Background
Low back pain (LBP) and neck pain (NP) are common in the general population [
1‐
3] and are of considerable societal costs [
4,
5]. Whereas LBP and NP have been extensively studied, information on pain in the thoracic spine still remains relatively sparse [
6].
Typically, the three spinal areas are studied or reported as separate entities, or as one single entity defined as just "back pain". Hence, only few studies have reported prevalence of pain in all three spinal regions simultaneously in the same population. This makes comparisons difficult as the designs and reporting of the studies differ considerably. Only a few population-based studies have included all three regions and simultaneously reported prevalence estimates for each of the spinal areas separately [
7‐
13]. However, the presence of spinal pain provides only limited knowledge of how it affects the population at large. Of more relevance is what consequences spinal pain may have on people and to what extent they affect people's daily living.
Studies reporting consequences due to spinal pain for all three regions are also scarce. In adolescents, the most common consequences of spinal pain are reduced physical activity, seeking health care, and staying at home for a couple of days [
10,
12]. Similar findings have been found in adults [
8]. Also in Danish elderlies aged 70-102 with NP or back pain, seeking treatment and reduced activities were relatively common [
13].
Thus, it appears that the types of consequences due to spinal pain are fairly similar in different averaged age groups. However, it is not known if or how these consequences of spinal pain change with age as there may be age-related turning points. For example, in adults with LBP, a large Norwegian register-based study on the 1-yr incidence of sick-leave of at least 2 weeks' duration showed a slight but non-significant increase with age [
14], whereas in another Norwegian population-based study, the 1-yr prevalence of long-term sick-leave due to LBP increased significantly from 5% in the 20-22 yr olds to 24% in the 60-62 yr olds [
15].
Generally, women are overrepresented in the reporting of musculoskeletal pain [
16] and potentially at greater risk of suffering from more consequences of pain compared to men. For example, in Norway and Sweden women were almost twice as likely as men to obtain a disability pension for musculoskeletal disorders [
14,
17]. In addition, a Danish study of older twin individuals showed that women with NP were more likely than men to reduce their physical activity and to seek health care [
13].
It thus becomes apparent that the various consequences of pain in different spinal regions may have a significant socioeconomic burden to the society at large. However, there is still a need to further elaborate on the previous findings for all spinal regions, in particular for the thoracic region, as very little is known about the consequences of having a painful thoracic spine. It is also not known if pain in the different spinal regions result in different consequences, as only few studies [
8,
10] on consequences of all three spinal regions have been conducted. In addition, as some differences in consequences have been noted between adolescents and adults as well as between men and women it is relevant to investigate further how consequences are influenced by age and gender in all three spinal regions.
The purpose of this study was therefore to describe the prevalence of consequences in relation to age and gender for pain reported in the lumbar, thoracic and cervical regions in a large Danish population, representative of the general population.
Discussion
General findings
As expected, spinal pain does not lead to any consequences for most people. Thus, most people with spinal pain seem to manage quite well, either because the pain intensity is only mild or because they have sufficient coping strategies. Still, even if most people do not report more common consequences such as sick-leave because of pain it is not known how they are affected on a daily basis. For instance, persons with back pain are known to turn up at work where they may not perform as well as what they would normally do [
22].
Given that almost two-thirds of people with spinal pain do not report any of the five consequences it may suggest that spinal pain is not an important public health problem. However, even if only a third of spinal pain sufferers report some kind of consequence it would still have a significant impact on the health care system as more than half of the study sample reported some kind of spinal pain within the past year. In addition to this, any sick-leave, even if only for shorter durations, along with reduced daily activities, may result in substantial indirect costs to society.
Among those who did take action, the most common consequences were care-seeking and reduced daily activities. In Danish school-children, seeking health care was also more common than reduction in physical activities [
10]. In Danish elderly individuals aged 70 or more, care-seeking is also more common than reduction of physical activities [
13]. This may indicate that there is a subgroup of people who rely more on external assistance than on their own strategies and hence take action when they have spinal pain.
The health care system in Denmark is either available free of charge or is to a large extent reimbursed. Therefore, it would be tempting to think that the hierarchy of consequences found in this study is typical of what people with back pain would do if medical treatment is free of charge and also, as in Denmark, if unemployment is not a major issue. However, a similar hierarchy of consequences was found also in a Swedish study [
23], despite differences between the countries both on the fee structure and unemployment rates. We are unaware of any other similar hierarchical studies conducted in non-Nordic countries thus, making it difficult to compare these hierarchal trends to socio-economic factors.
Differences were noted between the three spinal regions. Not surprisingly, consequences due to LBP were generally more commonly reported than for any other spinal pain site mainly because more individuals suffered from LBP. However, even when the relative frequencies were calculated, reduced physical activity, sick-leave and change of work remained significantly higher for individuals with LBP compared to MBP and NP. Thus, it seems that LBP has a greater impact on daily living and that individuals with LBP have slightly different coping strategies compared to those with MBP or NP.
In relation to age
We have previously shown that spinal pain is fairly evenly spread over all ages, with no obvious increase in prevalence towards the elderlies [
7]. Still, given the general age-related degenerative spinal changes an accumulation of various consequences in the older age groups would be expected. One could therefore assume that the more serious consequences, i.e. longer sick-leave, change of work, and disability pension would occur mainly in older people and that these would be preceded by reduced physical activities, care-seeking and shorter sick-leave in the younger age groups. However, this was only partly demonstrated in our study.
Interestingly, the number of individuals on sick-leave does not increase with increasing age, but rather the duration of sick-leave increases. Thus, it may be that those individuals who suffer from spinal pain at an earlier age will get worse over time in terms of pain intensity and/or because their general capability to cope with spinal pain decreases with age.
Furthermore, in our study no age-related trend in change of work due to spinal pain was noted. This was unexpected as one would normally assume a certain degree of accumulation with age as people "wear down" because of spinal pain. A theory could be that people with spinal pain at an early age may already realise that they need to change work or work duties because of pain. As expected, disability pension was extremely uncommon in the younger people, but it did not increase dramatically in the oldest group.
Admittedly, memory decay could result in artificially low estimates when the denominator related to spinal pain ever (change of work and disability pension). It is therefore possible that the change of work estimate in reality should be higher, whereas this is unlikely for disability.
In relation to gender
Not surprisingly, more women generally report the presence of spinal pain as well as consequences due to spinal pain compared to men. This sex or gender difference in musculoskeletal pain is well documented [
16,
24] and is probably due to biological influences (i.e. hormonal), psychosocial factors (i.e. gender role expectations) or a combination of both factors (e.g. coping/catastrophizing/anxiety) [
24]. It is beyond the scope of this paper to further discuss this separate research area, but the readers are encouraged to read the comprehensive review by Fillingim et al [
24].
Limitations
The strengths and weaknesses of this study have been discussed before [
7], to which should be added that misclassification of our consequence variables is possible, and that this cannot be verified. Under reporting would probably be more likely than over reporting as the 30-page questionnaire is not specifically focused on spinal pain. We have therefore no reasons to believe that we have a specially selected group of individuals with spinal pain in our study. If, however, this is the case the effect the results will probably be biased towards the null, although this cannot be determined.
Future perspectives
While not studied here, other aspects of interest such as similarities and differences between the spinal regions, multiple pain sites, specific spinal conditions, co-morbidities, various psychosocial factors and their interactions need to be further investigated in order to understand the true underlying nature of the consequences of spinal pain.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
All authors read and approved the final manuscript. KOK was responsible for the epidemiologic study. JH, RF and CLY secured funding for the back pain study. CLY and JH formulated the preliminary research questions and designed the spinal pain questionnaire. CLY formulated the research questions for the present analyses. JN analyzed the data and provided the graphical presentations. CLY and RF did the data interpretation. CLY and RF wrote the first draft and all contributed to the final version.