Table 3.

Final multiple linear regression models with the HAQ, SF-12, physical component score (PCS), and mental component score (MCS) as outcome. Explanatory variables that did not reach statistical significance in any of the models were excluded from the table. Number of observations = 2776.

GroupExplanatory VariablesHAQPCSMCS
ßpßpßp
DemographyWomen0.27< 0.00100.7–20.003
Age 50–75 yrs0.10< 0.001–10.510.1
Age > 75 yrs0.25< 0.001–10.5–10.3
Education level, training–0.050.04–10.100.8
Education level, higher–0.090.001–10.500.7
LifestyleBMI< 18.50.180.00100.8–30.1
BMI 26–300.000.900.600.7
BMI > 300.14< 0.00100.9–10.2
Exercise, weekly–0.10< 0.00120.023< 0.001
RA-relatedDisease duration 3–10 yrs0.020.500.9–10.4
Disease duration > 10 yrs0.17< 0.00100.710.2
Low DAS28 2.60–3.190.19< 0.001–10.2–4< 0.001
Moderate DAS28 3.20–5.100.43< 0.001–3< 0.001–5< 0.001
High DAS28 > 5.100.87< 0.001–5< 0.001–7< 0.001
Extraarticular features (1)0.070.003–20.0500.9
Extraarticular features (≥ 2)0.19< 0.001–20.2–30.06
Joint surgery (1 procedure)0.12< 0.00110.3–20.05
Joint surgery (≥ 2 procedures)0.55< 0.00130.02–40.003
TreatmentMTX monotherapy–0.020.400.801.0
Anti-TNF-α monotherapy0.120.00830.1–40.004
MTX + anti-TNF-α0.060.0610.2–10.3
combination therapy
Glucocorticoid use within0.10< 0.001–20.0100.7
past month
Comorbidity, excluding RAComorbid conditions (1)0.060.03–10.400.6
Comorbid conditions (2)0.14< 0.001–10.4–30.007
Comorbid conditions (≥ 3)0.21< 0.001–30.02–20.03
  • Adjusted R2: HAQ: 0.41, PCS: 0.02, MCS: 0.05. Reference groups: male, age < 50 yrs; education level: elementary; body mass index 18.5–25; exercise: not regularly; disease duration: 0–2 years; DAS28 < 2.6; extra-articular features: none; joint surgery: none; MTX + anti-TNF-α therapy: none; glucocorticoid use: none; comorbid conditions: none.