Background: Low back pain (LBP) causes more than 2.5 million visits to US EDs annually. Nearly half report persistent pain and functional disability 3 months later. For patients with LBP in the outpatient setting, these poor outcomes are associated with depression. We sought to determine whether a similar relationship exists among patients with LBP in the ED.
Methods: This is a subgroup secondary analysis of 362 patients who presented to one urban ED with LBP and completed a Patient Health Questionnaire depression subscale (PHQ-9) during the index visit and a Roland-Morris Disability Questionnaire (RMDQ) and a 0-10 pain numeric rating scale (NRS) 3 months later. We performed linear regression modeling to determine the association between depression at the index ED visit and low back pain-related functional impairment and pain severity at 3 months, adjusted for age, gender, race, ethnicity, and education. Secondary outcome values were improvement in RMDQ from index to 3 months and change in NRS from 1 week to 3 months.
Results: At the index ED visit, median PHQ score was 0 (IQR 0,4) and median RMDQ score was 22 (IQR 17,24). At one week, median pain score was 6 (IQR 2,8). At three months, median RMDQ score was 5 (IQR 0,23), median pain score was 4 (IQR 0,3), and median change in RMDQ from baseline was -8 (IQR -20,0). After adjusting for potential confounders, patients with a higher baseline depression severity had worse disability (B=0.43, 95%CI=0.27-0.59) and pain (B=0.14, 95%CI=0.08-0.20) scores at 3 months. They also had less improvement in disability scores from ED visit to 3 months (B=0.20, 95%CI=0.03-0.37). There was no association between depression and change in pain score.
Conclusion: Consistent with data from other settings, our study demonstrates that depression during an ED visit for LBP is associated with functional disability and pain scores 3 months later. Future work among ED LBP patients should address this potentially modifiable risk factor.