The influence of illness and variables associated with functional limitations in Chinese patients with ankylosing...

To assess the effect of illness and the functional outcome of Chinese patients with ankylosing spondylitis (AS), and to identify variables associated with a poor functional outcome.

A cross-sectional study was performed in 314 patients with AS who participated in a postal survey on the effects of illness on work capacity, functional limitations, and explanatory variables. Functional limitations were assessed using the Bath AS Functional Index (BASFI). Explanatory variables included sociodemographic characteristics and clinical features. Linear regression analyses were performed to identify variables associated with functional impairment.

The mean +/- standard deviation (SD) age of the patients was 44 +/- 11 years, with a mean disease duration of 19 +/- 11 years. The median BASFI was 3 (IQR 1.0-5.3). Twenty-three percent reported AS-related work disability after a median of 11 (IQR 2-17) years. Multivariate analysis identified low family income, education level, disease duration, Bath AS Disease Activity Index (BASDAI) score, and patient's global score as factors associated with functional impairment. In the subgroup of patients with disease duration < 20 years, low monthly income, juvenile onset, and high patient global score were associated with functional impairment; whereas in the subgroup of patients with disease duration > or = 20 years, less education, longer disease duration, and history of peripheral joint pain were associated with functional impairment. BASDAI was associated with functional impairment in both subgroups.

AS in Chinese patients had significant social and economic impact. Poor socioeconomic background, long disease duration, and high disease activity level were associated with functional impairment.