From acute to chronic back pain: Using linear mixed models to explore changes in pain intensity, disability, and depression

Abstract

<jats:title>Abstract</jats:title><jats:sec id="j_j.sjpain.2017.02.009_s_006_w2aab3b7c51b1b6b1aab1c17b1Aa"><jats:title>Background/aims</jats:title><jats:p>This longitudinal study investigated the pattern of change in pain intensity, disability, and depression in 232 chronic pain patients who were followed up for 2 years since pain onset. Most studies that have investigated changes in these variables over time have used participants who had already been in pain for more than 3 months. Few studies have followed up individuals from the acute phase onward and such studies used traditional statistical methods that cannot identify transition points over time or measure inter-individual variability.</jats:p></jats:sec><jats:sec id="j_j.sjpain.2017.02.009_s_007_w2aab3b7c51b1b6b1aab1c17b2Aa"><jats:title>Methods</jats:title><jats:p>We followed up individuals with chronic pain from pain onset up to 18 months and we examined their pain intensity, disability and depression trajectories using a modelling approach that allows to account for between and within-individual variability. We compared three patterns of change based on theoretical criterions: a simple linear growth model; a spline model with a 3-month transition point; and a spline model with a 6-month transition point. Time with pain was selected as time metric to characterise the change in these variables in the transition from acute to chronic pain. Sex and age differences were also examined.</jats:p></jats:sec><jats:sec id="j_j.sjpain.2017.02.009_s_008_w2aab3b7c51b1b6b1aab1c17b3Aa"><jats:title>Results</jats:title><jats:p>The results showed that the pain intensity trajectory was best represented by the spline model with a 3-month transition point, whereas disability and depression were best explained by linear growth models. There were sex differences at intercept level in all the models. There were age differences at baseline for pain intensity. No sex or age differences were found for the slope.</jats:p></jats:sec><jats:sec id="j_j.sjpain.2017.02.009_s_009_w2aab3b7c51b1b6b1aab1c17b4Aa"><jats:title>Conclusions</jats:title><jats:p>Pain intensity decreased in the first 3 months but underwent no further change. Disability and depression slightly but constantly decreased over time. Although women and older individuals are more likely to report higher pain intensity or pain-related disability in the first three months with pain, no differences by sex or age appear to be associated with the changes in pain intensity, depression and disability through the process of chronification.</jats:p></jats:sec><jats:sec id="j_j.sjpain.2017.02.009_s_010_w2aab3b7c51b1b6b1aab1c17b5Aa"><jats:title>Implications</jats:title><jats:p>Our findings suggest that pain chronification could be considered a continuous process and contribute to the ongoing discussion on the utility of standard classifications of pain as acute or chronic from a clinical point of view. Clinical and intervention decisions based in these standard classifications should consider the differences in the trajectories of pain related variables over time. In addition, this article illustrates a statistical procedure that can be of utility to pain researchers.</jats:p></jats:sec>

How Do Pain-Response Patterns Influence the Course of Acute Low Back Pain? A Longitudinal Cohort Study

“…Our results are consistent with previous descriptions of LBP trajectories, including reports on the natural course of LBP [31][32][33][34]. However, time-averaged reporting for pain and disability does not re ect individual variability [35], as the distinct trajectories of LBP may include a less pronounced pain decrease and the persistence of pain at an overall high level in patients with severe or uctuating pain [31][32][33][34]. Despite the different pain characteristics reported by our patients, the LBP episode assessed in our study was assumed to be non-transient, and while the pain intensity remained at a low level, it may well have in uenced the quality of life of our patients.…”

“…In our patients, pain intensity and disability decreased signi cantly within the rst 8 weeks but remained stable thereafter, until the last follow-up at 26 weeks. Our results are consistent with previous descriptions of LBP trajectories, including reports on the natural course of LBP [31][32][33][34]. However, time-averaged reporting for pain and disability does not re ect individual variability [35], as the distinct trajectories of LBP may include a less pronounced pain decrease and the persistence of pain at an overall high level in patients with severe or uctuating pain [31][32][33][34].…”

“…The absence of the FAR pattern in our patients re ects the fact that major psychiatric illness requiring treatment was among the exclusion criteria. Rather, the rate of self-reported depression among our patients was low, as previously shown for patients in the general population with acute LBP necessitating primary care [32,39]. Indeed, when followed over one year, patients with low pain intensity and good mental health seem to experience an improvement of LBP, whereas the opposite features are associated with persistent highlevel pain [33].…”

Effects of Scrambler Therapy in Patients with Failed Back Surgery Syndromes and Factors Associated with Depression Affecting Pain before and after the Therapy

“…The negative relationship between treatment duration and BDI can be explained by the nonstatic phenomenon of chronic pain. Bendayan et al [ 29 ] found that depression slightly but constantly decreased eventually in patients with acute and chronic back pain. Also, the longitudinal study of depression in patients with spinal cord injury revealed that the prevalence of a probable major depression changed from 22.1% to 20.2% over time [ 30 ].…”

A Reduction in Pain Intensity Is More Strongly Associated With Improved Physical Functioning in Frustration Tolerant Individuals: A Longitudinal Moderation Study in Chronic Pain Patients

“…Medical treatment (i.e., oral drugs and surgery) is the most frequent approach in the management of chronic pain (Turk et al, 2011; Gatchel et al, 2014; Reid et al, 2015), as well as the first-line intervention in pain guidelines (Koes et al, 2010; Sarzi-Puttini et al, 2012; Dowell et al, 2016). While there is evidence to support that medical treatment is effective for pain management (Turk et al, 2011; Finnerup et al, 2015), studies have also indicated that such reductions in pain intensity do not lead to a proportional improvement of physical and mental functioning (Gauthier et al, 2008; Menezes Costa et al, 2011; Bendayan et al, 2017), so it is possible that underlying mechanisms that have shown to contribute to a better understanding of the experience of chronic pain (i.e., psychological factors) might as well influence this relationship.…”