Patients

In September 1997 a cross sectional sample of 658 patient with AS aged between 16 and 60 years, selected from the Dutch standard diagnosis register of rheumatic diseases (SDR), completed a postal questionnaire on sociodemographics, work status, and disease characteristics including coping. Ninety of these patients were part of a longitudinal study on outcome assessment in AS (OASIS), starting in 1997. Extensive health status assessments of these patients were carried out every six months during the first two years and yearly afterwards. At the fourth year evaluation, the questionnaire on coping was administered for a second time. Details of the patient selection procedures have been published previously^10,11 and can also be found in appendix 1 of the online version of this paper (available at http://www.annrheumdis.com/supplemental).

Questionnaires

In the cross sectional survey, sociodemographic factors comprised sex, age, education, and work status. For further analyses educational level was dichotomised into more than 12 years of formal education and 12 years or less. In the cross sectional as well as in the follow up questionnaire, disease related variables included age at diagnosis, function measured by BASFI (Bath ankylosing spondylitis functional index), and pain measured by BASDAI (Bath ankylosing spondylitis disease activity index). The BASFI comprises 10 questions, each to be rated on a visual analogue scale (VAS; 0–10), on perceived limitations in daily activities.¹² The final score ranges from 0 to 10, and higher values indicate worse physical function. The BASDAI comprises six questions, each to be rated on a VAS (0–10). Five items relate to pain and stiffness in different parts of the body caused by AS, and the remaining item relates to fatigue.¹³ The total score ranges from 0 to 10, and higher values indicate greater disease activity.

Coping was assessed by the CORS, an arthritis specific and patient derived coping questionnaire which measures eight coping strategies directed at the most important chronic stressors of inflammatory rheumatic disease—pain, limitations, and dependency. Three scales refer to pain: comforting cognitions (nine items), decreasing activities (eight items), and diverting attention (eight items). Three scales measure strategies of coping with limitations: optimism (five items), pacing—that is, adapting one’s level of activity (10 items), and creative solution seeking (eight items). Two scales refer to dependency: making effort to accept one’s level of dependence (six items), and showing consideration (seven items). For each item, patients report how often they made use of that particular coping strategy (1 = seldom or never, 2 = sometimes, 3 = often, 4 = very often), and each scale is calculated by summing the scores of the individual items. Higher scores indicate more frequent use of that specific coping style. The two scales, “decreasing activities to cope with pain” and “pacing to cope with limitations”, are classified as the behavioural coping strategies, while all other six coping strategies are considered to be cognitive. The total score for the scale “decreasing activities to cope with pain” ranges from 8 to 32, and for the scale “pacing to cope with limitations, from 10 to 40. Higher values on the scale indicate more frequent use of this coping strategy. The CORS has documented reliability (Cronbach’s α, 0.79 to 0.88; Pearson’s test–retest coefficient, 0.88 and 0.91 for “decreasing activities to cope with pain” and for “pacing to cope with limitations”, respectively), and has been shown to have moderate to low correlation with the sociodemographic variables age, sex, education, and disease duration.⁷ A summary of the domains and scales with sample questions is available in appendix 2 of the online version of this article (http://www.annrheumdis.com/supplemental).

Statistical analyses

Characteristics of the patients were analysed using descriptive statistics. Linear regression was used to analyse the univariate relation (n = 658) between each of the two behavioural coping strategies and the following independent variables: sex, age, disease duration, educational level, physical function, and pain. Variables significantly associated with coping (p<0.05) were included in a multiple linear regression model applying a backward elimination procedure to evaluate the independent contribution of the variables. For all independent variables we give the unstandardised coefficient (B), the standardised coefficient (β), which allows comparison of the relative importance of the variables, and the adjusted correlation (R²), which allows assessment of the contribution of the variable to the explanation of the variability in coping. Agreement between scores of coping at the first assessment (n = 70) and four years later was assessed by intraclass correlation coefficients (ICC). Bland and Altman plots were computed to visualise the difference between coping at the first and second assessment in individual patients.¹⁴ Correlations between change in coping over time and change in physical function (BASFI) or pain (BASDAI) over the same period were analysed by Pearson’s correlation coefficient. Changes in score were calculated as the score at year 4 minus the score at the first assessment. Data were analysed by SPSS version 9.0 (SPSS Inc, Chicago, Illinois, USA).

Patients

In the initial cross sectional group (n = 658), 70% were male, their mean (SD) age was 43.5 (9.4) years, their mean disease duration was 12.3 (8.0) years, 80% had less than 12 years of formal education, and 20% had withdrawn from paid work because of disability. The 70 patients who completed the questionnaire again after four years did not differ in sociodemographic and disease characteristics from the patients in the national group except for a somewhat shorter disease duration (10.5 (7.6) years; p = 0.2). A detailed comparison between the groups is given in appendix 3 of the online version of this article (http://www.annrheumdis.com/supplemental).

Avoidant behavioural coping and health status at the first assessment

In patients from the initial cross sectional group the mean (SD) score for the scale “coping with pain by decreasing activities” was 18.4 (4.3) (interquartile range 15 to 22) and the proportion of patients using this coping strategy often or very often was 42%. The mean score for the scale “coping with limitations by pacing” was 26.4 (6.0) (interquartile range 21 to 30) and the proportion of patients using this coping strategy often or very often was 62%. As can be seen in table 1⇓, worse physical function (BASFI) and more pain (BASDAI) were more strongly related to avoidant behavioural coping strategies than sociodemographic characteristics in univariate analysis. The multivariate analyses (table 2⇓) showed that female sex (B = 1.28 (95% confidence interval (CI), 0.56 to 2.01); p = 0.001) and worse physical function (B = 0.81 (0.61 to 0.99); p<0.001) were associated with the likelihood of decreasing activity to cope with pain (adjusted R² = 0.24), while female sex (B = 1.21 (0.25 to 2.17); p = 0.01), older age (B = 0.12 (0.07 to 0.17); p<0.0001), and worse physical function (B = 0.99 (0.81 to 1.18); p<0.0001) were associated with likelihood of pacing to cope with limitations (adjusted R² = 0.22). In the multivariate analyses, the BASDAI made no independent contribution to coping, probably because of the strong correlation between BASDAI and BASFI (R² = 0.70; p = 0.01), as can be seen online in appendix 4 (http://www.annrheumdis.com/supplemental).

Avoidant behavioural coping and change over time

In the overall group, disease duration showed no association with coping at the first assessment in the multivariate analyses. In the 70 patients taking part in the longitudinal study, the mean (SD) score for decreasing activities to cope with pain at the first assessment was 18.4 (4.4) and at year 4, 19.2 (4.0). Pacing to cope with limitations at the first assessment was 25.9 (6.4) and at year 4, 27.9 (5.4). The mean (SD) difference in score for decreasing activities to cope with pain was 0.77 (4.6) (range −9 to 13), and for pacing to cope with limitations, 0.76 (5.6) (range −8 to 20).

Although the mean group values suggested small differences in coping over time, the ICCs suggested only moderate agreement. The ICC of the coping strategy “decreasing activities to cope with pain” at the first assessment and after four years was 0.56 (0.34 to 0.74). The ICC of the coping strategy “pacing to cope with limitations” at baseline and four years later was 0.70 (0.53 to 0.82). The Bland and Altman plots can be seen in fig 1A and 1B⇓⇓. Each dot represents one patient, with the mean coping of the two assessments on the X axis and difference in coping between the year 4 assessment and the first assessment on the Y axis. If there were no individual change in coping between the two assessments, all dots would be on the zero line of the Y axis (difference between coping at year 4 and at the first assessment). The plots in fig 1⇓ suggest a difference in coping over time, with changes in coping strategies in both directions—some patients using the strategy more often and others less often. The change in coping over time could not be explained by the change in physical function or pain, as can be seen from the very low Pearson correlation coefficients of the change values of coping and health status (decreasing activities and BASFI, 0.03 (p = 0.8); decreasing activities and BASDAI, 0.09 (p = 0.4); pacing and BASFI, 0.07 (p = 0.6); pacing and BASDAI, 0.09 (p = 0.5). The absence of a relation between change in coping over time and change in health status (BASFI or BASDAI) could not be explained by ceiling or bottom effects in the coping strategy. Both coping strategies were normally distributed (skewness for coping with pain, −0.1, and for coping with limitations, −0.3), and few patients had a minimum or a maximum score (two patients had a minimum score: one for coping with pain, the other for coping with limitations; one patient had a maximum score, for coping with limitations).

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Figure 1

 Bland and Altman plots to illustrate difference in each of the two behavioural coping strategies (decreasing activity to cope with pain (A) and pacing to cope with limitations (B)) at the first assessment (year 0) and year 4 (n = 70). The dotted lines present the standard deviation of the change value.

Conclusions

There is evidence that behavioural coping strategies are not completely stable over time, but this change seems independent of disease duration and disease related change in physical function and pain. As behavioural coping is associated with functional outcome, it would be of value to gain improved insight into the variables that influence coping and which might be modifiable.