Responsiveness of central sensitization-related measures in older people with chronic low back pain

To determine the responsiveness of central sensitization measures, Conditioned Pain Modulation (CPM) and Central Sensitization Inventory (CSI), in older adults undergoing an exercise program and to compare their responsiveness with outcomes measures of pain and disability.

This is a prospective registered (RBR-2qyc425) responsiveness study with a pre-post interventional study design.

People aged 60 years and over with chronic non-specific low back pain were recruited. Demographic and clinical data were collected before and after an 8-week group exercise program. The CSI, CPM test, pain intensity and disability were collected at baseline and post-intervention. The Global Perceived Effect scale was collected post-intervention. Responsiveness was determined by calculating effect sizes, standardized response mean (SRM) and the area under the receiver operator curve (AUC). We also conducted subgroup analyses to investigate the responsiveness of these measures in participants classified as: recovered versus not recovered, CPM-efficient versus CPM-inefficient and as having high versus low CSI scores.

118 participants completed the study. Pain and disability were the most responsive measures (effect sizes and SRM >0.7), followed by CSI (effect size and SRM >0.3). The CPM measures were not responsive. Pain and disability were also more responsive in identifying those participants who recovered after treatment (AUC >0.70) compared to CSI and CPM measures (AUC< 0.70). In addition, CSI showed a moderate to good correlation (0.52) with disability and little or no correlation (0.24) with pain. The CPM measures showed little or no correlation with pain and disability. Our subgroup analyses showed that CSI and CPM may be more responsive in patients with higher baseline CSI scores and those classified as CPM-inefficient, respectively.

Current measures of central sensitization are not as responsive as clinical outcomes of disability and pain. Central sensitization measures should not be used to monitor improvement with exercise intervention in older adults with non-specific low back pain. Future studies investigating the responsiveness of these measures in more precisely defined subgroups and using contemporary operational definitions are warranted.