Background/Purpose: Rheumatoid arthritis (RA) is generally described as a disease with two peaks of onset, either late (late onset RA, LORA) or early (young onset RA, normal 30-55 years, YORA). Considering that the average age of the population is continuously rising, LORA will gain importance in the near future. Despite this growing importance LORA has not been the focus of much interest in the past. This study was set up to analyse disease activity and progression in LORA in comparison to YORA patients with early disease.

Methods: This is a cohort study within the Swiss RA registry SCQM. We included all patients with recent onset arthritis, either RA (disease duration ≤1 year) or undifferentiated, as diagnosed by the data-entering physician. Patients were followed up to 5 years. The cut off between YORA and LORA was operationally set at 60 years of age. Disease progression and activity was assessed based on DAS 28 and the progression of joint erosions using the Ratingen score.

Results: A total of 592 patients with early undifferentiated or RA was analysed. The age at disease onset had a Gaussian distribution, with a single peak at 60 years of age. 366 patients were 60 years or younger (YORA) and 226 patients were older (LORA) at disease onset. DAS 28 scores were significantly higher among LORA as compared to YORA patients (4.8 vs. 4.5, p = 0.049). Corticosteroids were used in 68% of LORA patients as a first line treatment, compared to 25.4% in YORA patients (X² test, p < 0.0001). DMARDs, on the other hand, were used in 100% of the YORA patients as first line treatment compared to 91.2% of the LORA patients. During follow up, new glucocorticoid, synthetic, or biologic DMARD were initiated in 32.8%/61.1%/14.1% of all decisions documented among YORA patients and 17.5%/54.6%/6.6% in LORA patients (X² test, all p < 0.0001. The DAS28 scores decreased in both groups over the observed time period, and the initial differences in disease activity vanished after 1/2 year and during the subsequent follow up. The Ratingen score was higher in LORA than in YORA patients at inclusion (12.7 vs. 5.6, p < 0.0001). The rate of radiological progression at 5 years was similar comparing LORA and YORA (3.3 vs. 2.6, resp., p=0.64). The level of Ratingen scores at onset and during follow up over 5 years did not clearly separate LORA and YORA into two groups), but rather increased linearly when comparing the patients in groups per decade from 20 to 92 years of age.

Conclusion: Our results do not support the existence of a separate LORA subgroup with a distinct peak of incidence and/or course of the disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-late-onset-rheumatoid-arthritis-lora-really-a-distinct-entity-of-ra-results-from-the-swiss-observational-cohort/