Pain in the three spinal regions: the same disorder? Data from a population-based sample of 34,902 Danish adults

Traditionally, studies on non-specific back pain are focused on a single spinal region, such as low back pain (LBP), mid-back pain (MBP) or neck pain (NP). This approach may be based on the assumption that pain in different spinal regions are distinctive entities and that the prevalence and characteristics of pain in each of the three major regions vary considerably. The majority of studies are focused on LBP, as it seems to be the most prevalent spinal disorders, followed by NP, whereas far fewer studies are dealing with MBP. Recently, however, the idea that non-specific back pain is a site-specific disorder has been challenged, suggesting that localized musculoskeletal pain should be seen as part of a more general musculoskeletal syndrome [1, 2].

Several arguments support this suggestion: First, there is a large degree of co-occurrence in musculoskeletal diseases, as a large proportion of people with musculoskeletal problems have pain in more than one site [1, 3‐7]. Second, many of the non-specific musculoskeletal pain syndromes share common factors with each other [2, 5, 8, 9]. Third, the one-year transition pattern of reported pain has been noted to be fairly similar in different spinal regions [10]. Finally, the genetic contributions of pain in different spinal regions are fairly consistent, which suggests that there may be a common genetic basis for back pain in general. All these facts suggest that pain in different spinal regions should not be regarded as separate disorders but rather that back pain - regardless of location - may be a single entity.

In order to determine if back pain is a single entity or not it would be necessary to compare the different regions with each other using a large population-based cohort. However, such studies are lacking as most studies report only single spinal regions. The objective of this paper is therefore to report on the patterns of non-specific pain in each of the three spinal regions and their consequences in order to determine the degree of similarity or difference between the regions.

The results of this study demonstrate that although LBP is the most prevalent complaint in the general population, the relative proportions of people with back pain, including radiating pain, and the relative proportions of people reporting consequences thereof, are similar in all three spinal regions. It is particularly interesting that the relative percentage of people with pain in a spinal region, who also report to have had radiating pain from that particular region, is almost identical despite anatomical, functional and symptomatic differences in the three regions.

Our findings suggest that there are no obvious or unique pain patterns for individual spine regions, at least not on the variables that we studied. Rather, these similar pain patterns may reflect a general expression of pain and if this is correct then this distribution may also be found in other musculoskeletal pain syndromes. A literature search revealed two Nordic studies of the general population, in which pain data could be extrapolated in a similar manner. In the first study, based on 850 adults from Iceland [19], pain in the past year and in the past week were reported for the neck, upper back, and low back, and all major joints in the body. The proportions of people who had experienced pain in the past week out of those who reported to have had pain in the past year were remarkably similar (about 50%) for six of their nine musculoskeletal sites. In the second study, based on 46,901 Norwegian adults [20], the duration of pain in the past month was reported as < 15 days for about 1/3 of the study sample, regardless if pain was noted for the neck, upper back or low back. The same proportion was found also for the hips, knees, ankles/feet, elbows, and wrist/hands.

We also found similarities in relation to the consequences of back pain. For all three regions of the spine, slightly more than half of those who had experienced pain during the past year also reported some type of consequence of the pain. The majority reported one or two consequences, which were typically care-seeking or reduced physical activities. Regardless of the region and duration of the pain, the hierarchy of consequences was remarkably similar. Although, the hierarchy of the five consequences demonstrates a logical preference of choices for any musculoskeletal pain, it is nevertheless striking how the relative proportions are almost identical for the three spinal regions even with longer pain durations. This, too, indicates that the pattern of reactions may have some common mechanisms or expressions based on similarity in the condition or a similarity in how people react to spine-related pain regardless of where it hurts.

Despite the obvious similarities for all three spinal regions, some variations were noted. In particular, LBP resulted in relatively more consequences compared to MBP and NP. This is in accordance with other studies, in which especially sick-leave and care seeking are more commonly reported in people with LBP [19]. These findings indicate either that problems in the lumbar spine affect people's life more than problems in the neck/mid back or that there is a subgroup of people with LBP, who have a different type of condition, and that this type of LBP creates more problems than non-specific pain in the neck or the mid back.

Remarkably similar patterns in pain reporting and its consequences of pain were noted for the three spinal regions. We therefore propose that, at least in a general population, back pain in terms of its relative prevalence and consequences may be regarded as the same condition regardless of where the pain happens to manifest itself. However, some exceptions were noted, particularly in relation to pain in the lumbar spine and further studies are needed to confirm our main results.