Consequences of Chronic Non-Cancer Pain in adulthood. Scoping Review.

ABSTRACT OBJECTIVE To examine and map the consequences of chronic pain in adulthood. METHOD Documents addressing the impact of chronic pain on the psychological and social spheres of people suffering from chronic pain, published in Spanish and English between 2013 and 2018, were included. Those who addressed pharmacological treatments, chronic pain resulting from surgical interventions or who did not have access to the full text were excluded. Finally, 28 documents from the 485 reviewed were included RESULTS Studies show that pain is related to high rates of limitation in daily activities, sleep disorders and anxiety-depression spectrum disorders. People in pain have more problems to get the workday done and to maintain social relationships. Chronic pain is also associated with worse family functioning. CONCLUSIONS This review shows that limitations in the ability to perform activities of daily living, sleep, psychological health, social and work resources and family functioning are lines of interest in published articles. However, knowledge gaps are detected in areas such as the influence of having suffered pain in childhood or adolescence, the consequences of non-fulfillment of working hours and gender inequalities.


INTRODUCTION
Pain is an unpleasant sensory and emotional experience that acts as a sign of biological alertness in the face of real or potential tissue damage 1 . It can be classified according to etiology, anatomical location or duration 2 . According to the latter, chronic non-cancer pain (CNCP) persists continuously or intermittently for a period of more than three months and is not associated with cancer processes 3 .
CNCP is considered a public health problem that affects 20% to 35% of the world's population 4 , 19% of the European population 5 and 17% of the Spanish population 6 . When pain persists for long periods of time, it loses its protective purpose 7 and becomes the result of a complex process in which biological, psychological and sociocultural 8 factors interact with each other 9 . Several international organizations, such as the European Pain Federation or the International Association for the Study of Pain, consider that a change of perspective in the assessment and treatment of pain is necessary, being addressed as an entity in itself 10 , in which the family, social and cultural context that the person lives is considered 11 .
In the last ten years, scientific production on the repercussions of pain has increased. Numerous studies state that the perception and appreciation of CNCP affect sleep 12 or limitations of daily activity 13 , but also psychological and social factors such as anxiety, depression 14 , self-esteem 15 , coping 16 , resilience 13 , social and family support 7 and/or use of toxic substances 14 .
Therefore, we consider it necessary to know the individual and social consequences that CNCP has on the adult population. For this, we conducted a Scoping Review of the scientific literature. Our goal is to examine and map the consequences of chronic pain in adulthood.

METHODS
The Scoping Review methodology is used to map the scientific literature and detect areas of study that are not sufficiently researched 16 . To accomplish this, we used the methodological framework proposed by Arksey and O'Malley 17 and the Joanna Briggs Institute Reviewer's Manual 18 . Although the Scoping Review methodology does not require quality assessment, several authors consider it a strength 19 , as it allows to make recommendations for clinical practice 20 .
In view of these considerations, we assessed the level of evidence (LE) and the degree of recommendation (DR) of the studies included in accordance with the Scottish Intercollegiate Guidelines Network 21 . In this case, LE and DR scores are related. Thus, for an investigation with NE 1++; 1+ or 1-is considered extremely recommended (DR A); for NE 2++, 2+ or 2the recommendation rating would be favorable (DR B), and for LE 3 and 4 the degrees of recommendation would be favorable, but not conclusive (DR C), and it is not recommended or disapproved (DR D), respectively. consequences of chronic non-cancer pain; (2) in adults between 18 and 65 years old, not hospitalized; 3) published between 2013 and December 2018 and 4) written in Spanish or English.
Exclusion criteria were: 1) documents dealing with pharmacological treatments; 2) documents that address people with chronic non-cancer pain resulting from neurodegenerative diseases, chronic infectious diseases or cognitive impairment and 3) documents that did not have access to the full text.

Screening
After the removal of duplicate articles in the research, the selection process was performed, evaluating the relevance of the studies identified. This process was performed by two reviewers independently.
In the first phase, reviewers assessed the titles and abstracts found to exclude articles that did not meet the inclusion and exclusion criteria. Later, they reviewed their contents in full text and decided which ones were included in the data extraction phase. In case of disagreement about the inclusion of an article between the two reviewers, it was discussed with the rest of the research team until consensus was reached.

Data extraction and analysis
Team members produced a document that served as a model for the extraction of information from the article to be standardized. In addition, they developed a protocol to systematize the work procedure. Two of the team members independently collected information about each of the articles (authors' names, year and country of publication, study objective and methodology, sample size and characteristics, intervention, main results obtained and key points). All team members discussed the information in cases of disagreement until consensus was reached.

RESULTS
After the review, 485 articles whose titles met the inclusion criteria were obtained. The search for gray literature produced 60 documents. Once duplicates were removed, 285 titles and abstracts were reviewed using the inclusion and exclusion criteria. Exactly 170 full texts were recovered for screening. After reviewing the full texts, 142 were excluded, because they did not report the theme of the study, remaining 28 documents for analysis ( Figure). The studies included were classified into four areas based on the effects of chronic pain: activities of daily living (ADL); sleep (S); psychological health (PH) and socio-labor and family consequences (SLFC) (Table).

Consequences on everyday activities
Chronic Non-Cancer Pain increases in disability and limitation in daily activities [22][23][24][25][26] . People tend to avoid activities that cause or increase the severity of pain, leading to a decrease in activity levels compared with healthy people [22][23][24]27 . In this sense, when pain interferes with the ability to perform daily activities, people tend to show a negative perception of themselves due to lower physical capacity and misunderstanding of people in their environment 28 , a fact that translates into greater catastrophizing in the face of pain 29 . In turn, studies indicate that people with CNCP spend more time sitting and less time standing, and that an increase in physical activity during the afternoon is related to the decrease in activities of daily living in the evening 30 .
A less active lifestyle is also associated with persistence and more severe pain levels 31 , comorbidity of chronic diseases such as obesity or diabetes 30,32 , more difficulty in self-care and increased use of health services 33 .

Consequences of sleep
Sleep problems are a common consequence in people with CNCP 29 . Studies suggest pain management improve sleep quality by up to 14%. The results indicate there is a circular and dynamic interrelation in which pain causes sleep disorders, which, in turn, increase pain intensity [34][35][36] .
Other studies state that between 50 and 88% of people meet the diagnostic criteria for sleep disorders 36,37 and have abnormal brain activity during sleep 38 . In a study conducted by Cranford et al. 37 , it was reported that 30% of the participants had sleep problems every night and/or several times a night. The most common changes are difficulty in starting or maintaining sleep, waking up earlier, having fragmented or no-restorative sleep 34 , and higher levels of fatigue during the day; more evident symptoms in women than in men 38 .
Sleep disorders due to CNCP are also related to limitation in performing daily activities and disability 34 . Andrews et al. 4 noted that people performing more intense activities during the day suffer more pain and stay awake longer periods at night.
On the other hand, some people resort to using cannabis to improve the quality of their sleep. Cranford et al. 37 found that 80% of study participants responded to having used cannabis in the last six months to improve the quality of their sleep, showing a positive opinion about them. However, in 65% of cases people have developed cannabis dependence.

Consequences on psychological health
CNCP is associated with suffering from mental illness 4 . Different studies have investigated this relationship, finding that mental illnesses are present in 75.3% of cases of pain 4,14 , and     anxiety and depression rates reach 30-40%, being more pronounced in women 13 . Anxiety and depression cause fear of pain-enhancing activities, generating a spiral of pain, fear and avoidance 24,[39][40][41][42] .
Several authors highlight the relationship between adaptability and CNCP experiences. Thus, people with higher self-esteem have much less unpleasant pain stimuli, improving the use of coping strategies 43,44 . The findings of El-Shormilisy et al. 45 suggest that coping is also mediated by sex. Women with CNCP develop fewer adaptation strategies than men, resulting in worse functional outcomes.
On the other hand, the prevalence of suicidal ideation and suicide attempts in the population with CNCP is 20% and 5 to 14%, respectively, twice the general population 3,45-47 . According to Campbell et al. 3 , this relationship may be due to many people who do not reduce the intensity of their pain, despite undergoing lifelong treatment.
The relationship between CNCP and tobacco use is also complex. According to Orhurhu et al. 14 , 25.3% of people with CNCP use tobacco, twice the general population. A study by Dirtre et al. 48 found that 43% of participants who used tobacco also had CNCP. These people reported tobacco use as an agent who calmed anxiety caused by pain. In this sense, the relationship between CNCP and tobacco use is dynamic. Smokers have higher pain rates, increased number of painful sites and higher levels of anxiety and depression, which would encourage tobacco use 14,48 . Thus, pain would strengthen tobacco dependence that results in greater pain 48 .

Socio-employment and family consequences
Several studies have shown CNCP causes social isolation, decreased leisure activities and work difficulties 20,23,47 . However, people who have greater social participation may have better health, reduced anxiety, depression and reduced perceived stress 23,24 . In this sense, El-Shormilisy et al. 11 , claim that women and men with CNCP are differently related to their social environment. According to this author, women are socialized from an early age to express their emotions and seek social support, and men would be more likely not to do so. This could translate into greater resources to deal with the CNCP in them.
In the field of research, the existence of CNCP poses a great economic burden for the individual and the system. According to Dany et al. 48 , most people need to keep working despite the pain, especially in these groups with fewer resources, and they may have less productivity at work.
The family environment of people with CNCP may also be affected 24 Cross-sectional study. N=1,764 people • EuroQol-5D (EQ-5D) The prevalence of pain in workers was higher than in workers. Women had more severe depressive symptoms than men.  from other members can trigger different types of invalid responses, rejection, and/or support 22 . In this sense, difficulties with the partner contribute to increased depression and anxiety 50 .
Regarding parental relationships, parents model the perceptions and attitudes of their sons and daughters in the face of pain through their own experience, taking as an example the actions and discourses they observe. In turn, pain may affect parents' ability to complete physical tasks related to creation 49 .

DISCUSSION
The increase in scientific production on chronic pain in adulthood allowed us to characterize aspects of interest and detect new lines of research, despite having this Scoping Review as the main limitation of linguistic bias, since there were no studies published in languages other than Spanish or English.
This review shows the ability to perform activities of daily living, sleep, psychological health, labor socio-economic consequences and family functioning are lines of interest in articles published. However, knowledge gaps are detected in areas such as consequences of work, toxic consumption and gender inequalities.
There is an extensive literature on the impact of CNCP on functional capacity, but comorbidity with other chronic diseases is less known. Butchart et al. 51 , found that about 30% of people with coronary heart disease and chronic obstructive pulmonary disease (COPD) also suffer pain. Torrance et al. 52 state that comorbidity between chronic pain and one of these two diseases increases by up to three times the probability of dying compared with the population who do not suffer from pain. These authors explain this relationship as a result of the decrease in the daily functioning capacity of people with CNCP. These higher rates of comorbidity, mortality and dependence result in greater use of health services and, therefore, economic expenses, as found by Pitcher et al. 31 , in our results. However, few studies produce actual figures on the real economic impact of CNCP. Direct and indirect costs in Europe are estimated at 200 million euros and in the US between US$560 million and US$635 million 54 .
As to psychological health, numerous authors have found that the condition of mental illness, such as anxiety or depression in people with CNCP, is common. Knowing this relationship is important, because authors such as Rayner et al. 55 report that an effective approach and treatment of depression and anxiety in people with CNCP can improve their health by up to 14%, reducing thus functional limitation and impact on health systems. On the other hand, other authors consider this relationship inverse, that is, chronic pain would be one of the first consequences of mental illness [56][57][58][59] . However, for authors such as Von Korff et al. 60 , the temporal relationship between mental illness and CNCP is unclear, it seems to be bidirectional and both act as a positive reinforcement for the other.
People with CNCP have higher rates of tobacco use. In our results, authors such as Catalano et al. 13 and Ditre et al. 48 affirm that tobacco habit increases the level of pain. However, Shi et al. 61 observe that this relationship has not been shown, but they insist that depressive symptoms associated with tobacco use can increase pain levels.
No studies on the relationship between chronic pain and alcohol consumption were found. We consider it necessary to conduct research on this subject considering the results obtained by Riley & King 62 in 2009, in which they show that alcohol may be used to relieve pain by its transient analgesic effect. Some results contradict the Danish cohort study by Ekholm et al. 63 , concluding that patients with CNCP are less likely to consume alcohol, but it is risky when mixed with the drug 64 .
Regarding labor consequences, the loss of work and the economic cost that generates pain are little studied. Yamada et al. 65 claim that people with CNCP may have lower productivity rates, which would be a heavy economic burden. In this sense, Pain Proposal's results support this statement, adding that 21% of the population with CNCP felt unable to finish their working day, which translates into an impact on the labor market of 2.5 million euros and 52 million of lost working days per year 10 . They also indicate that in Spain, the average number of days lost due to pain is 16.8 days a year 66 .
Regarding gender inequalities, research shows that, as in other clinical pathologies, women receive more precarious health care than men 67 . Several studies have found great differences in subjective perception of pain or general well-being in women, despite having scores similar to those of men in analytical and radiological data, which may lead us to think that it is devaluing itself with the use of clinical indices that do not reflect the women's reality. In addition, the authors emphasize the importance of gender analysis in the study of CNCP 68 . In this review, the studies found prevalence data disaggregated by sex, and some, in a transversal way, identify differences in male and female experiences, but do not analyze them from a gender perspective 69 .