Pain prevalence and its determinants after spinal cord injury: a systematic review

Pain prevalence studies are important as they illustrate the magnitude of pain problems in a certain patient population, such as patients living with a spinal cord injury (SCI). Strikingly, reported pain prevalence rates in SCI patients are found to vary greatly, while determinants for the differences between pain prevalence reports remain unclear. We here aim to identify determinants for the differences (heterogeneity) in pain prevalence reports through a systematic review of all SCI pain prevalence reporting studies. Literature search was done using Medline, Cumulative Index to Nursing and Allied Health Literature, ISI Web of Knowledge and Embase. Data abstraction was performed while blinded and was followed by meta-(regression)-analyses. We identified 82 studies. Study design-related determinants of SCI pain prevalence reports were pain definition strictness (mild, moderate or high), primary study goal (pain study or not), data source (retrospective or not), and in a limited number of cases response/attrition rates. While correcting for these items, population characteristics correlating with pain prevalence rates were both proportion of patients with a depression and average time after injury (positive correlations). Between-study heterogeneity may remain even after the identification/correction of above-mentioned causes of heterogeneity.Pain after SCI does seem to relate to the duration of the injury and depression, yet major causes of bias in reported pain prevalence are found to be related to the primary study goal (pain study or not), choice of pain definition and the use of retrospective data.