Influence of age and sex on functional outcome over time in a cohort of patients with recent-onset inflammatory polyarthritis: Results from the Norfolk arthritis register

Objective It has been found that women with rheumatoid arthritis (RA) have a poorer prognosis than men. However, the impact of age at symptom onset is unclear. We investigated the relationship between these factors and functional disability in patients with recent-onset inflammatory polyarthritis (IP). Methods. A total of 3,666 patients (66% women) were registered with the Norfolk Arthritis Register between 1990 and 2008. Functional disability was assessed using the Health Assessment Questionnaire (HAQ), adjusted for age at HAQ completion. Linear random-effects models were used to examine HAQ score over time, by sex and age at symptom onset (early = age < 55 years, late = age 55-74 years, very late = age >= 75 years). Results. Women had higher HAQ scores over time than men (mean difference 0.29; 95% confidence interval [95% CI] 0.25, 0.34). Men with late-onset IP had lower baseline HAQ scores than men with early onset (mean difference -0.14; 95% CI -0.29, -0.001). Women had comparable baseline HAQ scores at all ages of onset. Both sexes showed the greatest rate of disability progression in patients with very late onset. Those with early onset had a steady level of disability over time. Adjustment for treatment received, comorbidities, and RA subgroup analysis produced results that were largely similar to the initial analysis. Conclusion. Female patients have higher HAQ scores than male patients; patients with early symptom onset show the smallest sex difference. Older age at symptom onset is associated with an increasingly steep trajectory of disability progression. The impact of sex on outcome is evident at baseline, whereas the impact of age at symptom onset becomes apparent during long-term followup.