Prognostic factors of prolonged disability in patients with chronic low back pain and lumbar degeneration in primary care: a cohort study

Study design: A cohort study with 1-year follow-up.

Objective: To identify prognostic factors in patients with chronic nonspecific low back pain (LBP).

Summary of background data: The factors (e.g., sociodemographical, low back-related, radiological, and biological) associated with persistent pain and disability for patients with chronic nonspecific LBP are uncertain. Furthermore, sparse information exists about the relationship between biological factors like impaired fasting glucose tolerance and chronic nonspecific LBP.

Methods: The participants consisted of 250 patients with nonspecific LBP of more than 6 months duration and degenerative lumbar osteoarthritis. The patients were originally recruited for a randomized controlled trial from the clinics of general practitioners, physiotherapists, and chiropractors. Potential predictors were evaluated at baseline. The outcome was absolute level of pain-related disability (Roland-Morris Disability Questionnaire [RMDQ]) at 1 year. The association between potential prognostic factors and the outcome was analyzed with multivariate linear backward regression.

Results: At baseline and 1 year, the RMDQ scores were 9.5 and 5.1 points, respectively. Mean (SD) baseline values for body mass index (BMI), EuroQol (EQ)-index, EQ-visual analogue scale were 25.4 (4.3), 0.60 (0.3), and 61.2 (20.8), respectively. Higher pain-related disability levels (1-year RMDQ score) were associated with 6.1 mmol/L or more fasting glucose level at baseline (β, 3.7; 95% confidence interval [CI], 1.2-6.1; P = 0.00), baseline pain-related disability (β 0.2; 95% CI, 0.1-0.4; P = 0.00), BMI (β, 0.2; 95% CI, 0.1-0.3; P < 0.03), EQ-index (β, -4.5; 95% CI, 6.9 to 2.1; P = 0.00), and EQ-visual analogue scale (β, 0.3; 95% CI, -0.6 to -0.0; P = 0.03). However, a limited number of patients had 6.1 mmol/L or more of fasting glucose level at baseline (13/250 patients). The imaging findings, modic changes, and high intensity zones had no predictive ability.

Conclusion: Increased pain-related disability at 1 year was seen in patients with impaired fasting glucose tolerance, greater pain-related disability, higher BMI, and lower quality of life at baseline.