Multi-tasking, Executive Function, and Functional Abilities in Older Adults with Type 2 Diabetes Mellitus
Rucker, Jason Lee
University of Kansas
Physical Therapy & Rehabilitation Sciences
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There is growing evidence that older adults with type 2 diabetes exhibit deficits in executive function, the set of processes responsible for planning, organizing, sequencing, and monitoring goal-oriented behavior. However, the specific nature of these executive impairments and their functional consequences in this population remain poorly understood. The primary purpose of this work was to determine whether older adults with type 2 diabetes demonstrated impairments in the executive process of multi-tasking when compared to their peers without diabetes, and to examine how multi-tasking abilities contributed to gait and other functional abilities in these individuals. We also sought to examine the integrity of other executive functions in those with diabetes, including the processes responsible for updating information, shifting between different tasks, inhibiting predominant responses, and organizing and recalling visuospatial and verbal data, and to explore their relationships to gait and functional ability. Chapter 2 describes the results of our pilot investigation, in which we administered a measure of multi-tasking, the Cognitive Timed Up and Go (cTUG), and a battery of 7 common executive function tests to 20 adults (age 40-65 years) with diabetes and diabetic peripheral neuropathy (DPN) and 20 individuals of similar age without diabetes. We found that those with DPN performed worse on the cTUG test, and also demonstrated poorer performance on executive function measures assessing visuospatial and verbal processing. Moreover, we observed that overall cognitive performance and symptoms of depression were significantly related to each other and to a measure of functional ability, whereas signs and symptoms of DPN were not associated with this functional measure. Although preliminary, this study illustrated the potential relationships between neuropsychological and physical function, and highlighted that functional impairments, fall risk, and disability in those with DPN is likely the result of a complex and multi-factorial process that extends beyond somatosensory and proprioceptive impairment. Building upon the data and experience we obtained from this pilot project, we next selected two instruments, the Walking and Remembering and Pursuit Rotor tests, in an effort to describe multi-tasking in much greater detail than was possible with the cTUG alone. As described in Chapter 3, these multi-tasking assessments, along with measures of single-task gait and self-reported functional ability and limitation, were administered to a group of 40 older adults (age 60 years and older) with type 2 diabetes and a group of 40 individuals without diabetes, pair-matched according to age, sex, education, and the presence or absence of hypertension. Our analysis of this data revealed that those with diabetes performed worse than comparison subjects when asked to multi-task while walking, appearing to preserve less critical task demands at the expense of gait stability. Interestingly, we observed little association between multi-tasking ability and our gait and functional measures. However, we did note rather striking relationships between these measures and symptoms of depression, physical activity level, and sleep quality. Overall, this data suggested that older adults with type 2 diabetes did exhibit disturbances that could impair safety when required to multi-task while walking. Furthermore, although these changes did not appear to substantially influence single-task gait mechanics or self-reported functional ability, we also found that commonly overlooked variables such as depression, physical activity, and sleep quality may make important contributions to everyday gait and function in this population. Examining these relationships in further detail, we next performed a series of regression analyses investigating the contributions of multi-tasking ability, depression, physical activity, and sleep quality to single-task gait speed and variability, and self-reported physical function and disability in our group with diabetes. Described in Chapter 4, this data demonstrated that there was little association between multi-tasking ability and single-task gait parameters or self-reported physical function and disability. However, our secondary analyses revealed significant adverse relationships between depression and gait variability and disability, between physical activity levels and walking speed and physical function, and between sleep quality and gait variability. Although often overlooked, factors such as depression, physical inactivity, and poor sleep quality are widespread in those with diabetes. Our analysis emphasizes the importance of appropriately identifying and treating such modifiable comorbidities, as well as the need for further research examining their relationships to different aspects of physical function and disability. Having completed our examination of multi-tasking, we turned our attention to exploring the integrity of other executive functions in those with diabetes. Alongside of our multi-tasking measures, we administered a battery of executive function tests assessing the processes of information updating, task shifting, response inhibition, and visuospatial and verbal processing and memory. Analysis of this data revealed that those with diabetes appeared to perform more poorly than comparison subjects on a specific measure of updating and a measure of visuospatial processing. However, we did not observe deficits on a second updating measure, or on any other executive test. Interestingly, although there was little relationship between executive performance and gait or functional abilities in the diabetes group, we observed a number of significant correlations between updating, shifting, and visuospatial memory and gait and function in the comparison group. These findings clearly emphasize the need for further research examining executive function in those with diabetes, and investigating how these processes contribute to physical deficits, falls, and/or disability in health and disease. In summary, the results of this body of work suggest that older adults with type 2 diabetes demonstrate significant changes in gait stability when required to walk while multi-tasking, and may also exhibit deficits in areas of executive function related to the ability to update information and process visuospatial stimuli. The influence of these and other executive functions on gait and functional ability remains unclear, but may differ between those with and without diabetes. Certainly, it appears that factors such as depression, physical activity, and sleep quality make important contributions to everyday function. Overall, our findings emphasize the need for further research investigating the physiological, psychological, and functional consequences of type 2 diabetes in older adults, and the diverse factors that may contribute to the higher incidence of falls, functional deficits, or disability in this high risk patient population.
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