Longitudinal regression of clinical parameters on depressed mood, daily stressors, avoidance coping and social support
| Independent variables | VAS pain | VAS morning stiffness | Tender Joint Count 53 | Erythrocyte Sedimentation Rate | |||||||||
| B | 95% CI | Obs | B | 95% CI | Obs | RR | 95% CI | Obs | Exp(B) | 95% CI | Obs | ||
| 1 | Depressed mood (HADS depression score) | 2.34 | 1.59 to 3.08 | 886 | 4.09 | 1.18 to 7.00 | 892 | 1.06 | 1.03 to 1.09 | 894 | 1.01 | 0.99 to 1.03 | 821 |
| Between-subject effect | 2.63 | 1.76 to 3.50 | 4.62 | 1.34 to 7.89 | 1.08 | 1.04 to 1.12 | 1.03 | 1.00 to 1.06 | |||||
| Within-subject effect | 1.55 | 0.11 to 2.98 | 2.14 | −4.14 to 8.41 | 1.02 | 0.97 to 1.08 | 1.00 | 0.98 to 1.02 | |||||
| 2 | Daily stressors (EPCL frequency score) | 0.44 | 0.04 to 0.84 | 892 | 0.31 | −1.19 to 1.80 | 898 | 1.01 | 0.99 to 1.02 | 900 | 1.00 | 0.99 to 1.01 | 827 |
| Between-subject effect | 0.59 | 0.11 to 1.07 | −0.15 | −1.89 to 1.58 | 1.01 | 0.99 to 1.03 | 1.01 | 0.99 to 1.02 | |||||
| Within-subject effect | 0.12 | −0.59 to 0.83 | 1.67 | −1.32 to 4.66 | 0.99 | 0.97 to 1.02 | 1.00 | 0.98 to 1.01 | |||||
| 3 | Avoidance coping (UCL avoidance score) | 0.47 | −0.49 to 1.42 | 883 | −0.66 | −4.22 to 2.89 | 889 | 1.03 | 1.00 to 1.07 | 891 | 0.99 | 0.97 to 1.01 | 818 |
| Between-subject effect | 1.03 | −0.15 to 2.21 | −0.22 | −4.38 to 3.94 | 1.01 | 0.97 to 1.07 | 1.02 | 0.98 to 1.06 | |||||
| Within-subject effect | −0.58 | −2.19 to 1.02 | −1.87 | −8.74 to 4.99 | 1.05 | 0.99 to 1.12 | 0.98 | 0.96 to 1.01 | |||||
| 4 | Social support (IRGL perceived support) | −1.97 | −2.77 to –1.17 | 892 | −4.34 | −7.40 to –1.28 | 898 | 0.93 | 0.91 to 0.96 | 900 | 1.00 | 0.98 to 1.02 | 826 |
| Between-subject effect | −2.24 | −3.23 to –1.25 | −3.65 | −7.26 to –0.05 | 0.93 | 0.89 to 0.97 | 1.00 | 0.96 to 1.03 | |||||
| Within-subject effect | −1.47 | −2.82 to –0.12 | −6.11 | −11.93 to –0.30 | 0.94 | 0.90 to 0.99 | 1.00 | 0.98 to 1.02 | |||||
B, regression coefficient; analysed with linear mixed models analyses taking into account left censoring. RR, rate ratio; analysed with negative binomial mixed models taking into account left censoring in a variable in which a score of 0 really means zero. Exp(B), exponent (regression coefficient); analysed with linear mixed models in which ESR was log-transformed (ln(ESR)) because of skewness to the right.
Hybrid mixed models were used to split the Bs and RRs into a between-subject (ie, cross-sectional) and within-subject (ie, longitudinal) effect. The between-subject effect shows the difference in the outcome variable between two patients having a one-unit difference in the independent variable. The within-subject effect shows the increase in the outcome variable within one patient when the independent variable increases with one unit.
In bold are statistically significant associations with a p value <0.05.
EPCL, Everyday Problem Checklist; ESR, erythrocyte sedimentation rate; HADS, Hospital Anxiety and Depression Scale; IRGL, Impact of Rheumatic Diseases on General Health and Lifestyle; Obs, number of observations of the outcome used in analysis; UCL, Utrecht Coping List; VAS, Visual Analogue Scale.