Background: Cognitive impairment can occur early in the course of multiple sclerosis (MS) and worsen progressively over time, impacting patients quality of life and employability. We previously identified a threshold score of 44 correct responses on a digital processing speed test (PST), used to assess cognition, as predictive of employment status. Understanding how MS patients scores impact performance of activities of daily living (ADL) may aid in counseling during cognitive assessments.
Objectives: Describe difficulty in performing instrumental (IADL) and cognitive (CADL) ADLs by MS patients with PST scores ?44 vs >44.
Methods: The analysis included 1108 adult MS patients from the US aged ?60 yrs and with education level ?8 yrs who were enrolled in a study assessing the feasibility of digitally collected neuroperformance outcome measures. Patients completed a PST representing a digital version of the Symbol Digit Modalities Test (SDMT) and a validated ADL questionnaire. The 23-item IADL and 19-item CADL components were each scored within a 7-day recall period on a 4-level response with 2 additional non-applicable options. Pearson coefficients were calculated between PST and CADL/IADL. Cross-sectional aggregate Raw and Rasch baseline ADL scores were compared in patients with PST ?44 or >44, adjusting for age, sex, education, manual dexterity, and walking speed. Individual item IADL and CADL scores were compared using multivariate generalized linear models.
Results: PST was significantly correlated with CADL (-0.27, p<0.0001) and IADL (-0.34, p<0.0001) scores. Aggregate scores were different for CADL (p<0.001) but not IADL (p=0.2) between patients with PST ?44 (n=313) vs PST>44 (n=795). Analyses of individual items showed that 7/23 (30%) IADL and 12/19 (63%) CADL items were significantly worse if PST ?44. The affected items represented activities requiring following directions, managing finances, planning and organization, driving, and phone conversations; not affected items were activities requiring memorization, moderate or heavy physical work, and attendance of crowded events.
Conclusions: A PST threshold of 44, previously associated with employment status, is also reflective of differential difficulties in cognitive ADLs in people with MS, especially as it relates to activities requiring executive abilities but not memorization. Routine cognitive screening may be valuable for appropriate patient counseling on planning daily activities and employment.