Activity limitation in rheumatoid arthritis correlates with reduced grip force regardless of sex:: The Swedish TIRA Project

Objective. To evaluate activity limitations 3 years after diagnosis of early rheumatoid arthritis (RA) in relation to grip force and sex. Methods. A total of 217 patients, 153 women and 64 men, with recent-onset RA were included. Activity limitations were reported using the Health Assessment Questionnaire (HAQ) and the Evaluation of Daily Activities Questionnaire (EDAQ). The relationships between activity limitations versus grip force (measured by the Grippit), walking speed, functional impairment, grip ability, pain, plasma C-reactive protein, the 28-joint disease activity score and its components, the physician's global assessment of disease activity, and sex were analyzed by partial least squares (PLS). Results. Women had significantly lower grip force and more activity limitations (HAQ and EDAQ) than men. The PLS analyses demonstrated that grip force was the strongest regressor of activity limitation, closely followed by walking speed. However, within subgroups based on grip force (group 1 = grip force < 114 N, group 2 = 116-206 N, group 3 = 214-321 N, group 4 = grip force > 328 N) and including sexes, women and men had corresponding degrees of activity limitation as reported by the HAQ and EDAQ. Conclusion. Our results indicate that the more pronounced activity limitations seen in women with RA, as compared with men, may be explained by lower grip force rather than sex.