnic groups and cultures
may use different pain descriptors that may be
interpreted differently outside the group. In one
Chinese study, crucifying pain (10/10) was the most
severe descriptor compared with unbearable (7/10)
or indescribable pain (6/10) [22]. Another study
reported that a vertical visual analogue scoring scale
may be more appropriate for the Chinese patients
as the Chinese language is traditionally written and
read from top to bottom [2].
Pain relief treatment
Studies have shown that ethnicity was a
significant predictor of the dose of postoperative
opioid analgesia prescribed by clinicians [63].
Pharmacogenetic differences between ethnic
groups may lead to polymorphism in metabolising
ability (enzyme CYP2D6) and result in variation
in response to some pain relief medications.
Chinese, for example, have a lower prevalence of
poor metabolisers and a higher sensitivity to some
medications such as codeine [91, 130].
In cases where the analgesia was self-administered
by a patient-controlled analgesia technique, earlier
studies had found that the eventual dose of opioids
consumed was no different between patients of
different ethnicities [84, 118]. However, in a more
recent report of self-rated pain score and patient-
controlled morphine usage in 1,034 women after
elective lower Caesarean section, the authors found
that patients of Indian race in Singapore had the
highest mean pain score and consumed the highest
amounts of morphine [112]; this is similar to
findings in another study on chronic pain [124].
ere is also evidence that male and female
clinicians may respond differently to the
demographic characteristics of patients in need of
pain management [126]. A recent survey of patients
with long bone fractures presenting at an emergency
department found that white patients were more
likely than black to receive analgesics [114]. e
risk of a black patient not receiving analgesic at the
emergency department was 66% greater than for
white patients. Stereotyping ethnic groups in their
responses to pain may lead to under-treatment in
the affected groups.
In another study of patients after cholecystectomy,
it was found that Chinese, Japanese and Filipino
patients received less pain medications than
Caucasians and Hawaiians [110]. e authors
reasoned that the differences may be related to
ethnic differences in analgesic requirement or
cultural bias. Some cultural styles (East Asians are
more stoic) may be more susceptible to under-
treatment than others.
Reasons for ethnic and racial
dierences in pain
A variety of biological, social and psychological
mechanisms may be responsible for observed racial
and ethnic differences in pain reports. Increasingly
more studies have examined whether biological
(genetic) or sociocultural factors could account
for these differences in pain responses, or whether
these factors are influenced by the environment
(the nature-nurture argument).
Biological factors
e mutation of the gene SCN9A that leaves
the individual completely insensitive to pain has
recently been mapped [26, 44]. It is becoming
clearer that other genetic polymorphisms or
gene mutations may also make individuals more
sensitive or susceptible to pain, especially to the
development of chronic persistent pain [82].
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56 Mary CARDOSA, Phoon Ping CHEN
Recent research has found that the risk for
developing intervertebral disc degeneration and its
severity is associated with genetic risk factors and
is highly heritable [56, 133]. Two of these genetic
variants are encoded by the Trp2 and Trp3 alleles in
the COL9A2 and COL9A3 genes. While the Trp3
(but not Trp2) allele has been shown to be more
prevalent in Caucasians (Finnish), it is absent in
the Southern Chinese population [50]. Contrary
to this, in Southern Chinese the Trp2 allele is
a significant risk factor for developing severe
intervertebral disc degeneration, annular tears and
herniations. e contrasting Trp allele frequencies
between the Caucasians and the Chinese indicate
that the genetic risk factors may vary between
different races.
It is also possible that cultural and ethnic factors
can influence activity in higher nervous centres that
modulate pain through the activation of descending
neural inhibitory controls [34]. ere is some
evidence that ethnic differences in pain perception
may be influenced by differences in descending
neural inhibitory controls [18]. is mechanism
may account for the observation in Hindu devotees
who are able to tolerate the piercing of their body
with sharp objects during the aipusam rituals
which occur every year in countries like Malaysia.
Similarly, cultural norms could account for the fact
that in China, even young children are able to accept
having acupuncture done to them as a treatment
for any ailment, in contrast to the experience in
Western medicine settings where injections are
avoided as far as possible when treating paediatric
patients because of children’s fear of needles.
Cultural practices such as meditation may also
modulate pain responses. Kakigi showed that there
was a marked reduction in functional magnetic
resonance imaging activity in the thalamus, insula
and cingulated cortex with the same painful stimulus
during meditation [55]. In a non-meditative state,
the subject reported pain scores of 8/10 compared
to 0/10 in response to the same stimulus when he
was in deep meditation.
Psychosocial factors
Psychological factors including different pain
coping styles of different ethnic groups may lead
to differences in the report of pain and subsequent
disability [34]. African-Americans with rheumatoid
arthritis reported significantly greater use of
distraction and passive coping mechanisms like
praying and hoping, while Caucasians reported
more use of ignoring pain and a greater perceived
ability to control pain [54].
Ethnic minorities are also more likely to
experience high levels of chronic stress due to
social discrimination and racism [34]. is stress
produces chronically high levels of sympathetic
activation and physiological exhaustion [25], and
leads to limited coping resources, which in turn
makes it more difficult to deal with persistent pain
[34].
Social factors including socioeconomic status and
ethnic background can affect access to health care.
Under-treatment of pain in minority populations
has been previously reported [105, 110]. As
unrelieved acute pain increases the risk of developing
chronic pain states [59, 89], patients from socially
disadvantaged groups may be more at risk of being
exposed to unrelieved pain [34]. Furthermore, lack
of trust of patients from ethnic minority groups in
their physicians [46] may lead to delay in seeking
health care, which in turn increases risk of having
unrelieved pain.
Ethnic factors may influence the appraisal of pain
and the subsequent responses. e meaning of
pain may be influenced by sociocultural factors, for
example, pain as retribution or pain as something
to be mastered [4]. is can have a major influence
on both emotional and behavioural responses,
including the decision whether to seek treatment
and from whom to seek treatment. ere is now
evidence that cultural factors such as health
beliefs and expectation may affect common
musculoskeletal symptoms and associated
disability [72]. In Malaysia, a study looking at
pain complaints in primary care settings showed
that a higher proportion of Indian patients visited
government clinics, while more Chinese patients
sought out private doctors for complaints of
pain [132]. is difference in health care-seeking
behaviour of different races may lead to differences
in quality of pain relief experienced by the different
ethnic groups.
Cultural factors may also strongly influence the
expression of pain. In some cultures such as the
Chinese, expressing pain openly may be seen as
a weakness and therefore patients often remain
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Epidemiology in Chronic Pain, Gender and Cultural Aspects
stoic despite pain and suffering. Conversely, in
other cultures such as Indians, pain and grief are
expected to be expressed openly. In Malaysia, this
may have led to stereotyping Indians as having a
lower tolerance to pain. While this may well be
true, there are no specific studies looking at the
pain threshold and tolerance levels in different
Asian racial groups to substantiate this belief.
Indeed, the differences in pain experience among
the ethnic groups, at least in part, may be explained
by the differences in descending neural inhibition
[18]. A study by Chung et al. [24] on cancer pain
in Hong Kong Chinese showed that although the
prevalence of pain was the same as that reported in
Western populations, the severity of the pain tended
to cluster around the lower levels (“mild pain”)
compared with the Western reports. In another
study, the authors found that both geographical
location and cultural groups resulted in a different
emphasis on the different aspects of quality of life
[100].
Assimilation and acculturation into a foreign society
may affect how individuals respond to pain. ose
who have successfully integrated into the foreign
society may be less affected by their own customs,
rituals and values [76]. ey tend to behave and
respond in accordance with the expectations and
values of their adopted society. Research with adult
twins supported the views that cultural patterns
of behaviour within families, and not genes,
determined perceived sensibility to pain [73]. In a
study of Chinese and non-Chinese Canadian infants
receiving routine immunisation, it was found
that significant differences in acute pain response
occurred at 2 months of age with the Chinese
infants showing greater response [95]. e authors
concluded that cultural influences occurred well
before acquisition of language. A recent UK study,
however, found that acculturation only explained
part but not all the differences between South
Asian ethnic groups (1,165 Indian, 401 Pakistani
and 348 Bangladeshi) and white Europeans in the
prevalence of widespread pain [88].
Summary
e clinical relevance of ethnic influences on pain
requires further study as it is still unclear how
consistent are the differences in clinical presentations
across ethnic groups. More importantly, is ethnicity
associated with differential pain treatment due to
the attitudes of health care professionals?
Experience with chronic pain patients in Malaysia
and Hong Kong showed that although they have
vastly different cultural backgrounds and beliefs
compared with patients from Western cultures, there
is a lot of similarity in the responses of the respective
patients to chronic pain, and the resulting distress
and disability. Similarly, cognitive behavioural
therapy-based pain management programmes that
teach self-management strategies for chronic pain,
although developed in the West, have been applied
successfully in Malaysian and Hong Kong patients
of different ethnic groups [86]. ese programmes
are conducted using local languages, applying
cognitive behavioural therapy principles but using
culturally appropriate examples and illustrations so
that they are meaningful to the patients.
Factors affecting the report of pain, the responses
to chronic pain and its effect on work, activity and
mood are multiple and influence the prevalence of
chronic pain in different populations. Although
gender, ethnic and cultural differences may have
an impact on patients’ response, it is important
to be aware that stereotypes and prejudices based
on gender and ethnicity alone may influence the
diagnosis and treatment offered to patients of
different background.
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