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Table 2 Linear mixed models to estimate change in pain intensity (NRS) over seven days follow-up and the effect of treatment advice (SA = Stay active versus AA = Adjust activity) on this change

From: The effect of the stay active advice on physical activity and on the course of acute severe low back pain

N = 99

Model 1: Change trajectory

Model 2: Effect of treatment advice

Fixed effects in model

Estimate (SE)

p-value

Estimate (SE)

p-value

Day 1 (intercept)

4.9 (0.2)

<0.001

4.8 (0.3)

<0.001

+Stay active advice

-

-

0.2 (0.4)

0.67

Day (β, linear term)

−0.4 (0.04)

<0.001

−0.4 (0.06)

<0.001

+Stay active advice

-

-

0.05 (0.08)

0.52

  1. Fixed effects in models are presented with pain intensity (NRS) as outcome
  2. Model 1 is the estimated change trajectory without the effect of treatment advice. Model 2 includes the effect of treatment advice, where the effect of the Adjust activity is presented first followed by the added effect of the Stay active advice
  3. A first-order polynomial function was used including the linear term (Day) describing a decrease in pain intensity over time (negative values)