Background & Aims
Chronic low back pain (CLBP) is most prevalent and debilitating among older adults. Despite the disproportionate burden of CLBP in this population, the biopsychosocial factors driving persistent LBP in older adults remain poorly understood. Central sensitization to pain (CS), which can be approximated by quantitative sensory testing (QST), has been increasingly recognized as a contributor to CLBP in young and middle-aged adults. However, CS has sparsely been examined in older adults, including the extent to which CS is present with aging and comparatively heightened in older adults with CLBP. Therefore, the aim of this preliminary investigation was to distinguish gradations of CS with aging and CLBP by utilizing multimodal QST to stratify pain sensitivity across older adults with CLBP as well as pain-free older and younger adults. The hypothesis was that older adults with CLBP would demonstrate the greatest pain sensitivity, followed by pain-free older and younger adults, respectively.
Methods
This case-control study utilized two testing sessions (between 2-7 days apart) and included 25 individuals in each of three groups (n=75): older adults with CLBP (60-85 years) as well as pain-free older and younger adults (18-35 years). CLBP was defined as pain intensity ?3/10 that persisted for >3 months and occurred on most days in the last 6 months. Static pain sensitivity (i.e., pressure pain thresholds [PPT], heat pain thresholds [HPT], fixed mechanical pain [FMP], and fixed cold pain [FCP]) and dynamic pain sensitivity (i.e., thermal ramp and hold [RH], heat pain aftersensations [AS], mechanical temporal summation [MTS], and conditioned pain modulation [CPM]) were quantified at both testing sessions, with the order of tests in each domain randomly counterbalanced between sessions. Means for pain sensitivity responses were averaged across sessions. Group differences in pain sensitivity were assessed with a multivariate analysis of variance test (MANOVA).
Results
The MANOVA revealed a main effect for group (F (16, 130) = 5.079, p < .001; Wilk's ? = 0.345, partial ?2 = .413). For static pain sensitivity measures, only FCP was statistically different between groups (F=6.562, partial ?2 = 0.154, p=0.002), with post hoc analyses indicating that older adults with CLBP had elevated FCP sensitivity compared to younger adults (p<0.001). In turn, every dynamic pain sensitivity test was different between groups (RH: F=3.283, partial ?2 = 0.084, p=0.043; AS: F=8.039, partial ?2 = 0.183, p<0.001; MTS: F=6.361, partial ?2 = 0.15, p=0.003; CPM: F=16.041, partial ?2 = 0.308, p<0.001). Older adults with and without CLBP demonstrated elevated pain sensitivity responses during AS, MTS, and CPM compared to younger adults (all p’s<0.05). For RH, older adults with CLBP exhibited less pain sensitivity than younger adults (p=0.012), which may stem from the self-selection of statistically lower thermal stimulation temperatures in the CLBP group (F=11.31, p<0.05).
Conclusions
This study provides preliminary evidence for heightened static and dynamic pain sensitivity in older adults with and without CLBP compared to pain-free younger adults, suggesting that CS with aging may occur through impaired endogenous pain modulation. Future work is needed to elucidate whether CS (as indexed by pain hypersensitivity) mediates CLBP development and persistence in older adults, and to determine if CS negatively impacts the trajectory of function and disability in older adults with preexisting CLBP.
References
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Presenting Author
Patrick Knox
Poster Authors
Topics
- Specific Pain Conditions/Pain in Specific Populations: Low Back Pain