Attention demands of postural control in non-specific chronic low back pain subjects with low and high pain-related anxiety.

Impaired postural control in chronic low back pain (CLBP) has been attributed to deficits in sensory and motor functions. However, it is not known if pain-related anxiety affects motor and cognitive function of postural control. The aim of this study was to compare the interactive effects of postural and cognitive function in CLBP patients with high and low pain-related anxiety and healthy subjects. Thirty-eight patients with nonspecific CLBP (19 with low and 19 with high pain-related anxiety levels) and 20 asymptomatic subjects participated. Postural control was assessed by center of pressure (COP) parameters including mean total sway velocity, area, anterior-posterior (A-P), and medial-lateral (Med-Lat) range. Postural task was assessed during four conditions (eyes open with and without ankle vibration-eyes closed with and without ankle vibrations). Participants performed the postural task with or without auditory Stroop task. Average reaction time and error ratio of auditory Stroop test were calculated as measures of the cognitive task performance. Significantly reduced sway area was observed in CLBP patients with high pain-related anxiety and control subjects during the dual-task condition as compared with the single task. In addition, A-P range was significantly reduced in CLBP patients with high pain-related anxiety during dual tasking when eyes were closed with ankle vibration. In addition, only the CLBP subjects with high pain-related anxiety showed significantly longer reaction times by increasing the difficulty of standing postural task. Pain-related anxiety may influence the postural cognitive interactions in CLBP patients. Furthermore, it may be considered as a contributing factor for postural strategies adopted by CLBP patients.