Abstract
Despite an elusive pathophysiology, common characteristics are often observed in individuals with chronic low back pain (LBP). These include psychological symptoms, altered pain perception, altered pain modulation and altered muscle activation. These factors have been explored as possible determinants of disability, either separately or in cross-sectional studies, but were never assessed in a single longitudinal study. Therefore, the objective was to determine the relative contribution of psychological and neurophysiological factors to future disability in individuals with past LBP. The study included two experimental sessions (baseline and six months later) to assess cutaneous heat pain and pain tolerance thresholds, pain inhibition, as well as trunk muscle activation. Both sessions included the completion of validated questionnaires to determine clinical pain, disability, pain catastrophizing, fear-avoidance beliefs and pain vigilance. One hundred workers with a history of LBP and 19 healthy individuals took part in the first experimental session. The second experimental session was exclusively conducted on workers with a history of LBP (77/100). Correlation analyses between initial measures and disability at six months were conducted, and measures significantly associated with disability were used in multiple regression analyses. A first regression analysis showed that psychological symptoms contributed unique variance to future disability (R2 = 0.093, p = .009). To control for the fluctuating nature of LBP, a hierarchical regression was conducted while controlling for clinical pain at six months (R2 = 0.213, p < .001) where pain inhibition contributed unique variance in the second step of the regression (R2 change = 0.094, p = .005). These results indicate that pain inhibition processes may constitute potential targets for treatment to alleviate future disability in individuals with past or present LBP. Then again, the link between psychological symptoms and pain inhibition needs to be clarified as both of these factors are linked together and influence disability in their own way.
Highlights
Of all musculoskeletal pain conditions, low back pain (LBP) is the most common, with an estimated worldwide 1-month prevalence of 23.2% [1] and a lifetime prevalence of up to 84% [2]
Some participants who remained in the study had scarce missing values but t-tests comparing disability in individuals with and without missing values showed that those values were all missing completely at random (p = .14)
In the present sample of workers with a history of LBP, significant Heterotopic noxious counter-stimulation (HNCS) hypoalgesia was observed, and the results did not differ from those of the control group. These results are similar to what has already been observed in a previous study using a different protocol to assess pain modulation mechanisms [47]. Even though both groups were similar in terms of mean pain inhibition efficiency, there was a large amount of variability, which has been observed in studies focusing on patients with LBP [25] or other chronic pain conditions [48]
Summary
Of all musculoskeletal pain conditions, low back pain (LBP) is the most common, with an estimated worldwide 1-month prevalence of 23.2% [1] and a lifetime prevalence of up to 84% [2] Such a high prevalence, and the numerous therapeutic interventions used for nonspecific LBP greatly increase the economic costs and burden of this condition on society [3, 4]. The numerous therapeutic interventions used for nonspecific LBP greatly increase the economic costs and burden of this condition on society [3, 4] Since they always live with doubts as to when the episode will strike [5, 6], many individuals with LBP report that their activities are limited and that they consciously make efforts to avoid pain recurrences when they are pain-free, or pain exacerbations when their pain is ongoing [7]. Identifying factors that contribute to disability regardless of these fluctuating pain levels is critical to increase performance and productivity in the workplace
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