The psychosocial and cognitive impact of longstanding 'benign' multiple sclerosis

Background: Benign multiple sclerosis (BMS) is typically defined using the Expanded Disability Status Scale (EDSS), which relies heavily on ambulation. We set out to examine important psychosocial and cognitive outcomes in patients with longstanding BMS compared with patients who had recently progressed to 'no longer benign' (NLB). Methods: A previously reported cohort of BMS (EDSS <= 3 at 20 years disease duration) were re-assessed 25-30 years post-onset. Patients remaining benign (EDSS <= 3 at re-assessment) were compared with those NLB for: depression (Beck Depression Inventory), fatigue (Modified Fatigue Impact Scale), health-related quality of life (MSQoL-54), cognition (Rao's Neuropsychological Screening Battery), and employment status. Results: A total of 75% (66/88) of the original cohort were located. A total of 61 patients were re-assessed. Twenty-five patients (41%) had progressed in EDSS and were NLB. Compared with benign patients, those NLB were more likely to have: significant fatigue (15/36 [42%] vs. 18/25 [72%], p = 0.019); poorer physical functioning (mean MSQoL-54 = 67.30 vs. 50.89, p = 0.002); an MS-related negative change in employment status (13/36 [36%] vs. 21/25 [84%], p < 0.0001) and cognitive impairment (3/28 [11%] vs. 5/19 [26%]; trend only, p = 0.317). Depression and mental health quality if life differed little between the benign and NLB patients (p > 0.6). Conclusions: Despite remaining benign for 20 years, a significant proportion of patients progressed with further follow up. While neither depression nor patient-reported mental health quality of life was associated with EDSS progression, patients with longstanding 'benign' MS (EDSS <= 3 for 25+ years) had less fatigue, better physical quality of life and employment outcomes and infrequent cognitive impairment. Remaining benign over the long term, as defined by the EDSS, carried some advantages beyond ambulation.