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Clinical and epidemiological research
Extended report
Decline in work disability caused by early rheumatoid arthritis: results from a nationwide Finnish register, 2000–8
  1. Vappu Marianna Rantalaiho1,
  2. Hannu Kautiainen2,
  3. Salme Järvenpää3,
  4. Lauri Virta4,
  5. Timo Pohjolainen5,
  6. Markku Korpela1,
  7. Timo Möttönen6,
  8. Kari Puolakka7
  1. 1Department of Internal Medicine, Centre for Rheumatic Diseases, Tampere University Hospital, Tampere, Finland
  2. 2Unit of Primary Health Care, Kuopio University Hospital, Kuopio, Finland
  3. 3Medcare Foundation, Äänekoski, Finland
  4. 4Social Insurance Institution, Turku, Finland
  5. 5Rehabilitation Unit, Orton Hospital, Helsinki, Finland
  6. 6Department of Rheumatology, Turku University Central Hospital, Turku, Finland
  7. 7Department of Medicine, Lappeenranta Central Hospital, Lappeenranta, Finland
  1. Correspondence toVappu Marianna Rantalaiho, Tampere University Hospital, PO BOX 2000, FI-33521 Tampere, Finland; vappu.rantalaiho{at}pshp.fi

Abstract

Objectives To study whether the work disability (WD) rates in early rheumatoid arthritis (RA) have changed in Finland, where the treatment of RA has long been active but has intensified further since 2000.

Methods All incident non-retired patients with RA of working age (18–64 years) in a nationwide register maintained by the Finnish Social Insurance Institution from 1 January 2000 to 31 December 2007 were identified. Patient cohorts were analysed in 2-year time periods (2000–1, 2002–3, 2004–5, 2006–7) and initial disease-modifying antirheumatic drugs (DMARDs) were elucidated from the drug purchase register. The incidence of continuous WD in the RA cohorts as well as in the entire Finnish population up to 31 December 2008 was analysed.

Results A total of 7831 patients were identified (71% women, 61% rheumatoid factor-positive). Throughout the follow-up period the use of methotrexate and combination DMARDs as the initial treatment of early RA increased. During the first 2 years the incidence of RA-related continuous WD was 8.9%, 9.4%, 7.2% and 4.8% in the year cohorts, respectively (p<0.001 for linearity). Compared with the entire Finnish population, the age- and sex-stratified standardised incidence ratio of a WD pension due to any cause was 3.69, 3.34, 2.77 and 2.80 in the year cohorts, respectively (p<0.001 for linearity).

Conclusions Since 2000 the frequency of continuous WD in early RA has declined in Finland. The present data allow no explanatory analysis but, at the same time, increasingly active treatment strategies have been introduced.

https://doi.org/10.1136/annrheumdis-2011-200701

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    Introduction

    In clinical studies, actively treated patients with rheumatoid arthritis (RA) have lower disease activity, more frequent remissions and less radiographic progression than conservatively treated patients.1,–,5 These findings have led to specific treatment recommendations and clinical practice appears to have changed accordingly.6 ,7

    Work disability (WD) is one of the devastating outcomes of RA. Depending on study populations and on national differences in social security systems, 20–40% of previously employed patients with RA become permanently work disabled within 2 years after diagnosis and 40–80% during the 5–20 years after diagnosis.8 Some studies have shown that early remissions predict better maintenance of working capacity,9 but how these study results translate into real life is not evident. Biological agents have shown promising results on clinical outcomes and their use has significantly increased during this millennium, but their effect on the maintenance of working capacity of patients with RA is ambiguous.10,–,14

    Furthermore, there is a great national variation between the rates of permanent WD; in some countries patients with RA with low disease activity become work disabled while, in others, patients with severe disease activity continue working.15 ,16 The most reliable research method for trends in WD is therefore to study them longitudinally in the same setting.

    We have previously shown that in Finland the treatment of early RA has been active and has recently further intensified.7 In this study we attempted to elucidate whether this modern era has brought any changes in the trends in RA-related WD in Finland.

    Methods

    Finland has a general sickness insurance covering the entire population, and all permanent residents are issued a personal health insurance. The Social Insurance Institution (SII) grants patients with chronic inflammatory rheumatic disorders a special reimbursement of 72% for antirheumatic drugs, and practically every Finnish patient with antirheumatic medications receives it. All medicine reimbursement decisions are gathered in a nationwide register maintained by the SII. Furthermore, the SII maintains a prescription register of the drugs purchased from pharmacies and reimbursed according to a special rate.7

    If Finnish residents aged 16–67 years become unable to perform their regular or corresponding jobs, they are entitled to a sickness allowance as a compensation for lost income. All 16–64-year-old people who have lived in Finland for at least 3 years and who have an illness, injury or defect that prevents them from earning a reasonable living (stated by a doctor's certificate) can, after 150 working days of WD, and must, after 300 days of WD, apply either for a temporary rehabilitation allowance or a permanent disability pension. Permanent disability pensions are usually antedated by rehabilitation allowances of varying durations and granted, at the earliest, after 1 year's WD, for persons aged >60 years on somewhat easier terms. The SII and the Finnish Centre for Pensions maintain a register on sick leaves, rehabilitation allowances and permanent disability pensions.

    Patient cohort

    From the nationwide register maintained by the SII we collected data on patients aged 18–64 years who were available for work when they, for the first time in their life, had been granted a special reimbursement of medications for rheumatoid factor (RF)-positive (ICD-10 diagnosis M05) or RF-negative RA (M06) from 1 January 2000 to 31 December 2007. The data included sex, birth date and the date of the reimbursement decision (index day, equalling RA diagnosis). No other clinical data were available. The patient data were analysed in 2-year cohorts (2000–1, 2002–3, 2004–5, 2006–7) according to the index day.

    For these cohorts we collected from the registers of the SII and of the Finnish Centre for Pensions data on annual WD days in 365-day cycles from the index date, including all periods of sickness allowance, temporary rehabilitation allowance, partial disability pensions (number of days divided by two) and of permanent disability pension from 1 year before the index day up to the end of the follow-up period (31 December 2008). However, sick leave lasting ≤10 days could not be assessed as this is not compensated by the SII. The annual WD days per patient years for any reason were counted. Patients already on partial pensions on the index date were also included in the analysis.

    During the same period the incidence of continuous WD was assessed by elucidating all permanent disability pensions and long-term rehabilitation allowances still continuing at the end of the follow-up period, including continuous WD for any reason and that exclusively due to RA. Follow-up of patients ended when they retired for reasons other than RA, reached 65 years of age or died, whichever occurred first. From the same institutes we also obtained the incidence data for WD pensions of all Finnish citizens aged 18–64 years.

    We also obtained data from the reimbursement drug register on the drugs purchased by these patient cohorts from 31 days before the index day to 91 days after the index day and investigated the early drug treatment strategies: no disease-modifying antirheumatic drugs (DMARDs), any single DMARD, single methotrexate (MTX), any combination of DMARDs or a combination of DMARDs including MTX. The commencement of adalimumab or etanercept any time during the follow-up period was also noted. Intravenous drugs are given and paid for by hospitals and outpatient clinics and are not registered by the SII so our study does not include infliximab or other infusion-based biological therapies.

    Statistical methods

    The results are expressed as means with SD and as medians with IQR. Statistical significance for hypotheses of linearity was evaluated by analysis of variance or the Cochran–Armitage test. The incidence of RA for each 2-year cohort with 95% CIs was calculated assuming a Poisson distribution using the 18–64-year-old Finnish population (from Statistics Finland) as reference. The 95% CIs for annual WD days were obtained by bias-corrected bootstrapping and the linearity across year cohorts was tested by bootstrap-type analysis of covariance with an appropriate contrast. The cumulative incidence of continuous WD was estimated and illustrated by the Kaplan–Meier method. In order to adjust for confounding factors, differences between the groups and the hypothesis of linearity were tested by using Cox regression models with a contrast when appropriate. The Cox multivariate regression model was also used to analyse factors associated with continuous WD. The patients with RA and the population at risk were stratified by gender, age (in 5-year categories) and calendar years, and incidence rates with 95% CIs were calculated. The ratio between observed and expected numbers (standardised incidence ratio) was calculated with 95% CIs assuming a Poisson distribution. The significance of the hypotheses of linearity was evaluated by Poisson regression models.

    Results

    We identified a total of 7831 patients with RA (71% women, 61% RF-positive) of working age (18–64 years) who, at the index date, were available to work full-time. Further, a cohort of 137 patients who were already part-time retired at the index date were included in the analysis of mean annual WD days. The demographic data are presented in table 1. During the follow-up the use of single DMARD treatment during the first 3 months decreased while that of combination DMARDs increased. The use of MTX either alone or in combination increased. The administration of adalimumab or etanercept for patients occurred rarely.

    View this table:
    Table 1

    Demographic data and initial treatment strategies of the 7831 patients with a recent diagnosis of RA available to work at baseline

    One year preceding the index date the median (IQR) duration of WD periods of >10 days was 0 (0–4) days per year in all cohorts. During the first year after the index date the mean number of annual WD days per patient years was similar in all year cohorts (45–50 days per year), decreasing during the second year and increasing steadily thereafter (figure 1). The mean number of annual WD days per patient years during the second year decreased along the year cohorts (p=0.002 for linearity adjusted for age, sex and RF). When the data of all cohorts during the first 2 years were analysed together, the mean number of annual WD days per patient years was 53 in men and 37 in women (mean ratio between men and women 1.42 (95% CI 1.28 to 1.54)), while 45.6% (95% CI 43.6% to 47.6%) of the men and 48.2% (95% CI 46.9% to 49.5%) of the women had no registered WD days during the first 2 years after the RA diagnosis.

    Figure 1
    Figure 1

    Mean annual work disability days due to any cause per patient years in the cohorts of patients with early rheumatoid arthritis. Age- and sex-adjusted p values show the statistical significance between the groups at years 1 and 2, during which all groups are followed up.

    The median (IQR) follow-up time was 4.0 (2.2–6.3) years. By 8 years, 14.5% (95% CI 13.5% to 15.5%) of patients of the total patient population had retired due to RA. In women the cumulative incidence of RA-dependent continuous WD was 12.6% (95% CI 11.5% to 13.7%) and in men it was 19.2% (95% CI 17.1% to 21.4%) (age- and RF-adjusted HR 0.68 (95% CI 0.59 to 0.78), p<0.001, figure 2).

    Figure 2
    Figure 2

    Kaplan–Meier curves with CIs of the incidence of (A) rheumatoid arthritis (RA)-related continuous work disability (WD) and (B) all-cause continuous WD in men and women after the diagnosis of RA. The numbers of men and women with RA at risk at 0, 2, 4, 6 and 8 years on whom the estimates are based and, in parentheses, the numbers of events during the preceding period are shown below the x-axis.

    During the first 2 years after the diagnosis the incidence of RA-related continuous WD was 8.9% (95% CI 7.7% to 10.3%), 9.4% (95% CI 8.2% to 10.8%), 7.2% (95% CI 6.2% to 8.5%) and 4.8% (95% CI 3.9% to 5.9%) in the year cohorts 2000–1, 2002–3, 2004–5 and 2006–7, respectively (age-, sex- and RF-adjusted p<0.001 for linearity). Figure 3 presents the Kaplan–Meier curves for continuous WD in different year cohorts during the 8-year follow-up period.

    Figure 3
    Figure 3

    Kaplan–Meier curves of the incidence of continuous work disability (WD) due to rheumatoid arthritis (RA) in different patient cohorts with early RA. The broken line shows the estimated cumulative incidence of WD pension due to any cause in the general population.

    In a Cox multivariate analysis for the total follow-up time, the year cohort, age and sex were related to continuous WD (table 2). In the same model, when single non-MTX DMARDS as an initial treatment was used as a reference, all other active treatment strategies (but not no-DMARDs) significantly increased the risk of continuous WD. However, adalimumab and etanercept appeared to protect the patients from continuous WD (table 2). Nevertheless, their use was rare. During the follow-up period these tumour necrosis factor (TNF) inhibitors were prescribed to 277 patients (70% women, mean (SD) age on index day 41 (12) years; table 1) and were started a mean (SD) 2.6 (1.8) years after the index day.

    View this table:
    Table 2

    Cox multivariate regression analysis of factors predicting continuous RA-related WD in patients with a recent diagnosis of RA

    In the whole Finnish population of working age the incidence of preterm WD pension for any reason remained stable (0.7% in 2000 and 0.8% in 2008). Compared with the Finnish population, the age- and sex-stratified incidence ratio for a WD pension in our early RA population was 3.16 (95% CI 2.97 to 3.35) and declined along the year cohorts (figure 4).

    Figure 4
    Figure 4

    Standardised incidence ratio for a premature disability pension due to any cause in Finnish patients with early rheumatoid arthritis compared with the general Finnish population. The Finnish legislation was reformed in 2004, prioritising vocational rehabilitation over work disability pensions.

    Discussion

    This study shows that in Finland the frequency of continuous WD in early RA is declining while the incidence of all disability pensions in the Finnish population has remained stable. This favourable development has occurred in parallel with increasingly active treatment strategies used for early RA, even though we failed to confirm a direct protective relationship between traditional DMARD treatments and WD.

    During the first year after the diagnosis of RA the majority of WD days are due to temporary sick leaves and thereafter they are mainly due to permanent disability pensions, as shown by the FIN-RACo study.17 The rates of permanent WD in earlier cohorts of patients with RA have been around 20% after 2 years and 50% after 5 years of RA.8 In European studies in particular, the WD has occurred quite early after the diagnosis of RA18 ,19 whereas, in the USA, presumably due to differences in the sickness benefit systems, permanent WD has increased only later in the disease course.20 Compared with earlier European and Scandinavian reports (including those from Finland),21,–,25 the new Finnish WD rates in early RA clearly appear to be lower and their incidence is decreasing further. A recent large Swedish study found a similar trend of decreasing number of annual WD days in the latest early RA cohort compared with earlier cohorts.26 However, the mean number of annual WD days in these Swedish cohorts was 2–4 times higher than in the current Finnish cohorts and the proportion of patients not using sick leave was lower than in our cohorts.

    There are some possible explanations for the declining trend in RA-dependent WD. First, legislative changes could affect the permanent WD pension rates and, indeed, in Finland the legislation was reformed in 2004, prioritising vocational rehabilitation over a WD pension and transferring the responsibility of organising it to the pension providers. While it is possible that this has affected the WD pension rates in patients with RA, the rate of WD pensions in the general population remained at a similar level throughout the follow-up period.

    Earlier data comparing the incidence of permanent WD between patients with early RA and the general population are sparse. Two studies from the Netherlands found a 4–7-fold risk for WD in early RA compared with the general population19 ,27 and a UK study reported a 32-fold risk.28 Compared with these, the threefold risk caused by early RA found in this study is significantly lower but still presents a considerable problem, giving an informative estimate for patients and for the authorities of the current threat caused by RA to patients' working ability.

    The second possible explanation for the decline in continuous WD in early RA is the contemporary change in treatment strategies aimed at early diagnosis and treatment, targeting remission or low disease activity. We also found a shift towards more active treatment strategies in early RA during our follow-up period.7 However, undoubtedly due to a channelling bias, patients receiving the mildest initial treatment (ie, single non-MTX DMARD) had a lower risk of WD than those initially treated more actively. Nevertheless, it is evident that, in the continuum of clinical disease activity in early RA, patients with mild RA and therefore the best prognosis at disease onset are the ones prescribed the mildest treatments while patients receiving more aggressive treatments are the ones with active disease and therefore an unfavourable consequent working ability. If any of these patients had been treated with less effective strategies their WD rates would probably be much higher.

    Regardless of the channelling bias discussed above, TNF inhibitors (adalimumab and etanercept) protected the patients' working ability. Nevertheless, their use was uncommon and they were first started a few years after the diagnosis, so the use of biological agents can explain only a very small part of the total decline in RA disability pensions. Unfortunately our data on biological agents is limited as we have no data on hospital-based medications such as infliximab which are not reimbursed by the SII but funded by hospitals. Infliximab was the first TNF inhibitor to become available in Finland in 1999, followed by etanercept in 2002 and adalimumab in 2003, and the other biological agents became available only after the end of our study period. After their introduction the SII-reimbursed etanercept and adalimumab often displaced infliximab as the first biological agent for financial reasons. All of the biological agents were first reserved for patients with treatment-resistant and therefore often longstanding RA and their use in early RA was exceptional.29 More evidence is therefore needed about the role of early treatment with biological agents in maintaining working ability.

    The third potential explanation for the decline in disability pensions is the change in attitude by both patients and physicians towards the prognosis of RA. With better outcomes from treatment of RA, permanent inability to work has ceased to be a self-evident consequence. Furthermore, the authorities who give their expert opinion on whether a patient qualifies for a disability pension may have adopted a similar change in attitude.

    The main strength of our study is that it is unbiased, including all Finnish patients with early RA and not a population that is in any way selected. Moreover, we have highly reliable and extensive register data on WD as well as on RA medications and, furthermore, the comparison with the general population is reliable as all Finnish citizens available to work are included in the control material.

    One limitation of our register-based study is the patient inclusion on the grounds of a drug reimbursement decision, which however, practically all Finnish patients with RA receive.7 Furthermore, the incidence of RA in the present population30 is not lower than in earlier reports from Finland31 or from other countries,32 indicating comprehensive patient inclusion.

    Other limitations of our study are that we have no data on short periods of sick leave (<10 days) since these are not registered by the SII, making our results an underestimate. A further important limitation is the lack of clinical and radiographic data and of details of employment and education of the patients which means we are unable to analyse the patient-dependent factors behind the observed trend in WD pensions. However, there is ample evidence to show that the main patient-dependent factors predicting WD are severe and longstanding RA, reduced functional ability, physically demanding work and higher age.8 Of these, we confirmed that higher age is a significant risk factor for premature WD in early RA. Interestingly, we also found that men had a higher risk of RA-related WD than women. One earlier study showed a slightly increased risk for arthritis-related WD in men,33 while some have found an increased risk in women16 ,26 ,34 and others found no association with gender.18 ,19 ,35 ,36 Different risk factors predispose men and women to WD.37 Nonetheless, comparing our results with those of others is difficult as we lack the clinical and socioeconomic data and because some studies include patients with self-reported arthritis of any type.33 ,34 Also, defining WD according to the patient's self-report of not being employed might produce uncertain results,35 especially in countries where women are not such an active component of the workforce as in Finland where participation in the workforce is similar in men and women of working age (70% and 71%, respectively, in 2008 according to Statistics Finland). Thus, a higher rate of engagement in housekeeping and lesser paid employment does not explain the lower risk for WD in women. Nevertheless, the fact that men are more likely to do manual labour than women could partially explain our finding.

    In conclusion, our results show that it is possible to decrease or to postpone long-term WD in patients with early RA. This development has occurred in parallel with increasingly active treatments with conventional DMARDs, possibly altered attitudes towards the prognosis of RA and legislative changes emphasising vocational rehabilitation. The use of TNF inhibitors has contributed to preserving the patients' working ability, but their use explains only a small part of this favourable outcome, at least in Finland.

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    Footnotes

    • Ethics approval There was no legal requirement for approval by an ethics committee since only unidentifiable register data were used and the patients were not contacted.

    • Funding This study was financially supported by the Competitive Research Funding of the Tampere University Hospital (Grant 9M124).

    • Competing interests None.

    • Provenance and peer review Not commissioned; externally peer reviewed.