Table 4

Robust linear regression analyses. Estimation of differences in sickness absence days over 6 months between UC and UC+MI or UC+SVAI

VariableUnadjusted ITT analysis
Adjusted complete case analysis*
Adjusted primary ITT analysis with imputations*†
Coef. B95% CICoef. B95% CICoef. B95% CI
UC+MI−7.3−‡ 17.9 0.4 −6.6−15.01.8
UC+SVAI9.3‡ 18.5 0.1 9.4‡ 18.0 0.7 −7.0−15.41.4
Sex, male11.2‡3.818.711.8‡4.619.1
Secondary school§2.6−9.614.81.9−9.713.5
Higher education <4 years§2.8−10.316.02.9−9.715.5
Higher education ≥4 years§−11.0−26.94.9−10.3−25.44.8
Meeting or follow-up plan¶−7.2−15.30.9−5.6−13.52.2
Meeting and follow-up plan¶−5.0−14.44.4−3.5−12.65.7
Physical activity 1–2 days**0.7−8.810.11.1−8.110.3
Physical activity 3–4 days**6.5−−4.118.0
Physical activity 5–7 days**8.1−3.319.57.0−4.118.0
Work ability††−3.5‡−5.0−2.1−3.8‡−5.2−2.4
Musculoskeletal health‡‡−0.8‡−1.3−0.3−0.7‡−1.2−0.02
Sickness absence days previous year§§19.5‡13.125.819.1‡12.925.3
  • n, number of participants in analysis (ITT analysis: UC n=171, UC+MI n=169, UC+SVAI n=169, complete case analysis: UC n=158, UC+MI n=157, UC+SVAI n=159)

  • *Multiple robust linear regression analyses adjusted for predefined possible confounding factors.

  • †Values for missing on the independent variables were imputed with multiple imputations by chained equations with 10 imputations. Imputations were not conducted for the five missing outcome values.

  • ‡p<0.05.

  • §Education: dummy variables compared with compulsory education.

  • ¶Follow-up from employer, dummy variables compared with no follow-up.

  • **Physical activity 1 week prior to baseline, dummy variables compared with no physical activity.

  • ††Measured with single question from the Work Ability Index (0–10).

  • ‡‡Measured with the Musculoskeletal Health Questionnaire (0–56).

  • §§Number of days away from work due to sickness absence 12 months prior to baseline, logarithmic transformed variable.

  • Coef., Coefficient.; ITT, intention-to-treat; MI, motivational interviewing; SVAI, stratified vocational advice intervention; UC, usual case management.