Table 2

INCIDENCE measures, variable- oriented hypotheses
Research question Outcome Method of analysis Results from the model data set
All respondents, n = 244 Highly compliant respondents, answering 80% (≥15/18 weeks), n = 161
3A: Incidence during the full study period for the whole sample and for subgroups Recovery, i.e. reporting 0 or 1 pain days in 2 consecutive weeks = Event Time to event analysis, with Kaplan Meier curves. Log rank test for differences between groups Illustrated in Figure 2. Logrank test for effect of previous duration: p < 0.001 Logrank testfor effect of previous duration: p = 0.002
3B: Incidence for the full study period in relation to the selected predictive variables Recovery, i.e. reporting 0 or 1 pain days in 2 consecutive weeks = Event Time to event analysis with a) Cox proportional hazard regression or b) Discrete hazard regression Hazard ratio (HR) showing recovery, long duration reference, estimate and 95% CI: a) 1.95 (95% CI: 1.4-2.6), b) 2.03 (95% CI: 1.5-2.7). Hazard ratio (HR) showing recovery, long duration reference, estimate and 95% CI: a) 1.95 (95% CI: 1.4-2.6), b) 2.03 (95% CI: 1.5-2.7).
3 C: Time point for an event during the pain course The time point of change in the course of pain = Event Spline regressions, the event defined as the intersection of linear regression lines (the knot). Short duration: knot at 4.5 weeks Long duration: knot at 5.9 weeks Short duration: knot at 4.4 weeks Long duration: knot at 5.8 weeks

Axén et al.

Axén et al. BMC Medical Research Methodology 2012 12:105   doi:10.1186/1471-2288-12-105

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