Cognitive dysfunction in systemic lupus erythematosus is independent of active disease.

OBJECTIVE: To determine whether disease activity in organ systems other than the central nervous system (CNS) contributes to impaired neurocognitive functioning in patients with systemic lupus erythematosus (SLE) without current major neuropsychiatric problems. METHODS: A cross sectional study of 90 consecutive female patients with SLE. Neuropsychological status was evaluated with a comprehensive 2.5 h battery of tests. Disease activity was evaluated by the Lupus Activity Criteria Count (LACC) in all patients and the SLE Disease Activity Index (SLEDAI) in a subset of 20. Involvement of particular organ systems was identified with reference to American Rheumatism Association criteria. RESULTS: Sixty-eight of the 90 patients showed no active CNS involvement at the time of testing. Of these 68, 36 (53%) were impaired according to quantitative criteria alone. However, the association between cognitive impairment and disease activity was not significant using either LACC or SLEDAI as the measure of disease activity. Further, the group with active disease did not show generally poorer performance in specific areas of cognitive function than the group with inactive disease at the time of testing. The likelihood of significant cognitive impairment was not increased in the presence of involvement of any of the organ systems reviewed by the LACC. CONCLUSION: These findings substantiate our working hypothesis that cognitive impairment in SLE reflects an immune mediated compromise of an underlying neural substrate, rather than the non-specific effects of chronic illness or its treatment.