Results

At presentation, there was little variation across the deprivation groups in age, sex, duration of symptoms, the proportion of patients positive for RF, or in the proportion with bony erosions (table 1). There was, however, strong evidence of a positive deprivation trend with HAQ score and joint score, and weaker evidence of a negative trend with grip strength. ESR and pain scores were fairly constant across deprivation groups, and the trends were statistically non-significant at the 5% level. In England and Wales the proportions of enumeration districts in these quartiles are 20.4% (least deprived quartile, Q1), 17.7%, 19.8%, and 42.0%. Thus the ERAS study group was somewhat less deprived than the national average.

The mode of treatment was fairly consistent across the deprivation groups (table 2), including use of low dose steroids alone (8–10%). The unadjusted analysis provided evidence of a trend of more complex drug treatment (that is, second line drug combinations after loss of effect of the first or second disease modifying drug) in patients from more deprived areas, but the significance was lost (p=0.18) after adjustment for age, sex, and treatment centre. The trend of more inpatient medical treatment in patients from more deprived enumeration districts was also lost after similar adjustment (p>0.2).

By three years, each of the main clinical markers (HAQ, ESR, joint score, pain score, grip strength) had improved (changes in HAQ shown in fig 2), though the socioeconomic differentials seen at presentation remained or were accentuated: statistically significant positive trends were seen between deprivation and functional grade, HAQ, and joint scores, and a negative association was seen with grip strength. As before, x ray erosions, ESR, and pain score showed no statistically significant association (trends non-significant at the 5% level). The change between presentation and three years in HAQ score, ESR, joint and pain scores, and grip strength did not vary appreciably with deprivation, and in no case was the pattern or statistical test strongly suggestive of a trend.

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Figure 2

Change in mean Health Assessment Questionnaire (HAQ) score (log scale) by quartile (Q1 least deprived, Q4 most deprived) of the Carstairs deprivation score.

Table 3 shows the results of the multivariable analyses. The probability of having an HAQ score above the median at three years was greater in women than men and greater in those aged 45 years or more compared with younger patients. The probability was also substantially greater in those with high HAQ scores at presentation. After adjusting for these factors and for the treating hospital, an increase from the 5th to the 95th centile of the deprivation distribution was associated with an odds ratio of 1.74 (95% CI 1.10 to 2.74). Thus patients from more deprived enumeration districts were at greater risk of a high HAQ score at three years after allowing for their higher initial scores—that is, they showed less improvement over time.

Discussion

There is no evidence that the development of RA is affected by socioeconomic status,7 but it is clear from our results that the effect of deprivation is apparent at first presentation, and that older women from a lower socioeconomic environment and with an initially worse HAQ did not follow the overall trend for improvement in function.

Functional ability is considered an important measure of clinical status of RA and outcome, and the HAQ a valuable and widely used tool for this.16 The HAQ has been reported to be the most representative of all variables in depicting clinical status in RA,21 and is the health status measure most commonly used by rheumatologists in the UK at present.22 In a recent review of prognostic factors in RA the HAQ has been shown to have predictive qualities for morbidity, mortality, and functional outcome in a number of reports.23 This makes the findings of this study relevant to clinicians and patients for management and prognosis. The HAQ is a measure of patients' perspective of disease and reflects the true needs of patient care. It does not have a psychological component and any possible effect of anxiety or depression on function cannot be included in our analysis. None the less, it is important to detect early loss of function so that coping measures can be introduced without delay and support provided by physiotherapy and occupational therapy departments, and disease modifying drugs given early consideration.24 ,25 Older women of lower socioeconomic status with worse HAQ at presentation could be identified early on.

Evidence from this study suggests that socioeconomic differentials in disease status at presentation were apparent in other more objective markers of joint disease (for example, swollen joints). Possible explanations are that patients from more deprived enumeration districts had higher thresholds for consultation or that they were more prone to the effects of rheumatoid disease. There was, however, no evidence of longer duration of symptoms before attending hospital in these patients, though the measure of disease duration depended on patient recall and may be imprecise. It is not possible from our study to know whether patients with milder onset RA in deprived areas are less likely to seek medical advice, whereas patients from privileged environments more likely to do so, and whether perceptions of disease onset and severity vary according to educational background.

Whether measured by income, occupation, educational level, or social class, poor socioeconomic environments have been shown to affect outcome adversely in many chronic disorders and have important implications for healthcare strategies.26 The conclusion of a summary of the current position in the UK was that most inequalities in health are not inevitable and are remedial.27 Educational status was first described as an important predictor of outcome in RA in cross sectional studies from the US,1 ,8 and confirmed in two small prospective studies in Europe.28 ,29 The strength and significance of this association vary, probably because of differences in ascertainment of the different educational systems in these countries. In view of the effect of age on educational attainment in the UK, enumeration district based on postal code may be a more reliable index of socioeconomic status, and a study using this method in patients with RA entered into clinical trials in western Scotland found similar results.3 This group have also reported a link between premature mortality and social deprivation.30 We found little evidence of this, but over the three year follow up only 37 deaths occurred. Secure conclusions about a deprivation link will be possible from our cohort only after further follow up.

The wide variation in the severity of functional outcome in studies of RA progression is, at least in part, due to study design (especially patient selection) and limited numbers.23 The design of ERAS was intended to overcome some of these problems, and has recruited patients from various socioeconomic and geographical areas. In the first few years of RA clinical, functional, and laboratory measures improved overall. There are few reliable and consistent clinical or laboratory features which predict those who do badly in this time, but female sex, acute phase (ESR, C reactive protein) and RF have all been shown to predict a variety of outcomes. However, these features do not always hold for function, and there has been much less consistency in predicting functional outcome than radiological damage.23The most reliable measure at the early stages of RA for predicting eventual functional outcome is functional ability at presentation,23 but the clinical use of this finding has been little explored. The evidence from our study suggests that disease progression over the first three years from presentation was worse in patients of greater socioeconomic deprivation, even after allowing for their poorer initial HAQ scores. Thus not only did they present with more severe disease as measured by the HAQ but they also did not improve as much as patients of equivalent initial HAQ scores from areas of less socioeconomic deprivation. Women and older patients also fared badly. There was some evidence of differences in treatments received (antirheumatic drugs and inpatient interventions) by socioeconomic status, but this was largely attributable to differing practices at the nine contributing centres in this study; and adjustment for centre removed evidence of an association. Although predictive factors have a number of uses, the most important one for clinicians is as a guide to treatment and early management strategies. Socioeconomic factors may have a place in the currently rather limited number of reliable prognostic factors in early RA.

Potential sources of bias in this study arise from selective referral and losses to follow up. There were neither appreciable differences in clinical or laboratory variables at presentation between those who attended at three years and those who were lost to follow up, nor any clear socioeconomic trends, except in those patients who died, and in this group, the higher proportion of older and male patients with worse function was not surprising. The nature of selection of our patients and the smaller percentage of patients who were lost to follow up favour less bias or cohort effects. The observed/expected ratio for survival was similar to a comparable study,31 and exclusion from the main analysis of the patients who died would, if anything, underestimate the extent of deprivation on disease severity.

A few studies have reported a link between socioeconomic status and severity of RA,1-3 and while the development of RA may itself contribute to worse socioeconomic status, our study is the first to show that this effect is already apparent at presentation (at a median of six months from onset of symptoms). Further research is required to establish the relevance of other factors which contribute to greater deprivation—for example comorbidity, diet, smoking, and which of these factors can be most easily improved. In recent years greater emphasis has been towards psychosocial explanations of socioeconomic inequalities and the concept of low perceived control.32 ,33 The early HAQ changes found in our study raise the possibility of a positive discrimination programme for patients disadvantaged in this way. At present there is no provision for allocating funding in rheumatology nationally for those most in need, but at least rheumatologists and primary care doctors need to be aware of the factors likely to be associated with poor functioning at the early stages of RA, when intervention is most likely to benefit the patient. This study suggests that age, sex, HAQ, and the Carstairs deprivation score are useful for risk stratification, helping to identify patients with RA who may need more intensive drug treatment and other interventions at an early stage.