Influence of psychological status on back pain and clinical assessments in Chinese ankylosing spondylitis patients: a cross-sectional study

Objective: To evaluate the influence of psychological status on back pain and clinical assessments in ankylosing spondylitis (AS) patients. Methods: Three hundreds and Fourteen AS patients were enrolled into the study. Self-rating anxiety Scale (SAS), Self-Rating Depression Scale (SDS), pain-visual analogue scale (VAS), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and Functional Index (BASFI), and Metrology Index (BASMI), fingertip-to-floor distance, were used to assess psychological and clinical characteristics respectively. Results: SAS and SDS scores were significantly higher than normative values of Chinese population (P=0.000). Back pain, BASDAI and BASFI were positive correlated with anxiety and depression (P<0.05), while BASMI and fingertip-to-floor distance were not correlated with them (P>0.05). Anxious and depressed patient subgroups had significantly higher levels of back pain, BASDAI and BASFI than non-anxious and non-depressed subgroup (P<0.05). No statistical difference was found with BASMI and fingertip-to-floor distance (P>0.05). In hierarchical multiple regression analysis, the psychological variables contributed significantly to the variance in back pain scores, adding an additional 8.7% to the overall R-square beyond that accounted by demographic variables (R-square 6.3%), resulting in a final R-square of 19.4%. Multiple stepwise regression analysis revealed that anxiety was the second statistical contributor to C-reaction protein in predicting back pain (standardized coefficients of 0.018). Conclusion: Anxiety and depression have a considerable effect on back pain and self-reported clinical assessments in Chinese AS patients.