MULTI-TASKING, EXECUTIVE FUNCTION, AND FUNCTIONAL ABILITIES IN OLDER ADULTS ...

216 Pages·2014·2.07 MB·English

MULTI-TASKING, EXECUTIVE FUNCTION, AND FUNCTIONAL ABILITIES IN OLDER
ADULTS WITH TYPE 2 DIABETES MELLITUS

BY

Jason Lee Rucker
MSPT, University of Kansas Medical Center
BS, Kansas State University, Kinesiology

Submitted to the graduate degree program in Rehabilitation Science and the Graduate
Faculty of the University of Kansas in partial fulfillment of the requirements for the
degree of Doctor of Philosophy.

______________________________
Patricia Kluding, PT, PhD
Chairperson

______________________________
Jeffrey Burns, MD, MS

______________________________
Jonathan Mahnken, PhD

______________________________
Joan McDowd, PhD

______________________________
Carla Sabus, PT, PhD

Date Defended: January 30th, 2014
The Dissertation Committee for Jason Lee Rucker
certifies that this is the approved version of the following dissertation:

MULTI-TASKING, EXECUTIVE FUNCTION, AND FUNCTIONAL ABILITIES IN OLDER
ADULTS WITH TYPE 2 DIABETES MELLITUS

_____________________________
Patricia Kluding, PT, PhD
Chairperson

Date Approved: January 31st, 2014

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Abstract
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
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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
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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
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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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Acknowledgements

This work is dedicated to my father, Dr. Jim D. Rucker.
I love and miss you Dad.

My most sincere gratitude to my mentor, Dr. Patricia Kluding, and the members of my
committee, Dr. Jeff Burns, Dr. Joan McDowd, Dr. Jonathan Mahnken, and Dr. Carla
Sabus. And to Dr. Lisa Stehno-Bittel, Dr. Irina Smirnova, Dr. Sandra Billinger, Dr.
Stephen Jernigan, Amanda Britton, DPT, Nora Utech, DPT, and my friends and
colleagues in the Department of Physical Therapy and Rehabilitation Science and the
Georgia Holland Research Laboratory past and present. I could not have been blessed
to learn from and work with a more talented, supportive, and incredible group of
individuals.

And finally, to my family: Ginger, Nico, Mom, Jill, Jon, and Nora. I can never thank you
enough for the love and support you have given me. I love and appreciate you more
than words could ever express.
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Table of Contents
Acceptance Page ………………………………………………………………. ……. ii
Abstract ……………………………………………………………………………….. iii
Acknowledgements …………………………………………………………… ……. iv
Table of Contents ……………………………………………………………………. viii
List of Tables and Figures ………………………………………………………….. xv

Chapter 1 Introduction
1.1 Abstract …………………………………………………………. 2
1.2 Overview ………………………………………………………… 3
1.3 Executive Function: Concept and Processes ………… …….. 4
1.3.1 Dividing Attention (“Multi-tasking”) .............................. 7
1.3.2 Monitoring and Updating Information (“Updating”) ….. 10
1.3.3 Mental Set and Task Shifting (Shifting”) ……………… 10
1.3.4 Response Inhibition (“Inhibition”) ……………………… 11
1.3.5 Visuospatial Function …………………………………... 12
1.4 Executive Function and Type 2 Diabetes Mellitus ………….. 14
1.5 Pathophysiological Mechanisms of Executive Dysfunction in
Diabetes Mellitus …………….………………………………. 15
1.5.1 Neuroanatomical Changes ……………………………... 17
1.5.2 Role of Glycemic Control ……………………………….. 17
1.5.3 Role of Vascular Disease ………………………………. 18
1.5.4 Role of Insulin Resistance ……………………………… 19
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1.6 Executive Function, Diabetes, and Gait ………………………. 21
1.7 Executive Function, Diabetes, and Functional Abilities …….. 25
1.8 Clinical Implications …………………………………………….. 26
1.9 Conclusions ……………………………………………………… 28
1.10 Specific Aims and Hypotheses ………………………………… 28
1.11 References ……………………………………………………….. 30

Chapter 2 Pilot Study of Multi-tasking and Executive Function in Adults
with Diabetic Peripheral Neuropathy
Chapter 2 Preface ………………………………………………………………………. 48
2.1 Abstract …………………………………………………………... 50
2.2 Introduction ……………………………………………………… 51
2.3 Methods ………………………………………………………….. 52
2.3.1 Study Design and Sample ……………………………... 52
2.3.2 Procedures ………………………………………………. 53
2.3.3 Measures ………………………………………………… 54
2.3.4 Statistical Analysis ……………………………………… 56
2.4 Results …………………………………………………………… 57
2.4.1 Sample Characteristics ………………………………… 57
2.4.2 Peripheral Neuropathy Measures …………………….. 58
2.4.3 Timed Up and Go Performance ………………………. 59
2.4.4 Cognitive Timed Up and Go Performance …………… 59
2.4.5 Executive Function Measures …………………………. 63
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2.4.6 Relationships between Neuropsychological Function, DPN
Measures, and TUG Performance ……………………. 63
2.5 Discussion ………………………………………………………. 64
2.6 Conclusions …………………………………………………….. 70
2.7 References ………………………………………………………. 70

Chapter 3 Multi-tasking in Older Adults with Type 2 Diabetes Mellitus
Chapter 3 Preface ………………………………………………………………………. 76
3.1 Abstract …………………………………………………………... 78
3.2 Introduction ……………………………………………………… 79
3.3 Methods ………………………………………………………….. 81
3.3.1 Study Design and Sample ……………………………... 81
3.3.2 Procedures ………………………………………………. 82
3.3.3 Measures ………………………………………………… 83
3.3.4 Statistical Analysis ……………………………………… 88
3.4 Results …………………………………………………………… 90
3.4.1 Sample Characteristics ………………………………… 90
3.4.2 Multi-tasking Performance ……… …………………….. 90
3.4.3 Quantitative Gait Analysis ………..……………………. 96
3.4.4 Late Life Function and Disability Index ……..………… 96
3.4.5 Relationships between Multi-tasking Performance and Gait
and Functional Ability …………………………………. 98
3.4.6 Other Relationships ………………….…………………. 98
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