Trajectories of functional limitation in early rheumatoid arthritis and their association with mortality

Objective: This study aimed to identify subgroups with distinct trajectories of functional (HAQ) progression over 10 years following diagnosis of RA and identify baseline characteristics associated with the trajectories and their prognostic value for mortality.

Methods: Between 1986 and 1998, 1460 patients with RA symptoms <2 years and prior to disease-modifying treatment (DMARDs) were recruited to an inception cohort (Early RA Study). Standard clinical, functional and laboratory assessments were performed at presentation and annually. Deaths were tracked by the National Health Service Central Register. Growth mixture modelling was used to identify distinct trajectories of HAQ score progression and survival analysis employed to compare all-cause mortality across the trajectory classes.

Results: Four HAQ score progression classes were identified: moderate increasing (46%), low stable (6%), moderate stable (28%) and high stable (20%). Only the moderate-increasing class exhibited an accelerated decline in function over normal ageing. Compared with the moderate-increasing class, individuals with high-stable HAQ scores were more likely to be female, have more severe disease and other coexistent conditions. Low-stable class patients were more likely to be male and report less pain. The high-stable class had increased risk of mortality compared with the moderate-increasing class after adjusting for potential confounding factors, whereas low-stable and moderate-stable classes were at reduced mortality risk.

Conclusion: The effect of RA on function is set within the first few years and is affected by comorbidity. Identifying distinct groups of patients may help to target those at greater risk of poor functional outcome and mortality.