Can Vitamin D3 Improve Cognitive Function in Individuals With Type 2 Diabetes? (THINK-D)
Phase: PHASE2
Conditions: Diabetes, Executive Dysfunction
Sponsor: Loyola University

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Protocol 
 
Protocol Title: Think-D: Can Vitamin D3 Improve Cognitive Function in Individuals with 
type 2 Diabetes?  
Protocol Acronym: THINK-D 
Protocol Version: 1.5 
Protocol Date: 03/01/2017 
Principal Investigator: Mary A. Byrn, PhD, RN 
Co-Investigators:  Sue Penckofer, PhD, RN; William Adams; PhD, Mary Ann Emanuele, 
MD 
 
Abstract 
 
Diabetes increases the risk of cognitive dysfunction.  The incidence of dementia is 1.5 to 
2.5 times higher in persons with diabetes than the general population. There is evidence 
that cognitive decline significantly impacts the ability to self-manage diabetes.   
Strategies to prevent cognitive decline in persons with diabetes has not been well studied.   
A recent study reported that in persons who had vitamin D deficiency, the risk for all-
cause dementia and Alzheimer’s was doubled.  Vitamin D receptors are located in the 
brain and deficiency of vitamin D has been reported to negatively affect the development 
of brain.  Therefore, providing vitamin D supplementation to improve cognitive function 
is worthy of study.   
 
We propose a small, randomized controlled trial to determine the effects of vitamin D3 
supplementation in persons with type 2 diabetes who have symptoms of cognitive 
impairment.  Participants will be randomized to receive either weekly vitamin D3 
supplementation (50,000 IUs) or a matching comparator (5000 IUs) for a period of three 
months. The study aims are to determine (1) the effect of vitamin D3 supplementation on 
cognitive function and (2) the effect of vitamin D3 supplementation on diabetes self-
management. A sample of persons with type 2 diabetes, who have a subjective complaint 
of a cognitive dysfunction or scoring at least one standard deviation below normal on a 
cognitive functioning screening test, have vitamin D levels less 30 ng/ml, are not 
depressed (as this impacts cognitive function), and do not have severe diabetes 
complication will be recruited. Participants will be phone screened and complete two 
baseline visits prior to randomization.  They will then have phone call and follow-up 
visits to assess (1) cognitive function using standardized tests to assess for executive 
function (2) serum measurements (HBA1c, fasting glucose, vitamin D levels, and 
cardiometabolic profile) and (3) surveys to assess cognitive function as well as self-
management behaviors.  
 
Study Aims 
 
Diabetes increases the risk of cognitive dysfunction.  The incidence of dementia is 1.5 to 
2.5 times higher in persons with diabetes than the general population (1).  There is 
evidence that cognitive decline significantly impacts the ability to self-manage diabetes 
(2).  Strategies to prevent cognitive decline in persons with diabetes has not been well 

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studied.  A recent study reported that in persons who had vitamin D deficiency, the risk 
for all-cause dementia and Alzheimer’s was doubled (3).  Vitamin D receptors are located 
in the brain, and deficiency of vitamin D has been reported to negatively affect the 
development of brain and impact both growth factor signaling and neural activity (4, 5).  
Therefore, providing vitamin D supplementation to improve cognitive function in persons 
with diabetes who are at greater risk for this comorbid condition is important.   
 
We propose a small, randomized controlled trial to determine the effects of vitamin D3 
supplementation in persons with type 2 diabetes who have symptoms of cognitive 
impairment.  Persons will be randomized to receive either weekly vitamin D3 
supplementation (50,000 IUs) or a matching comparator (5000 IUs) for a period of three 
months: 
 
Primary Aim:  To determine the effect of vitamin D3 supplementation on cognitive 
function for persons with type 2 diabetes. 
   
Primary Hypothesis:  Persons receiving weekly vitamin D3 supplementation (50,000 
IUs) will have improved cognitive function compared to those receiving the comparator 
(5000 IUs) at three months.  
 
Secondary Aim:  To determine the effect of vitamin D3 supplementation on diabetes 
self-management. 
 
Secondary Hypothesis:  Persons receiving weekly vitamin D3 supplementation (50,000 
IUs) will have improved self-management compared to those receiving the comparator 
(5000 IUs) at three months. 
 
The importance of this study is severalfold.  Vitamin D supplementation is a low-cost 
intervention (6), it has minimal side effects (7), and it could have high impact for persons 
with type 2 diabetes who suffer from cognitive impairment which can significantly affect 
diabetes self-management.   
 
Background and Significance 
 
Diabetes, cognitive impairment, and self-management.  Evidence indicates that 
diabetes is associated with cognitive impairment. In the Whitehall II cohort study, 
persons (n=5653) with a mean age of 54 years were followed for 10 years.  It was 
reported that for those with known diabetes there was a 45% faster decline in memory, a 
29% faster decline in reasoning, and a 24% faster decline in cognition compared to those 
with no diabetes (8).  In the National Health and Aging Trends study (n=7606 persons), 
self-reported diabetes was associated with immediate and delayed word recall and poorer 
memory (9). Cognitive impairment makes glycemic control challenging, because self-
management activities are cognitively demanding.  Executive function comprises 
cognitive skills needed for the execution of complex activities which can include self-
monitoring and daily management of diabetes.  Executive dysfunction is associated with 
poor glycemic control (10).  In a cross-sectional study of 169 patients who were 

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controlled with diabetes (HBA1c<7) and 104 who were inadequately controlled, it was 
found that any level of executive dysfunction significantly increased the odds of 
inadequately controlled diabetes (OR=3.6) compared to those who had the best executive 
functioning (11).  One study (n=1200) reported the frequency of executive dysfunction 
among elderly diabetics was 55% (12).   
 
Although aging is typically associated with cognitive decline, a recent report indicated 
that even in middle aged persons (n=1800, range 50 to 65 years of age) there was an 
association of type 2 diabetes and mild cognitive impairment for men (2.09) and women 
(1.69) (13).   A recent systematic review reported that glycemia, particularly high HBA1c 
was associated with cognitive dysfunction, however, only 10% of the variance in 
cognition was explained by this factor (14). Therefore, the need to explore other factors 
that may contribute to cognitive impairment is needed.      
 
Low vitamin D and cognitive impairment.  A meta-analysis of 14 observational 
studies, 3 prospective cohort studies, and 3 intervention studies has demonstrated that 
lower concentrations of vitamin D was associated with executive dysfunction (especially 
processing speed, mental shifting, and information updating) and that repletion was 
associated with improved executive functioning (15). More recently, participants from 
the United States Cardiovascular Health Study (n=1658 adults) who were followed 
prospectively for six years and were found to have a doubled the risk for dementia and 
Alzheimers if they were vitamin D deficient at baseline (3).  Persons with diabetes have 
been reported to have a higher incidence of vitamin D deficiency (16).  Although vitamin 
D replacement may not directly improve glycemic control (17, 18), there is preliminary 
evidence to suggest that it may improve depression in persons with diabetes (19, 20).  
Since depression may confound cognitive function (21, 22),studying vitamin D 
supplementation in persons with diabetes who are not depressed is important as it would 
provide preliminary evidence for its benefit in preventing or improving cognitive decline.  
 
 Pilot Study 
 
This proof of concept study examined whether vitamin D supplementation would 
improve diabetes symptoms and HBA1c in women with type 2 diabetes.  Fifty women 
with type 2 diabetes (mean age 54) who were depressed (Center for Epidemiologic 
Studies Depression Scale, CES-D > 16) and low vitamin D levels (<32 ng/dl) 
participated. A pre-post study design was used.  Women were given weekly vitamin D2 
(Ergocalciferol 50,000 IUs) for a period of six months.  The Diabetes Symptom 
Checklist, HBA1c, and vitamin D levels were collected at baseline, three, and six months.  
Ninety two percent of women (n=46) completed all visits.  At six months following 
supplementation, vitamin D levels increased as expected (p < .001), overall diabetes 
symptom score improved (p < .001), but there was no improvement in HBA1c.   
Although many diabetes symptoms were alleviated following vitamin D supplementation, 
those that improved the most from baseline to six months were: Difficulty concentrating 
(35%, p < .001), difficulty paying attention (31%,  p = .001), difficulty thinking clearly 
(30%, p = .001), moodiness (28%, p = .001), being easily irritated or annoyed (28%, p = 
.002), and overall sense of fatigue (28%, p = .001).  These findings indicate that 

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improvement in diabetes symptoms is independent of glycemic regulation following 
vitamin D supplementation.  This suggests that exploration of mechanisms to understand 
how vitamin D may affect cognitive functioning is needed.  Furthermore, the potential to 
engage persons with diabetes in self-care behaviors if cognitive function improves could 
be a potential benefit of this cost-effective treatment.    
 
Study Design 
 
Design.  This is a randomized, double-blind, active-comparator controlled trial of three 
months duration.  Participants will be randomly assigned to either 50,000 IU of vitamin 
D3 (n=31) or 5,000 IUs of vitamin D3 (n=31). Treatment Dose and Schedule: The 
supplements are administered once a week for three months. The dose of vitamin D3 
(cholecalciferol) (50,000 IUs) has been safely used (23, 24, 25).  The weekly dosing is 
being used to increase compliance to therapy (i.e., not having to remember to take it 
daily) and has been successful in treating other disorders (26).  To further increase 
compliance, participants will receive a weekly automated phone call reminder to take 
their supplement.  Vitamin D3 has been selected as the treatment since it is the natural 
form of vitamin D, the more widely used supplement, and now recommended for clinical 
practice (27).  The Institute of Medicine recommends 600 IUs of Vitamin D per day for 
individuals up to age 70 (28).  Thus, the 5,000 IUs dose will approximately follow that 
recommendation (600 IUs x 7 days= 4200 IUs) and be given once per week.  The use of a 
dose with the minimum recommended amount for comparison is consistent with other 
studies examining the benefit of vitamin D supplementation on health outcomes (7, 29).  
Bio Tech Pharmacal, Inc. will prepare the vitamin D3 supplements and follows Good 
Manufacturing Practices.  
 
The trial is appropriately registered on clinicaltrials.gov under an Investigational New 
Drug (IND) number (IND 126491).  Treatment Randomization: A permuted-block 
randomization list was developed by an independent statistician and retained by a 
research pharmacist at the study site.  These two staff members were independent from 
those involved with the conduct of the study.  The pharmacist uses the list to assign 
subjects to treatments.  Blinding. The study supplements are administered by the 
pharmacist in a blinded fashion during the study so that the patient and clinical site 
personnel are not aware of the patient’s assigned treatment. Treatment side effects and 
unblinding: All vitamin D levels and calcium levels are reviewed by the study medical 
monitor (Dr. Mary-Ann Emanuele) at baseline and at three months (study completion).  
Dr. Emanuele is notified if vitamin D levels are greater than 100 ng/ml or if they 
experience hypercalcemia.  In that case, patients are requested to return for repeat labs 
within one month of stopping therapy for monitoring purposes. 
 
Sample Enrollment Criteria 
   
A.  Enrollment Criteria.  Inclusion:  1) Women and men aged 18 to 75 years, 2) Having 
type 2 diabetes, 3) Having a subjective complaint of a cognitive dysfunction or scoring at 
least one standard deviation below normal on a cognitive functioning screening test (see 
Procedures and Measures), 4) Vitamin D level as measured by 25-hydroxyvitamin D (25-

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OH D) < 32 ng/mL (7), 5) Under the care of a healthcare provider, 6) Systolic blood 
pressure ≤160 and diastolic blood pressure ≤100.    Exclusion: 1) Persons with 
malabsorption problems (e.g., crohn’s disease) since this impacts vitamin D absorption 
(30), 2) Hypercalcemia since vitamin D may increase serum calcium (31, 32), 3) Use of 
vitamin D supplements in past 2 months and unwillingness to discontinue for one month 
prior to study, 4) Severe complications of diabetes (amputation, blindness, and dialysis) 
5) currently taking high dose steroids, 6) GFR < 60, 7) Creatinine > 1.2, 8) Having 
significant depressive symptoms (CESD> 16), 9) Having a history of bipolar depression, 
psychotic disorders, loss of consciousness greater than 5 minutes, or a current alcohol or 
substance use disorder, 10) Other serious medical conditions deemed significant by the PI 
or medical monitor, 11) Current use of cholinesterase inhibitors,  12) A new prescription 
for an anxiolytic within the past 12 months or a dose change to an anxiolytic in the past 
12 months (or anticipated dose change while in the study), or taking, kava kava, St. 
John’s Wort, or Ginkgo Biloba, 13) Pregnancy, 14) HbA1c >13%, 15) Having a history 
of kidney stones (unless origin know to be not calcium), 16) Taking more than 1200 mg 
of calcium per day which is consistent IOM guidelines, 17) Patients with known vascular 
disease (including stroke, TIA, lacunar infarcts,).  
 
Study Procedures 
 
Procedures.  There will be a phone screening, followed by a baseline visit to recruit and 
verify enrollment criteria.  A phone call interview will be conducted which entails study 
description, a screening for inclusion and exclusionary criteria, followed by the Center 
for Epidemiologic Scale (CES-D)  to ensure they are not depressed and screening for 
cognitive function using the Controlled Oral Word Association Test and Animal Naming 
Test (see Appendix for phone call screen and instruments). If the patient meets the 
inclusion criteria, they will be scheduled for a study visit. If they do not, they will be 
thanked for their time.  If participants do not meet the inclusion criteria because of 
depressive symptoms, a list of resources will be mailed to them.  At the first baseline 
visit, participants will come to the School of Nursing at Loyola (in Maguire).  The 
informed consent document will be reviewed by a qualified member of the research team.   
Participant’s capacity to give written informed consent will be evaluated using the 
“Evaluation to Sign an Informed Consent for Research” form (attached in Appendix).  If 
a participant is unable to provide informed consent, they will be ineligible to participate.  
After informed consent is obtained, blood will be drawn (glucose, hemoglobin A1c, 
vitamin D, calcium, and inflammatory markers).  Calcium will be measured in order to 
follow published guidelines when initiating vitamin D at this dose (50,000 IU) to assess 
for a therapeutic level (7, 34). Also, physical measures (height, weight, and blood 
pressure) will be collected. Study subjects will be provided with breakfast or a snack and 
reminded to take their prescribed medications (if needed).  Next, the cognitive 
functioning tests will be administered by a member of the research team. This will 
include an evaluation of the premorbid intellect using the word pronunciation test from 
the Wide Range Achievement Test-IV.  A questionnaire booklet will be completed with 
measurement of self-care behaviors, and the researcher will review the questionnaires for 
missing data to determine whether items were skipped or not answered due to the 
participant’s choice.  The questionnaire booklet will include the Patient Health 

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Questionnaire 9 tool (9 items).  If the patient answers positively to item #9 on this tool 
which reads, “thoughts that you would be better off dead or hurting yourself in some 
way,” then he or she will be assessed for active suicide ideation using a form that is 
approved for suicidal ideation in the Sunshine Study 2 Protocol (see attached form).  If 
the patient has active suicidal ideation, Dr. Halaris, psychiatrist will be contacted.  If the 
patient has active suicidal ideation and is deemed to be in need of immediate psychiatric 
care, a member of the research team will escort the patient to the emergency room.  In 
addition, the patient will be given a list of mental health resources and the patient will not 
be eligible to participate in the study.  The baseline visit will be completed with 
collection of vital signs and a nursing physical assessment administered by a qualified 
member of the research team. The total amount of time for the baseline visit will be 2-3 
hours.  Once enrollment criteria have been met, the second baseline visit with a qualified 
member of the research team will be scheduled to dispense the Vitamin D supplement to 
the participant.  At this visit, the six cognitive functioning tests will be administered again 
in order to wash-out any practice effects.  The weekly medication administration 
schedule and all subsequent contacts (phone and scheduled visits) will be reviewed.  
Participants will be informed that, at three months, they will return for physical 
measurements and evaluation of cognitive functioning and self-care behavior.  They will 
be told that in six weeks a qualified member of the research team will conduct a formal 
phone call follow-up, where they will be asked about medication compliance and side 
effects and screening for cognitive function using the Controlled Oral Word Association 
Test and Animal Naming Test.  Upon completion of these verbal and written instructions 
and a negative pregnancy test (if necessary), the patient will be provided with the 
randomized vitamin D3 medication.  Following dispensing directions, a qualified member 
of the research team will ask the subject if they have any questions.   The second visit 
will take two hours or less.  At their three-month visit, the exact protocol from baseline 
visit (labs, questionnaires, and cognitive functioning tests) will be followed. The three 
month visit will take 3 hours or less. A qualified member of the research team will 
request the study medication bottle to estimate drug accountability by counting any 
remaining pills.  To forestall attrition and enhance compliance, we will capitalize on 
retention strategies that have proven successful in Dr. Penckofer’s current NIH study 
(RO1NR013906), which include free parking and compensation for participants’ time. 
Participants will be compensated in a stepped manner: ($20 at first baseline visit, $25 at 
second baseline visit, and $30 for completing the study at the three month visit).  After 
the patients have completed the study, a letter (see attached letter) will be sent to them 
which includes the results of their HbA1c and Vitamin D levels.  
 
Table 1: Scheduled Activities 
 
 
Screening 
Week 0 
Week 2 
Week 8 
Week 13 
Depression Screen 
X 
 
 
 
 
Demographics 
X 
X 
 
X 
X 
Cognitive Tests 
X 
X 
X 
X 
X 
Questionnaires 
 
X 
 
 
X 
Vitals 
 
X 
 
 
X 
General Nursing Physical  
X 
 
 
 

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Blood Draw 
 
X 
 
 
X 
Adverse Event Log 
 
X 
X 
X 
X 
Dose Management Log 
 
 
X 
X 
X 
Concomitant Medication 
Log 
 
X 
X 
X 
X 
 
  
4. Measurements.   
A. Labs will be measured for each time point by Quest Laboratories which is accredited 
by the College of American Pathologists (CAP) and Clinical Laboratory Improvement 
Amendments (CLIA). Serum vitamin D will be measured by liquid 
chromatography/tandem mass spectrometry (LC-MS/MS) which is the standard for the 
measurement of vitamin D and its components.  This method provides a total 25 
hydroxyvitamin D (25 OH- D) which includes 25 (OH) D2 and 25 (OH) D3.  Thus, we 
will be able to determine the effectiveness of vitamin D3 supplementation. Calcium will 
be measured using a cardiometabolic profile.  The hemoglobin A1c will be assessed 
using the DCA analyzer which is the practice in our diabetes center.  Also, inflammatory 
markers will be collected.  Potential confounders for vitamin D include sun exposure and 
diet and will be measured as follows: (1) Sun Exposure: Season of study enrollment will 
also be recorded and the Cancer Sun Exposure Tool which is 14 items and assesses sun 
exposure and use of sunscreen (35), (2) Dietary Intake:  The Block Calcium and 
Vitamin D Screener will be used.  This tool was developed from the NHANES 1999-
2001 dietary recall data. It includes 19 food items, 3 supplement questions, and questions 
to adjust for food fortification practices (36).   
 
B. Self-Management measures include:  (1) Diabetes Self-Care Inventory (15 items) 
assesses a patient’s perceptions of the degree to which they adhere to treatment 
recommendations for diabetes self-care (1= never do it to 5= always do it).  This tool 
does not presume that all individuals have the same treatment prescription and thus is 
able to assess adherence to different treatment regimens (e.g., insulin or not taking 
insulin) (37, 38). (2) Diabetes-Related Distress (PAIDS, 20 items) measures the current 
burden of diabetes and its treatment. The responsiveness of the tool to detect changes in 
distress has also been established using data from seven prospective diabetes intervention 
studies (39).  
 
C. Cognitive Functioning measures include six instruments.   (1) The Controlled Oral 
Word Association Test (COWAT) is a measure of verbal fluency that assesses the 
ability to initiate and maintain effort and requires participants to rapidly produce words 
beginning with certain letters (40).  This verbal fluency task taps the function of the 
dorsolateral prefrontal cortex, a prime target of the atrophy observed in the brains of 
decedents with diabetes.  (2)The Animal Naming test is similar to COWAT, but it 
assesses semantic fluency rather than phonemic fluency.  Verbalizing a large amount of 
words indicates superior performance. (3) The Letter Number Sequencing is a test in 
which a string of alpha-numeric characters are read aloud to the participant, and he/she 
has to mentally rearrange them and say back all the numbers in numerical order followed 
by all the letters in alphabetical order (41).  Few errors indicate superior performance. 

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(4)Stroop Interference Test involves having the participant read color words, name 
colors, and complete an interference condition (i.e., the words are printed in colored ink 
that does not correspond to the written word).  As quickly as possible, the subject must 
ignore what the word actually says and, instead, name the color of the ink in which the 
word is printed (42).  High scores indicate superior performance. (5) Digit Symbol 
Modalities Test assesses several skills including motor persistence, sustained attention, 
response speed, and visuomotor coordination (43).  Participants must draw in numbers 
that match symbols as quickly as possible for 90 seconds.  Higher scores indicate 
superior performance. (6) Trail Making Test Parts A and B assesses psychomotor 
processing speed and cognitive flexibility (44).  This test requires the participant to view 
a series of randomly arranged numbers and letters on a page.  Participants must draw a 
line alternating between numbers and letters in numerical and alphabetical order (e.g., 1-
A-2-B-3-C and so on), as quickly as possible.  Shorter time-to-completion and few errors 
indicates superior performance. (7) Hopkins Verbal Learning Test revised assesses 
verbal learning and memory.  The test asks participants to recall a series of 12 words after 
a period of 20 to 25 minutes. 
 
D. Other Factors that contribute to the health of individuals with diabetes include (1) 
Pittsburgh Sleep Quality Index (19 items) measures sleep quality (45), (2) the Perceived 
Stressor Scale (10 items) measures stress (46), (3) social functioning will be measured 
using the Social Adjustment Scale-Self Report (24 items) (47), (4) exercise using the 
Godin Leisure Time Exercise questionnaire (2 items) (48), and (5) the Endicott Work 
Productivity Scale (25 items) (49). (6) the Patient Health Questionnaire 9 (PHQ9) (9 
items), will be used to assess for depression at the baseline visit only.   
See attached appendix for all questionnaires and instruments.  
 
Recruitment Procedures 
 
For recruitment of study participants, we will be using the database of Dr. Penckofer 
which has over 350 patients who have expressed interest to participate in diabetes 
research in the past few years.    See attached letter that will be sent to potential study 
participants.  In our current work (LU 204197), we have been able to reach out to over 
1200 patients thus far.  Given our previous work, patient recruitment should not be an 
issue for this pilot study.   Also, an approved flyer through Marketing will be 
distributed at Loyola University Medical Center outpatient centers, places of business 
who have provided approval, and professional meetings, and 3) A qualified member of 
the research team will be present at the endocrinology outpatient clinic to provide 
information about the study to potential participants. 
 
Informed Consent  
Informed consent will be obtained by a qualified member of the research team  when the 
patient comes to the School of Nursing (Maguire) for the first in-person visit. 
 
Safety Monitoring Plan 
 

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A monitoring plan has been established to ensure that the data remain confidential and 
that any harm from the intervention is minimized.  The research team (including principal 
investigators, co-investigators, and qualified members of the research team) will meet 
once a week to assess the activities of the study, including the review of any adverse 
events, serious adverse events, or noncompliance with the procedures of the protocol.  
 
Study Monitoring Criteria: 
 
The research team will specifically review (1) number (if any) patients who develop 
vitamin D levels greater than 100 ng/mL or symptoms of vitamin D toxicity, (2) number 
(if any) patients who developed hypercalcemia, (3) number of patients (if any) who 
develop systolic blood pressure readings >160 mmHg or diastolic >100 mmHg, (4) 
number of patients (if any) who develop an increase in creatinine of 25% or more, and (5) 
patients with significant worsening cognition. 
 
 
Individual Stopping Criteria 
 
The research team will review data related to individual stopping criteria, as detailed 
below.  The medical monitor may recommend modifications to individual stopping rules 
if additional safety concerns arise during their continuing review of the study data.  
 
• If Vitamin D levels exceed 100 ng/mL at any time 
• If a participant’s CA >10.5 at any point  
• If a participant develops a kidney stone  
• Significant worsening cognition 
 
Worsening cognition will be treated as an adverse event.  Participants will be referred to 
an appropriate healthcare provider (i.e. Neuropsychologist, Clinical Psychologist, 
Psychiatrist, or Neurologist) by a member of the research team.  
 
Study Stopping Criteria 
 
The medical monitor may recommend stopping the study for the following reasons: 
• The data show a significantly increased risk of serious adverse effects deemed 
related to the study supplement in one of the treatment groups 
• It becomes clear that successful completion of the study is not feasible (e.g. there 
is an excess of patient dropout, missing data, lack of recruitment, etc) 
 
In addition, termination or modification may be recommended for any other perceived 
safety concern based on clinical judgment, including but not limited to a higher than 
anticipated rate for any component of the primary endpoint, protocol failures resulting in 
adverse events, or unexpected adverse events.    
 
Analysis Plan 
 

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Statistical Methods: Power 
 
 
A meta-analysis based on a sample size of N = 7,688 by Etgen et al. (2012) was 
used to determine a sample size with suitable power for this trial.  In their study, 
individuals with insufficient vitamin D were nearly three times (95% CI:  1.91 – 3.00) 
more likely to experience executive dysfunction than individuals who were vitamin D 
sufficient.  Our study is powered to test the null hypothesis that performance on a battery 
of executive functioning tests is equal between individuals receiving high dose vitamin D 
therapy and those receiving low dose vitamin D therapy.  These executive function scores 
are assumed to be standard scores (µ=100, SD=15). 
 
With a proposed total sample size of 62 subjects assigned to the 50,000 IU and 
5,000 IU dose treatment arms using a 1:1 allocation, the study has power of 81.1% to 
yield a statistically significant result.  This computation assumes a two-sided alpha level 
of 0.05, that the mean difference between the two groups is less than one standard 
deviation (mean difference = 11.0) which corresponds to expected means of µ = 96 for 
the 50,000 IU group and µ = 85 for the 5,000 IU dose group, and that the common 
within-group standard deviation is one standard deviation (or 15 points).  This effect was 
selected as the smallest effect that would be important to detect, in the sense that any 
smaller effect would not be of clinical or substantive significance.  In order to account for 
attrition, 80 participants are planned to enroll into the study. 
   
Statistical Analysis Plan 
 
Summary frequencies will be reported by treatment allocation for all nominal 
baseline characteristics, including sex, race, ethnicity, marital status, season of first dose, 
and physical activity level.  Summary statistics will be similarly reported as mean with 
standard deviation for normally distributed demographics (i.e., age, body mass index, 
blood pressures and heart rate, and CES-D score), while median with interquartile range 
will be reported for other summary measures including PHQ-9 score, WRAT-IV reading 
sub-score, years of education, and laboratory values (i.e., vitamin D level, HbA1c, 
glucose, creatinine, and calcium). 
 
Regarding performance on the executive functioning assessments, linear mixed-
effects models will be used to estimate the mean change in participants’ standardized 
scores as a function of elapsed time since baseline, treatment assignment, and their 
interaction.  In this study, patients will contribute multiple scores to the analysis and 
random intercepts will be allowed for each patient to account for their within-subject 
correlation using an unstructured covariance structure.  Regarding model fit, linearity and 
normality will be assessed using residual and QQ plots, respectively, while outliers will 
be assessed using box plots.  A similar approach will be used to assess performance on 
assessments of language and memory functioning. 
 
Regarding change in quality of life and functioning self-report measures (i.e., the 
SAS-SR; SCI-R; PAID; EWPS; PSQI; MOS; and PSS), each participant’s baseline score 
will be subtracted from his/her week 13 score.  Subsequently, an independent samples t-

11 
 
test will be used to compare this change score between participants assigned to the high 
dose versus those assigned to the low dose.  In these comparisons, the distribution of 
survey scores will be assessed for normality using QQ plots and for outliers using box 
plots.  When survey scores are not normally distributed, an exact version of the Wilcoxon 
rank-sum test may be used to confirm parametric conclusions. 
 
Finally, summary frequencies will be reported for all reported adverse events 
during the trial by treatment allocation.  This includes the number of affected individuals 
at risk for the adverse event as well as the number of times the adverse event was 
reported.  All analyses will be completed using SAS version 9.4 (Cary, NC). 
 
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