Dual-task interference during obstacle negotiation in people with chronic stroke is modulated by cognitive task type and complexity

Introduction: Dual-task interference (DTI) can affect cognition and/or locomotion in people with chronic stroke when either performing or attempting to perform two tasks simultaneously. Despite the fact that environmental obstacles are frequently encountered when walking in community contexts, previous research studies have largely focused on examining DTI during level-ground walking scenarios.
Objective: This cross-sectional study aimed to investigate the influence of cognitive task type and complexity on dual-task walking performance among people with chronic stroke.
Methods: Ninety-three individuals with chronic stroke [age=62.4(6.7)years] participated. During each dual-tasking scenario, an obstacle-crossing mobility task was performed concurrently with 1 of 5 distinct cognitive tasks (i.e., category naming, auditory discrimination, clock test, serial-subtractions, shopping list recall) of low and high complexity level, yielding a total of 10 dual-task testing scenarios. Dual-task effect (DTE = single-task - dual-task / single-task) was calculated for walking distance (mobility DTE) and the number of accurate responses given (cognitive DTE).
Results: Of all the potential DTI patterns, "mobility interference" (i.e., reduced walking distance without a decline in cognitive performance) was the most commonly observed. We observed large interaction effects for cognitive task type and complexity, which influenced both mobility (ηp2=0.12, p<0.001) and cognitive performance during dual-task obstacle crossing (ηp2=0.10, p<0.001). Among the distinct cognitive tasks, serial-subtraction demonstrated the greatest interference in terms of cognitive performance (MD=-10.4 to -29.5%, p<0.05).
Conclusions: The degree and pattern of DTI observed were influenced by the interaction between cognitive task type and complexity level. In addition to these factors, individual differences in the level of arousal, subliminal task prioritization, cognition and mobility impairment may also influence DTI patterns. Standardization of clinical assessments which evaluate these distinct cognitive domains are needed to accurately profile DTI during ambulation in people with stroke.