Master Thesis
HALMSTAD
UNIVERSITY
Master's Programme in Health and Lifestyle, 120 credits
The impact of chronic widespread pain on health status and long-term health
predictors: a general population cohort study
Health and Lifestyle, 30 credits
Halmstad 2019-05-27 Charlotte Sylwander
The impact of chronic widespread pain on health status and long- term health predictors: a general population cohort study
Thesis frame
Writer: Charlotte Sylwander
Subject Health and lifestyle
Credits 30 hp
Cityand date Halmstad 2019-05-27 Opponentship and respondent date: May 22, 2019
Titel Kronisk utbredd smärtas påverkan på hälsostatus och långsiktiga hälsoprediktorer: en allmän populationskohort
Författare Charlotte Sylwander
Akademi Akademin för Hälsa och Välfärd
Handledare Stefan Bergman och Ingrid Larsson
Examinator Eva-Carin Lindgren
Tid HT 2018 - VT 2019
Sidantal 8
Nyckelord Kroniskt utbredd smärta, könsskillnader, hälsostatus, hälsoprediktorer
Sammanfattning
Bakgrund
Tidigare forskning visar att långvarig generell smärta (CWP) har en negativ påverkan på hälsostatus och dagliga aktiviteter. Riskfaktorer för att utveckla CWP är t.ex.
kvinnligt kön, andra kroniska sjukdomar, rökning, inaktivitet, sömnproblem och övervikt. Den genomsnittliga prevalensen av CWP i den allmänna befolkningen är 9,6–
15 %. Resultat på könsskillnader varierar gällande prevalens, upplevelse av smärta, påverkan på det dagliga livet, arbetslivet samt hälsostatus. Det övergripande syftet var därför att undersöka CWP:s påverkan på hälsostatus samt långsiktiga livsstilsfaktorer för en bättre hälsa för dem med CWP.
Metod
Studien är en befolkningskohort med 975 deltagare (442 män, 533 kvinnor) i åldern 35–54 år med en 12- och 21-års uppföljning. CWP definierades enligt American College of Rheumatology (ACR) definition som säger att smärta ska vara närvarande i minst tre månader, under och över midjan, på båda sidorna av kroppen samt axialskelettet för att klassificeras som generell. Med hjälp av en ritad smärtfigur och ytterligare frågor sorterades deltagarna in i tre olika smärtgrupper: ingen långvarig smärta (NCP), långvarig regional smärta (CRP) och CWP. Frågeformuläret bestod av frågor om livsstilsfaktorer (personligt stöd, vänskapskrets, rökning, alkoholintag, fysisk aktivitet samt sovvanor) och SF-36 som mäter hälsostatus. Skillnader i hälsostatus analyserades genom ett oberoende t-test och hälsoprediktorer genom logistisk
regressionsanalys. Resultatet analyserades ytterligare utifrån Tenglands två- dimensionella hälsoteori och den relativa genusteorin.
Resultat
Prevalensen av CWP var högre bland kvinnor vid samtliga tidpunkter och hälsostatus var statistiskt signifikant lägre för både kvinnor och män med CWP (p < 0.001). Det fanns inga könsskillnader av klinisk relevans. Vid 12 års uppföljningen hade 58 % av kvinnorna och 53 % av männen långvarig CWP (p < 0.001). Vid 21 års uppföljningen hade 59 % av kvinnorna och 29 % av männen långvarig CWP (p < 0.001).
Hälsoprediktorer för bättre hälsostatus för CWP-drabbade var manligt kön (OR 3,03–
6,76), socialt stöd (OR 9,27), inga sömnproblem (3,48–4,76), före detta rökare (4,38–
7,83) och att varje vecka dricka alkohol (OR 4,94).
Slutsats
Fler kvinnor än män rapporterade långvarig CWP i ett 12- och 21-års perspektiv, men bland de som hade CWP var hälsostatusen lika dålig hos kvinnor och män. Att inte ha några sömnproblem var starkt förknippat med en bättre mental hälsa och personligt stöd kan vara av betydelse för en bättre vitalitet. Den högre prevalensen bland kvinnor samt manligt kön som hälsoprediktor verkar vara påverkade av de psykosociala mekanismerna för genus. Hälsostatus visade emellertid inte någon koppling till den relativa genusteorin. Resultet innebär att även om män har en lägre prevalens av CWP bör tillståndet betraktas detsamma för män som hos kvinnor i vården. Vidare forskning bör studera långvarig CWP och möjliga confounders för att faststlå köns- och genusskillnader i ett långsiktigt perspektiv.
Title The impact of chronic widespread pain on health status and long-term health predictors: a general population cohort study
Author Charlotte Sylwander
Department Academy of Health and Welfare
Supervisor Stefan Bergman och Ingrid Larsson
Examiner Eva-Carin Lindgren
Period HT 2018 - VT 2019
Pages 8
Keywords Chronic widespread pain, sex differences, health status, health predictors
Extended abstract
Background
Previous research states that chronic widespread pain (CWP) has a negative impact on health status and daily life activities. Risk factors for developing CWP are, e.g. female sex, other chronic diseases, smoking, inactivity, sleeping problems and obesity. The average prevalence of CWP is 9.6-15% in the general population. The results vary regarding sex differences in prevalence, pain experience, impact on daily life, work, and health status. Therefore, the overall aim was to investigate CWP’s impact on health status and long-term lifestyle predictors for better health when having CWP.
Method
The study is a general population cohort study including 975 participants (442 men, 533 women) at the age of 35-54 years with a 12- and 21-year follow-up. CWP was defined according to the American College of Rheumatology’s (ACR) definition stating pain must be present for at least three months, below and above the waist, on both sides of the body, and the axial skeleton to be classified as widespread. Using a pain mannequin and additional questions the individuals were sorted in three different pain groups: no chronic pain (NCP), chronic regional pain (CRP), and CWP. The questionnaire included questions about lifestyles factors (personal support, friendship circuit, smoking, alcohol intake, physical activity and sleeping habits) and SF-36 measuring health status. Differences in health status were analysed by independent samples t-test and health predictors by logistic regression analysis. The results were further analysed using Tengland’s two-dimensional health theory and the relational gender theory.
Results
The prevalence of CWP was higher among women during all time points, but health status was statistically significant reduced for both women and men with CWP (p
<0.001) showing no sex differences of clinical relevance. At the 12-year follow-up, 58% of the women and 53% of the men had persistent CWP (p <0.001). At the 21-year follow-up, 59% of the women and 29% of the men had persistent CWP (p <0.001).
Health predictors for better health when having persistent CWP were male sex (OR 3.03-6.76), having social support (OR 9.27), no sleeping problems (OR 3.48-4.76), being a former smoker (OR 4.38-7.83) and a weekly intake of alcohol (OR 4.94).
Conclusion
More women reported persistent CWP in a 12- and 21-year perspective than men, but when having CWP the health status was equally as bad among women and men.
Modifiable health factors such as having no sleeping problems was strongly associated with better mental health, and personal support could be of importance for a better vitality. The higher prevalence reported among women and male sex as a health predictor seems to be influenced by the psychosocial mechanisms of gender. However, health status did not show any association with the relational gender theory. The results suggests, even though men have less prevalence of CWP the condition should be regarded as having the same impact for women and men in health care. Further research should continue studying persistent CWP and possible confounders to establish the sex and gender differences in the long-term perspective.
Table of contents
1. Introduction ... 1
2. Theoretical framework ... 1
3. Method ... 3
3.1 Design ... 3
3.2 Questionnaire ... 3
3.3 Analyses... 4
3.4 Ethical considerations ... 4
4. Discussion ... 5
4.1 Results ... 5
4.2 Methodological considerations ... 7
4.2.1 Internal validity ... 7
4.2.2 External validity ... 8
4.3 Implications ... 8
5. References ... I 6. Appendix – Manuscript ... IV
1. Introduction
Chronic widespread pain (CWP) is a servere condition affecting approximately 9.6-15%
of the general population (Andrews, Steultjens & Riskowski, 2018; Mansfield, Sim, Jordan & Jordan, 2016). The condition is associated to a reduced health status and has a negative impact on work, and daily life activites (Dureja et al., 2013; Gerdle, Björk, Cöster, Henriksson, Henriksson & Bengtsson, 2008; Järemo, Arman, Gerdle, Larsson &
Gottberg, 2017). There are reported sex differences in prevalence and impacts on health status but why these excist are still not fully understood (Fillingim, King, Ribeiro- Dasilva, Rahim-Williams & Riley, 2009; Racine, Tousignant-Laflamme, Kloda, Dion, Dupuis & Choinière, 2012). Therefore, the overall aim was to investigate CWP’s impact on health status and long-term lifestyle predictors for better health when having CWP.
2. Theoretical framework
How health is defined facilitates the goals and strategy to achieve, maintain or improve health (Tengland, 2007). If health merely is the absence of disease, the strategy to achieve health is to cure the disease. However, if health is seen as something more or something else the strategy will be different. The definition of health according to WHO is “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (World Health Organization, 1948). Conversely, the main population of the present study has CWP and is therefore left out in this definition since the subjects do not have a “complete physical, mental or social well-being” (Fillingim et al., 2009).
Therefore, the definition of health promotion in the Ottawa documents was used instead.
The definition states “the process of enabling people to increase control over and to improve their health” (World Health Organization, 1986). The health promotion definition allows for improved health stating one can have more or less health since it is improvable. It is allowing an individual with CWP having some amount of health. In covariance, Tengland’s (2007) two-dimensional theory of health has an central role in the view of health. It is a pluralistic theory of health and states that health is both seen as ability and well-being. More precise, 1) “to have developed the abilities and dispositions that members of one’s culture typically develop, and be able to use them in acceptable circumstances” and, 2) “health is to experience positive moods and sensations, the kinds that have internal causes”. The two dimensions are ability – disability and well-being – suffering, meaning a person can be anywhere in those two dimensions. Together they make up the health dimension good health – ill health (Tengland, 2007).
The two-dimensional health theory has its origin in the monistic health theories where health is explained as ability or well-being (Tengland, 2007). The holistic theories (health as ability), have flaws according to Tengland. He argues, having an ability is not a guarantee for health and the same goes the other way around, lacking an ability is not equal to reduced health. Abilities such as driving a car do not constitute health but are competencies requiring health if they are to be developed. It is the absence of skills than reduced health (Tengland, 2016), and for reduced health, one can either lose an ability temporarily or permanently (Tengland, 2007). Tengland (2010) continues by adding the
environment explaining the environmental circumstances can prevent specific abilities.
For example, bad weather can mean running is avoided. However, it is not ill health if the environment is the prevention factor from reaching particular goals. To truly capture all aspects of health it is necessary to include another view despite losing some homogenous in the theory (Tengland, 2007). Having abilities are, however, not enough to be healthy but one has to be able to utilize them as well (Tengland, 2010). The second view is health as well-being, where “well-being” is referred to as “a subjective experience of some kind of feeling” with the antonyms “suffering” (Tengland, 2007). To separate health-related well-being from well-being not affecting the health, there is a distinction of the immediate cause within the person (health-related) and external causes (not health-related). The health-related well-being takes form in sensations or moods with direct internal cause and not emotions which have an external cause. The two perspectives with some modification results in the two-dimensional health theory. If there is a decrease in any of the two dimensions (ability-disability and well-being-suffering), there is a decrease in health, and if there is an increase, there is an increase in health (Tengland, 2007).
Having CWP will likely decrease both ability and well-being; however, it is not necessarily equal to ill-health. According to Tengland (2007), health will be reduced if losing an ability temporally or permanently which is one consequence of CWP. Having CWP decreases the ability to do both work and daily life activities such as driving a car, exercise and doing household chores (Dureja et al., 2013; Harker et al., 2012). However, lifestyle factors can also have a positive impact on people’s health when having chronic pain (Skillgate, Pico-Espinosa, Hallqvist, Bohman, & Holm, 2017). Giddens (1991) explains lifestyle as embraced routinized practices in relation to the self-identity. The routines of a lifestyle have small every-day decisions such as what to eat or what to wear.
These decisions are in relations to the self-identity, and each of these small decisions is decisions not only for how to act but for who to be. Lifestyles are not always chosen and could more or less be forced. For example, work and socio-economics can limit the options because, for example, all employments are not available for everyone. However, in the context of what is offered in life, the person can choose for herself. For example, an individual could neglect a proven healthy lifestyle if it contradicts with the preferred lifestyle. Lifestyles are more or less substantially, and with a change of life, the lifestyles choices also change (Giddens, 1991).
Additionally, since a part of the aim were to investigate sex differences the relational gender theory (Sánchez-López & Limiñana-Gras, 2017) was found suited as a part of the theoretical framework. There is a difference between sex and gender. ‘Sex’ refers to
“biological construct premised upon biological characteristics enabling sexual reproduction”, and ‘gender’ refers to “a social construct regarding culture-bound conventions, roles, and behaviours for, as well as relationships between and among, women and men and boys and girls.” (Krieger, 2001). To understand the gender processes that affect health the categorical dichotomize thinking (‘sex’) cannot be relayed on (Connell, 2012). The relational gender theory explores the social structures and practices of men and women (Sánchez-López & Limiñana-Gras, 2017). A gender perspective in
public health is essential in several aspects. Asides from leading to increased public health by noticing life conditions with gender differences, a gender perspective can raise questions regarding the debated health paradox (women having more extended life expectancy than men but worse health) (Hammarström & Hensing, 2008). The relational gender theory consider the change of gender structures and is said to be a promising framework to better understand the association between health and gender (Sánchez- López & Limiñana-Gras, 2017).
When Tengland (2016) discusses the environmental aspects of health, a gender perspective is mentioned in the form of patriarchal norms. Stating, these norms can hinder people from achieving specific goals. However, a reduction in health can only be concluded when an individual cannot achieve vital goals despite an acceptable environment. More précised, if the environment is not favourable and the cause of the prevention, it is not equal to ill health (Tengland, 2010).
3. Method
3.1 Design
The epistemology of the researcher is of most importance to understand how the researcher has interpreted the results. Exploring the affection of this is a vital part of the post-positivism approach, which is the view in the present study (Ryan, 2006). In positivism, researchers believe that complete knowledge can be obtained by observations and experiments rational interpreted. The correct and exact answer comes from quantification and validated measurements, and the research and data represent reality.
Post-positivism, however, opens for the idea of multiple ontologies instead of dualistic.
Knowledge can be both instead of either, and the researcher is striving for a more distanced view seeing the whole picture. Resulting in more liberal research including for example theories. It also recognizes ethical considerations to a greater extent such as the purpose and use of the study (Ryan, 2006).
3.2 Questionnaire
The questionnaire used in this study consisted of 52 questions including socio- demographic variables, pain questions with a pain mannequin, questions regarding lifestyle factors, and additional the Short-Form General Health Survey (SF-36 (Bergman et al., 2001). The 52 questions were chosen by a panel of six physicians mainly from prior studies (Bergman, 2001). To assure that musculoskeletal pain was measured the drawn pain mannequin did not include the head or the abdomen. In the present study, nine of the questions was used and analysed. These being the pain mannequin, if experienced pain more than three months, sleeping problems, physical activity, smoking habits, alcohol intake, personal support, friendship circuit and education level.
The questions were identical every year except for the questions about alcohol intake and physical activity. These were updated in 2007, and the question about physical activity was updated in 2016 once again. The updates were due to new standards from the Swedish
National Board of Health and Welfare (Haskell et al., 2007). The question about alcohol intake was considered similar enough and was re-coded into four answers: “Never- rarely”, “Every month”, “Every week” and “> 4 times a week”. The two times updated question on physical activity had more changes. In 1995 and 2003 the question asked only had three possible answers, “No”, “Yes, 1-2 times a week” and, “Yes, more than two times a week” on the question “Do you exercise regularly?”. In 2007, the question was updated with four possible answers, these being of explaining sort including examples of activities such as “talking walks”, “watching TV”, “gardening”, “swimming”
etc. These answers were created to be comparable to the former. Between 2007 and 2016 the Swedish National Board of Health and Welfare created national guidelines and standardised questions regarding lifestyles including physical activity, according to updated recommendations from the American College of Sports Medicine and the American Heart Association (Haskell et al., 2007). These questions were adopted, and the one about exercise was used in the analysis. The question asks for minutes of exercise per week and has six different answers ranging from 0 minutes to more than 120 minutes of exercise per week. Resulting in a final re-coded variable with three answers stating:
“Not physical active” including answers of no (1995 questionnaire), no activities resulting in sweating (2007) and, limited amount of exercise (< 30 minutes) (2016):
“Moderately active” including exercise 1-2 times a week (1995 and 2007) and 30-90 minutes a week (2016): and third, “Active” including exercise more than 2 times a week (1995 and 2007) and 90- >120 minutes (2016).
SF-36 with the Swedish translation has been tested for reliability and construct validity (Marianne Sullivan, Karlsson, & Ware Jr, 1995). SF-36 consist of 36 questions and 35 of these were converted into eight different sub-categories according to the recommended method (M Sullivan, Karlsson, & Ware, 1994). The sub-categories are Physical Functioning (PF), Role function – Physical aspect (RP), Bodily Pain (BP), General Health perception (GH), Vitality (VT), Social Functioning (SF), Role function – Emotion aspect (RE) and Mental Health (MH). The sub-categories can be divided into a physical or mental dimension. PF, RP, BP and GH relates to the physical dimension and VT, SF, RE and MH to the mental dimension (Järemo et al., 2017)
3.3 Analyses
To answer the overall aim, health status from SF-36 was analysed by using independent samples t-test and health predictors by logistic regressions analyses. These results were further analysed using Tengland’s two-dimensional health theory (Tengland, 2007) and the relational gender theory (Sánchez-López & Limiñana-Gras, 2017).
3.4 Ethical considerations
In accordance with the Declaration of Helsinki (World Medical Association, 2013), all participants received information regarding the aim of the study, the method and the voluntary rights to at any moment without further explanation drop out of the study.
Precaution to protect the participants confidentially was taken by decoding identity into
serial numbers and having the key code in safekeeping only available for the responsible researcher of the larger research project, the EPIPAIN study (World Medical Association, 2013). There were no further risks for the participants considered. Moreover, the study intended to follow the four general ethical principles: autonomy, beneficence, non- maleficence, and justice (Garrett, Baillie, & Garrett, 2001). Respect for autonomy was confirmed by respecting the privacy and integrity of others, protecting and handling the confidential information with care, and containing consent for the study. Beneficence refers to preventing harm and danger, and to provide benefits with the study by making sure the benefits are superior to the risks. Non-maleficence is similar to the beneficence principle and refers to “do not” instead of “prevent”. Meaning, e.g. “do not cause needless pain”. Lastly, justice refers to treating each participant equal according to need, effort, contribution and merit (Garrett et al., 2001).
4. Discussion
4.1 Results
The aim of the study was to investigate CWPs impact on health status in women and men in the age of 35-55 years in a sample from the general population. The aim was further to investigate lifestyle predictors for better health in those with CWP in a 12- and 21-year perspective. The main findings in the study suggest that women and men with CWP have the same decreased health, but women have longer persistent CWP. Health predictors for those with CWP were male sex, social support, former smoker, weekly intake of alcohol and no sleeping problems.
Women reported CWP more frequently than men as well as persistent CWP. When gender roles are being examined studies have shown that women are more willing to report pain (Defrin et al., 2009; Fillingim et al., 2009) and Rovner et al., (2017) found that women had a higher pain acceptance than men. Furthermore, Caroli and Weber- Baghdiguian (2016) found that in a female-dominated work environment there is a higher acceptance for reporting health issues for both women and men than in a male-dominated or mixed environment. Civardi et al., (2018) examined prevalence before and after an education program where definitions and the pathophysiology of chronic pain were discussed, and found that the sex-difference seen before was no longer statistically significant after the program. This could indicate that the psychosocial mechanisms of gender greatly influence a higher prevalence among women. Moreover, stress is a risk factor for chronic pain (Dean & Söderlund, 2015) and stress in daily life and work-related stress were associated with the believed cause behind CWP (Järemo et al., 2017). Since women experience more stress than men (Folkhälsomyndigheten, 2017), this could be one explanation of why women report more persistent CWP.
According to Tengland’s (2007) two-dimensional health theory, health status is decreased when either ability or health-related well-being is reduced. The results showed a statistically significant reduction in all eight sub-categories in SF-36 when comparing to the group with NCP and CRP. A decrease in physical sub-categories such as PF and RP will likely hinder the individual from performing some abilities. It could either be a
temporary loss, for example, the individual cannot run in some periods or a permanent loss stating that the individual can never run due to the physical reduction (Tengland, 2007). Following the two-dimensional health theory, this would mean a reduced health status which is shown in the results of decreased GH. The same pattern can be seen regarding the psychological aspects of health status. VT, SF and RE can all have an impact on health-related well-being (sensations or moods) (Tengland, 2007). Having lower VT can be connected to an experience of a lower SF and RE and vice versa. All these were low including MH stating that having a reduction in well-being is associated with reduced health as Tengland (2007) suggests. This study seems to be one of the first studying sex-difference in health status when having CWP. Since there were no differences of clinical relevance this could indicate that the current results are in favour of the two-dimensional theory stating that a non-acceptable environment (gender structures) does not affect health status (Tengland, 2016).
The health predictors found in the present study were male sex, social support, former smoker, weekly intake of alcohol and no sleeping problems. As discussed above male sex as a health predictor could be partly explained by the lower pain acceptance and willingness to talk about pain or health issues among men (Caroli & Weber-Baghdiguian, 2016; Defrin et al., 2009; Rovner et al., 2017). Moreover, having a stereotypical macho attitude was associated with lower pain sensitivity (Defrin et al., 2009; Fillingim et al., 2009), and both men and women agreed that men should tolerate more pain than women (Fillingim et al., 2009). Thus suggesting, that gender does interfere with the results causing a failure in accounting for the evidence behind the biological influence of the male sex (Sánchez-López & Limiñana-Gras, 2017). The health predictors related to the mental dimension of health were; having personal support and no sleeping problems.
Both affected VT positively and having no sleeping problems was also connected to better MH. According to the two-dimensional theory, increased health-related well-being would equal an improved health status (Tengland, 2007). Meaning, having personal support and no sleeping problems affects the well-being dimension expressed in positive sensations or moods, and thereby health increases. In the physical dimension, a former smoker and weekly intake of alcohol were found being health predictors for PF. Quitting smoking improves the musculoskeletal health and functional capacity (Dean & Söderlund, 2015) which increase ability and with that the health status (Tengland, 2016). Besides an effect of alcohol itself, possible explanations could be that people with worse health refrain from alcohol or that people with good health consume alcohol in positive circumstances.
Giddens (1991) explains that a lifestyle could be forced and when having CWP there is a forced change when former abilities no longer can be executed. This affects the self- identity and possibly the well-being since a lifestyle is embraced and strongly connected to the identity (Giddens, 1991; Tengland, 2007). When life changes the choices of lifestyle also change (Giddens, 1991). In accordance with the findings of the study, individuals with CWP could preferably choose an active lifestyle to prevent sleeping problems (Skarpsno, Nilsen, Sand, Hagen, & Mork, 2018), quit smoking, trying to surround themselves and talk to peers, friends or health care personnel for support.
4.2 Methodological considerations 4.2.1 Internal validity
There are both strengths and limitations in the study affecting the internal validity (Laake, Benestad, & Olsen, 2007). The questionnaire was tested on 50 individuals in a pilot study and resulted in both good content and face validity (Bergman, 2001). To assure criterion validity, a question including eight different statements about pain were included and tested for. The reliability was tested by having 28 individuals filling out the questionnaire an additional time ten days after the first one resulting in good test-retest reliability (Bergman, 2001). The updated questions (alcohol intake and physical activity) have not been validated against the previous question. The question about physical activity has changed noticeably and could, therefore, bias the results. However, the question about alcohol intake was considered very similar to the previous question, and the risk for bias was deemed to be small. Overall, the questionnaire is both validated, and reliable strengthening the internal validity (Laake et al., 2007)
At baseline, there were differences found in characteristics between women and men;
however, these differences were no longer seen in the CWP group indicating that this group is a homogeneous group. Having a homogenous group decreases the risks for confounders affecting the main variables (Silman & Macfarlane, 2002). However, there is a risk of non-response bias in prospective cohort studies (Laake et al., 2007). The drop- out rate was 25% in the 12-year follow-up, 22% in the 21-year follow-up, and these groups differed from the participants. However, the only difference found in both drop- out groups (12- and 21-year follow-up) was that more individuals with NCP dropped-out than with CRP and CWP. Since this study focused on the CWP group the risk for non- response bias is, therefore, considered small (Laake et al., 2007). However, having a drop- out rate of more than 20% threatens the internal validity (Dettori, 2011) and is, therefore, a limitation of the study. To minimize the risk of a non-response bias (Silman &
Macfarlane, 2002), the questionnaire was sent out by post with two reminders for each occasion. In 2016 during the 21-year follow-up, the questionnaire was also available on the web.
In the current study, other diseases have not been examined. Mundal, Gråwe, Bjørngaard, Linaker, and Fors (2014) found that the strongest predictor for the persistence of CWP were other chronic diseases which could have had an impact on the results in the present study. Moreover, anaesthetics and other medicines have neither been examined, which also could be a confounder. Third, during the 21 years studied, the individuals move between the different pain groups. In the logistic regression analysis, all with CWP at baseline were included no matter if they resolved from CWP and the analyses were not controlled for pain group. This could have affected the health predictors not giving the true association to better health (Laake et al., 2007), e.g. increasing the odds ratio for male sex since men recovered to a greater extent than women. Men have also shown having a lower risk for persistent CWP (Mundal et al., 2014). Since age and male sex are associated with CWP (Bartley & Fillingim, 2013; Mansfield et al., 2016), these were controlled for
in the logistical regression analysis to prevent bias. Regarding the sex differences in both prevalence and persistence of CWP, and the analysis from the rational gender theory, an essential factor to consider is whether women over-report and men under-report (gender- related biases) or if the differences are a gender-based difference in endogenous pain modulation (Fillingim et al., 2009).
4.2.2 External validity
The participants were randomly selected from the computerised Swedish nation population register, and every 18th person was selected to the EPIPAIN study (Bergman et al., 2001). From those included, every man and women at the age of 35-54 were selected to the present study. This reduces the risk of selections bias and increases the possibility that those selected represent a fair selection of the studied population. In turn, this increases the external validity – the generalizability (Laake et al., 2007). However, the health predictors were not controlled for pain group which could affect the external validity negatively since there is no certain exposure of pain level at the different time- points indicating that the results may not be generalisable to all with CWP (Szklo, 1998).
Moreover, health status for those with CWP did not change over 21 years which, in turn, increases the external validity because of the stability of the results (Szklo, 1998).
4.3 Implications
The present study found no differences in health status between men and women which are results of value for the society. First, the findings suggest there has been no change in CWPs impact on health status during measured years 1995 to 2016. This indicates a need for an evaluation regarding current treatments. Second, men with CWP should be treated and met to the same degree as women with CWP. There are differences in treatment depending on sex and gender, and consider the findings; further research should focus on if the different treatments are ideal or not. The results also stated that the persistence of CWP differ more after a 7-12-year time where men recovers to a greater extent than women. Further research should continue studying persistent CWP and possible confounders to establish these differences in the long-term perspective. Moreover, research should continue exploring the effect gender roles and structures have on prevalence, experience and view of CWP.
5. References
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Arvidsson, S., Arvidsson, B., Fridlund, B., & Bergman, S. (2008). Health predicting factors in a general population over an eight-year period in subjects with and without chronic
musculoskeletal pain. Health and Quality of Life Outcomes, 6(1), 98. doi:10.1186/1477-7525- 6-98
Bartley, E. J., & Fillingim, R. B. (2013). Sex differences in pain: a brief review of clinical and
experimental findings. British journal of anaesthesia, 111(1), 52-58. doi:10.1093/bja/aet127 ] Bergman, S. (2001). Chronic musculoskeletal pain: a multifactorial process: FoU-Centre; Spenshult;
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6. Appendix – Manuscript
The impact of chronic widespread pain on health status and longterm health predictors: a general population cohort study
Abstract
Background: Previous research states that chronic widespread pain (CWP) has a negative impact on health status; however, results vary regarding sex differences and reported health status. This study investigates the sex differences in health status in a 21-year follow-up and if lifestyle factors can explain better health when having CWP.
Method: A general population cohort study including 975 participants at the age of 35-54 years with a 12- and 21-year follow-up. CWP was measured via a pain mannequin, and the questionnaire included questions about lifestyles factors and SF-36 measuring health status. Differences in health status were analysed by independent samples t-test and health predictors by logistic regression analysis.
Results: The prevalence of CWP was higher among women during all time-points, but health status was statistically significant reduced for both women and men with CWP (p <0.001) showing no sex differences of clinical relevance. At the 12-year follow-up, 58% of the women and 53% of the men had persistent CWP (p <0.001). At the 21-year follow-up, 59% of the women and 29% of the men had persistent CWP (p <0.001). Health predictors for better health when having persistent CWP were male sex (3.03-6.76), having social support (OR 9.27), no sleeping problems (OR 3.48-4.76), being a former smoker (OR 4.38-7.83) and a weekly intake of alcohol (OR 4.94).
Conclusion: Women and men with CWP have the same worsen health status, but men recover from CWP to a greater extent in a long-term perspective. Having male sex, social support, being a former smoker, and no sleep problems were associated with better health status in those with persistent CWP.
Keywords: Chronic widespread pain, Sex differences, Health status, Health predictors
Introduction
Chronic pain is a common health problem [1] and refers to pain that persists or recurs for longer than three months [2]. The prevalence of chronic pain in the general population range from 13% to 46%
[3-8], being higher among women [4, 5, 7-10], and increasing with age [3-6, 8-10]. The condition chronic widespread pain (CWP), is usually defined according to ACR cirteria as pain lasting for a minimum of 3 months, present on both sides of the body, below and above the waist, and the axial skeleton [11]. The average estimated prevalence of CWP range from 9.6-15% [4, 12, 13] and there are several risk factors for developing CWP, e.g., older age, female sex, smoking, excessive body mass, inactivity, depression, sleep disorders, and stress [4, 13-16].
Chronic pain is associated with poorer general health [10, 16-18] and people with chronic pain show a higher level of depression, anxiety, helplessness and dissatisfaction [17, 19]. Chronic pain has a negative impact on daily life and work activity [6, 8, 9, 19]. It affects the ability to do household chores, walk, exercise, drive a car, concentrate, sleep, but also affect sexual relations, the possibility to attend social activities or maintaining an independent lifestyle [6, 8, 19].
Factors associated with a better health status when having CWP are, for example, male sex, younger age, higher socioeconomic status, having emotional support, and suitable sleep structures [10].
Research on pain, gender and sex have increased dramatically since 1995 [1], but still, little is known about the cause behind the sex differences in prevalence and experience of pain [1, 20, 21].
Many attempts have been made to establish answers but with contradicting results. Biological factors such as hormones and neurochemistry [1, 22], psychosocial [22, 23] and methodological biases [21] are all part of the current explanations.
Mogil [24] argues for three explanations: 1) women are more willing to report pain and to seek out health care, 2) women develop painful conditions in a higher extent due to a greater sensitivity to common chronic pain syndromes, 3) women might have a higher sensitivity to pain or a lower pain tolerance than men. However, the results are too inconsistent to be able to determine which of the three scenarios being the most convincing explanation [24]. The prevalence of chronic pain is higher among women; however, a
study showed that after an educational program including definitions and pathophysiology of pain this difference was no longer of statistical significance [25]. These results are supported by Järemo et al. [17] arguing the need of a better understanding about chronic pain among the patients since patients with a lower health status had constraining beliefs about their chronic pain.
Moreover, Racine et al. [21] argue that participant bias is one explanation to the sex differences and that there is an overemphasis of measurements showing these differences. Many studies have only controlled the data for sex rather than compared men and women separately [4, 5, 9, 10, 26] which might lead to incorrect results since women are overrepresented. Defrin, Shramm and Eli [23] argue that pain tolerance limit and pain threshold are associated with gender roles and the expectations of these roles. Having the stereotypical “macho” attitude affected women to a longer pain endurance and for both men and women a lesser willingness to report pain and pain sensitivity than those who did not have the attitude.
Among men and women with chronic pain the results of the impact on health status vary [7, 8]
and in one study men with chronic pain reported lower quality of life than women [7]. Dureja et al.
[8] found no sex differences regarding chronic pains impact on daily activities besides from the ability to perform daily chores where men reported less impact. Furthermore, the employment status was more compromised due to pain among men than women. Rustøen et al. [7] also showed no differences between sex regarding how much the pain bothered the participants. Nevertheless, healthy lifestyles behaviours could improve health status or reduce the risk of developing chronic pain [27].
There is a lack of knowledge about the sex differences regarding the impact of CWP on health status as well as health predictors in people with CWP. Society has changed since the ‘90s, and there is a lack of studies on how CWP and health status has developed as well as the health predictors during this time. The results of the current study could increase the knowledge and understanding of the possible differences between men and women regarding CWP’s impact on health status and how to respond to this in health care and treatment. It also lifts the question if women do have worse health status when having CWP. Many studies have either looked at CWP
from a comprehensive age perspective, among elderly or not sex divided, which make the current study of interest.
The aim of this study was to investigate CWP’s impact on health status in women and men of 35- 54 years of age in a sample from the general population. The aim was further to investigate lifestyles predictors for better health status in those with CWP in a 12- and 21-year perspective.
Method
Design and subjects
The present study is a part of a 21-year prospective population-based cohort, the EPIPAIN study [4].
Participants from the EPIPAIN study constitutes a representative sample (n = 3928) from the general population from two municipalities in the southwest of Sweden. Every 18th man and woman at the age of 20-74 years were selected from the computerised Swedish nation population register which is categorised according to date of birth [4].
The present study includes selected participants aged 35-54 years in 1995. Baseline data at 1995 included 975 participants (men/women 442/533) with a 12- (n = 734, 328/406) and 21-year (n = 622, 268/354) follow-up (Fig. 1). Including cross- sectional features at baseline and each follow-up and a 12- and 21-year longitudinal feature regarding health predictors. The age span was chosen since it represents mid-life and is an age before and during when chronic pain becomes more present around the age of 40-50 years [13, 19, 20] and was therefore considered of interest.
Data was collected via a postal questionnaire during the 21 years with follow-ups in 1998, 2003, 2007 and 2016. The follow-ups occurred during other related sub-projects in the EPIPAIN study.
Data from 1998 and 2003 was not used in this study. In 2016, a web-based questionnaire was available, and two reminders were sent out on each occasion.
Questionnaire
The questionnaire consisted of the standard version of the Short-Form General Health Survey (SF-36) [28] and questions about socio- demographic, pain and lifestyle factors [4]. The Swedish validated standard version of SF-36 and interpretation manual was used [29]. The questionnaire has 36 items whereof 35 are
grouped in eight different health concepts, Physical Functioning (PF), Role function – Physical aspect (RP), Bodily Pain (BP), General Health perception (GH), Vitality (VT), Social Functioning (SF), Role function – Emotion aspect (RE) and Mental Health (MH). Each health concept has a scoring from 0-100 where a higher score indicates a better health status [28, 29]. Questions about pain included the experience of the pain and a drawing of a body with 18 predefined regions to localise pain regions. Lifestyles factors measured were personal support, friendship circuit smoking, alcohol intake, physical activity and sleeping habits [4]. The questions remained the same during each occasion except questions regarding alcohol intake and physical activity which were updated in 2007, and physical activity once again 2016 according to the standards from the Swedish National Board of Health and Welfare based on Haskell et al., [30].
Definitions
Pain is defined according to the International Association for the Study of Pain (IASP) as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
[31]. In the soon to be published (summer of 2019) ICD-11, an additional sentence will be part of the definition namely “Chronic pain is pain that persists or recurs for longer than 3 months” [2]. Furthermore, chronic widespread pain (CWP) is defined according to the American College of Rheumatology (ACR), as pain lasting for a minimum of 3 months, present on both sides of the body, below and above the waist and the axial skeleton [11]. The key question “Have you experienced pain lasting more than three months during the last 12 months?” separated the cases with chronic pain. The key question together with the pain drawing of the body was the basis for the three pain categorises used in this study: no chronic pain (NCP), chronic widespread pain (CWP), and chronic regional pain (CRP) if the criterion for CWP was not met. Health status in the present study is not referring to WHO:s ordinary definition of health having a complete state of wellbeing [32], instead, with the Ottawa
documents of health promotion where health is seen as “the process of enabling people to increase control over, and to improve, their health” [33]. Healthy lifestyle refers to behaviours that reduce the risk of illness, early morbidity or increases physical, mental and/or social well-being [34].
Ethics
Written informed consent was collected from all participants and the study adhered with the Helsinki Declaration [35]. The study was approved by the Regional Ethical Review Board, Faculty of Medicine, University of Lund, Sweden (Dnr LU 389-94; Dnr 2016/132).
Statistical analyses
Descriptive statistics were presented at baseline in 1995. Variables analysed were age, gender, education level, social support, friend circuit, smoking habits, alcohol intake, physical activity, sleeping habits, the SF-36 eight subscales and, the different pain groups NCP, CRP and CWP.
Analyses were performed separately.
Differences in CWPs impact on health status was measured via SF-36 using the Swedish manual [29]. Differences in mean score in the eight sub-categories in SF-36 at baseline and the follow-ups were compared by independent samples t-test. NCP and CRP were forming one group compared to CWP, and sex differences
