Differences in risk factors for flare-ups in patients with lumbar radicular pain may depend on the definition of flare.

Objectives: The objective was to determine whether specific physical activity (PA) or psychological stress factors are associated with different definitions of flare-ups (pain-defined flares [PDFs]: periods of increased pain lasting at least 2 h, when pain intensity is distinctly worse than it has been recently; and non-pain-defined flares [NPDFs]: obviously uncomfortable feelings, such as fatigue, loss of function, or emotional/psychosocial fluctuations, without major fluctuations in pain intensity based on 11-point scales) among people with lumbar radicular pain.

Methods: This was a case-crossover study. Participants with acute or subacute lumbar radicular pain completed serial face-to-face or online assessments for 6 weeks at 3-day intervals to determine whether they experienced sciatica flare-ups (PDF/NPDF) after specific types of PA or psychological stresses.

Results: A total of 152 participants were enroled. There were 597 PDF and 323 NPDF case periods and 800 control periods. The odds of PDFs were increased by prolonged walking and standing, and the odds of NPDFs were increased by prolonged sitting, mental distress, and depressed mood. According to the multivariable analyses, prolonged sitting (OR: 3.0, 95% CI: 1.7-5.5), prolonged walking (OR: 6.2, 95% CI: 3.9-9.9), and prolonged standing (OR: 5.6, 95% CI: 3.3-9.5) were significantly associated with the odds of PDFs, and prolonged sitting (OR: 3.4, 95% CI: 1.8-6.2), mental distress (OR: 6.7, 95% CI: 2.5-17.5), and depressed mood (OR: 5.8, 95% CI: 2.6-12.8) associated with the odds of NPDFs.

Conclusions: Prolonged sitting, walking, and standing triggered the occurrence of PDF. Prolonged sitting, mental distress, and depressed mood triggered the occurrence of NPDF.