Association between cognitive impairment and olfactory deficits in systemic lupus erythematosus without major neuropsychiatric syndromes

Objective The aim of the study was to investigate the utility of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), evaluate cognitive deficits in systemic lupus erythematosus (SLE) patients and examine the relationship between cognitive and olfactory functions. Methods 55 SLE patients and 50 healthy controls were administered by RBANS including five indexes: immediate memory (IMME), visuospatial/constructional (Vis/Con), language (LANG), attention (ATT), and delayed memory (DEME). Olfactory functions were evaluated by computerized testing including three stages of smell: threshold (THR), identification (ID), and memory (ME) of different odors. The disease activity and cumulative damage were assessed by the SLE Disease Activity Index 2000 (SLEDAI-2K) and the Systemic Lupus International Collaborating Clinics (SLICC)/American College of Rheumatology (ACR) Damage Index (SDI). Results SLE patients exhibited significant lower total RBANS scores, IMME, Vis/Con, ATT, and DEME index scores than healthy controls ( p < 0.01 for all and p = 0.027 for attention). Reduced RBANS scores were associated with several organ involvement and autoantibodies. SLE patients with higher SLEDAI-2K scores or with accumulated damage (SDI≥1) showed decreased RBANS scores. All the olfactory scores in SLE patients were significantly decreased than controls ( p = 0.001). Patients had higher proportion of anosmia (8.57% vs 0%) and hyposmia (28.58% vs 5.72%) than controls (χ2 = 10.533, p = 0.015). Multivariable regression analysis revealed that olfactory functions had a positive effect on RBANS index scores. Olfactory memory and total scores were significantly correlated with the DEME (r = 0.393, p = 0.021) and total scores (r = 0.429, p = 0.011). Conclusion This study indicates that significantly cognitive and olfactory functions are impaired in SLE patients. The RBANS is a potentially useful instrument for evaluating neuropsychological status in SLE. Physicians are encouraged to perform routine screening in SLE patients to detect subtle cognitive dysfunction.