To investigate the relationships between self-reported cognitive abilities, psychological symptoms and neuropsychological outcomes in PSS.
Patients with Primary Sjogren's syndrome (PSS) and healthy controls completed a comprehensive neuropsychometric battery and questionnaires: the Centers for Epidemiological Scale-Depression, the Profile of Fatigue-mental domain (Prof-M) for cognitive symptoms, Fatigue Severity Scale, and the Short-Form McGill Pain Questionnaire.
Female patients with PSS (N = 39) were similar to controls (N = 17) in estimated premorbid intellectual function, age and education. Depression (P = 0.002), cognitive symptoms (P = 0.001), fatigue (P = 0.000003), and pain (P = 0.024) scores were greater in the patient group. Patients with PSS demonstrated inferior performance relative to controls in psychomotor processing (P = 0.027) and verbal reasoning (P = 0.007). Patients with PSS with and without depression had similar performance on multiple tests, but depressed patients had significantly lower scores for executive function (P = 0.041). Cognitive symptoms correlated with verbal memory (P = 0.048), whereas pain correlated with executive function measures (Stroop, P = 0.017) and working memory (Trails B, P = 0.036). In the regression model, depression and verbal memory were independent predictors that accounted for 61% of the variance in cognitive symptoms.
The Prof-M is a simple self-report measure which could be useful in screening PSS subjects who may benefit from detailed psychometric evaluation. Our results are consistent with the hypothesis that depression and verbal memory impairment are overlapping but independent aspects of neural involvement in PSS. While pain and depression are significant confounders of cognitive function in PSS, this study suggests that impaired verbal reasoning ability in PSS is not attributable to pain or depression.