The association between patients' illness perceptions and longitudinal clinical outcome in patients with low back pain.

Introduction: Illness perception is suggested to influence outcome in patients with low back pain (LBP). It is unknown if specific illness perceptions are of more importance for longitudinal outcomes, including development of self-management strategies. Objectives: This study explores whether patients' initial illness perceptions were associated with disability, pain, health-related quality of life, and self-care enablement outcomes in patients with LBP after 3 and 12 months. Methods: Four hundred sixty-seven consecutive patients seeking physiotherapeutic primary care for LBP were eligible to participate in this prospective cohort study, providing data at baseline and after 3 and 12 months (mean age 45 years, 56% women). Multiple linear regression analysis was used to explore whether patients' illness perceptions at baseline were associated with outcome in the Oswestry Disability Index (ODI), Numeric Rating Scale-LBP (NRS-LBP), EuroQol Five Dimensions, and Patient Enablement Instrument (PEI). Results: Stronger beliefs that the back problem will last a long time at baseline were associated with worse outcome in ODI, NRS-LBP, and PEI at 3 and 12 months and in EuroQol Five Dimensions at 12 months. Negative beliefs regarding treatment's ability to improve LBP were associated with worse outcome in NRS-LBP and PEI at 3 and 12 months and in ODI at 12 months. Conclusions: Illness perceptions regarding prognosis and treatment's ability to improve symptoms were the most prominent perceptions explaining several longitudinal clinical outcomes. These expectations should be addressed in an early stage in the delivery of interventions for LBP. These expectations were also important for patients' development of coping and self-management strategies.