Effect of vitamin D on cognitive decline: results from two ancillary studies of the VITAL randomized trial

Abstract

Low vitamin D levels have been associated with cognitive decline; however, few randomized trials have been conducted. In a trial, we evaluated vitamin D3 supplementation on cognitive decline. We included participants aged 60+ years (mean[SD] = 70.9[5.8] years) free of cardiovascular disease and cancer in two substudies in the VITAL 2 × 2 randomized trial of vitamin D3 (2000 IU/day of cholecalciferol) and fish oil supplements: 3424 had cognitive assessments by phone (eight neuropsychologic tests; 2.8 years follow-up) and 794 had in-person assessments (nine tests; 2.0 years follow-up). The primary, pre-specified outcome was decline over two assessments in global composite score (average z-scores of all tests); substudy-specific results were meta-analyzed. The pooled mean difference in annual rate of decline (MD) for vitamin D3 versus placebo was 0.01 (95% CI − 0.01, 0.02; p = 0.39). We observed no interaction with baseline 25-hydroxyvitamin-D levels (p-interaction = 0.84) and a significant interaction with self-reported race (p-interaction = 0.01). Among Black participants (19%), those assigned vitamin D3 versus placebo had better cognitive maintenance (MD = 0.04, 95% CI 0.01, 0.08, similar to that observed for Black participants 1.2 years apart in age). Thus, vitamin D3 (2000 IU/day cholecalciferol) supplementation was not associated with cognitive decline over 2–3 years among community-dwelling older participants but may provide modest cognitive benefits in older Black adults, although these results need confirmation.
Trial registration ClinicalTrials.gov; VITAL (NCT01169259), VITAL-DEP (NCT01696435) and VITAL-Cog (NCT01669915); the date the registration for the parent trial (NCT01169259) was submitted to the registry: 7/26/2010 and the date of first patient enrollment in either of the ancillary studies for cognitive function in a subset of eligible VITAL participants: 9/14/2011.

Full text

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Eect of vitamin D on cognitive
decline: results from two ancillary
studies of the VITAL randomized
trial
Jae H. Kang1*, Chirag M. Vyas2, Olivia I. Okereke1,2,3, Soshiro Ogata4, Michelle Albert5,
I.‑Min Lee3,6, Denise D’Agostino6, Julie E. Buring3,6, Nancy R. Cook3,6, Francine Grodstein1,7 &
JoAnn E. Manson3,6
Low vitamin D levels have been associated with cognitive decline; however, few randomized trials
have been conducted. In a trial, we evaluated vitamin D3 supplementation on cognitive decline.
We included participants aged 60+ years (mean[SD] = 70.9[5.8] years) free of cardiovascular
disease and cancer in two substudies in the VITAL 2 × 2 randomized trial of vitamin D3 (2000 IU/
day of cholecalciferol) and sh oil supplements: 3424 had cognitive assessments by phone (eight
neuropsychologic tests; 2.8 years follow‑up) and 794 had in‑person assessments (nine tests; 2.0 years
follow‑up). The primary, pre‑specied outcome was decline over two assessments in global composite
score (average z‑scores of all tests); substudy‑specic results were meta‑analyzed. The pooled mean
dierence in annual rate of decline (MD) for vitamin D3 versus placebo was 0.01 (95% CI − 0.01, 0.02;
p = 0.39). We observed no interaction with baseline 25‑hydroxyvitamin‑D levels (p‑interaction = 0.84)
and a signicant interaction with self‑reported race (p‑interaction = 0.01). Among Black participants
(19%), those assigned vitamin D3 versus placebo had better cognitive maintenance (MD = 0.04, 95%
CI 0.01, 0.08, similar to that observed for Black participants 1.2 years apart in age). Thus, vitamin
D3 (2000 IU/day cholecalciferol) supplementation was not associated with cognitive decline over
2–3 years among community‑dwelling older participants but may provide modest cognitive benets in
older Black adults, although these results need conrmation.
Trial registration ClinicalTrials.gov; VITAL (NCT01169259), VITAL‑DEP (NCT01696435) and VITAL‑
Cog (NCT01669915); the date the registration for the parent trial (NCT01169259) was submitted to
the registry: 7/26/2010 and the date of rst patient enrollment in either of the ancillary studies for
cognitive function in a subset of eligible VITAL participants: 9/14/2011.
Vitamin D is a fat-soluble steroid hormone essential for bone and muscle health. Yet, the discovery of vitamin
D’s autocrine pathways in multiple cell types has stimulated interest in its role in brain function1–14. Specically,
the vitamin D receptor is expressed in the cerebral cortex and hippocampus, critical for cognition and memory.
In animals, vitamin D deciency has been linked with decits in brain development and aging15–17.
In humans, observational studies have implicated low vitamin D in cognitive impairment and dementia18–20,
although the literature has been mixed21,22. Observational studies have used varying denitions of low vitamin
D and of cognitive impairment/dementia; further, the issue of reverse causation is important, as low vitamin D
concentrations may have resulted from lifestyle changes associated with incipient cognitive impairment/demen-
tia. ree major previous randomized clinical trials on cognitive change23–25 have not shown benets of vitamin
OPEN
1Channing Division of Network Medicine, Brigham and Women’s Hospital/Harvard Medical School, 181 Longwood
Ave, Boston, MA 02115, USA. 2Department of Psychiatry, Massachusetts General Hospital/Harvard Medical School,
Boston, MA, USA. 3Harvard T. H. Chan School of Public Health, Boston, MA, USA. 4Department of Preventive
Medicine and Epidemiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan. 5University of
California at San Francisco School of Medicine, San Francisco, CA, USA. 6Division of Preventive Medicine, Brigham
and Women’s Hospital/Harvard Medical School, Boston, MA 02215, USA. 7Rush Alzheimer’s Disease Center, Rush
University Medical Center, Chicago, IL, USA. *email: nhjhk@channing.harvard.edu
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D3. However, even a large trial (n = 4143) with 7.8years of follow-up that observed no eect of vitamin D3 and
calcium supplements on cognitive decline compared with placebo24 used a low dose of vitamin D3 (400IU/day).
us, we investigated whether vitamin D3 supplementation of 2000IU/day may delay cognitive decline over
2–3years compared to placebo among healthy participants aged 60+ years in VITAL (VITamin D and OmegA-3
TriaL; NCT01169259)26–28, a randomized trial of vitamin D3 and omega-3 fatty acids in the prevention of major
chronic diseases. In addition, we conducted pre-specied subgroup analyses by race and baseline blood vitamin
D levels, given that supplementation may have stronger eects on subgroups with relatively lower blood vitamin
D levels, including Black adults who are also at higher risk of cognitive decline29–31 and in whom we had observed
suggestively dierent eects of vitamin D supplementation in the parent VITAL trial32.
Results
e 3424 participants in VITAL-Cog were aged 60–91years (mean = 71.9; SD = 5.4) at the rst cognitive assess-
ment (Table1); 58.9% were women; 22.2% were Black participants and 49.8% had some years of post-graduate
studies. e mean change over an average of 2.8years of follow-up was − 0.25 (SD = 0.49) in those assigned to
placebo and − 0.24 (SD = 0.48) in those assigned to vitamin D. In CTSC-Cog (Table1), the 794 participants
were aged 60–87years (mean = 67.1; SD = 5.3) at the rst cognitive assessment; 50.4% were women; 5.7% were
Black participants and 55.5% had some post-graduate education. e mean change over a mean of 2.0years of
follow-up was 0.09 (SD = 0.39) in those assigned to placebo and 0.08 (SD = 0.40) in those assigned to vitamin D.
In VITAL-Cog, we did not observe an eect of vitamin D3 supplementation on cognitive function at the end
of follow-up (mean = 2.8years (range = 1.4–4.3years); Table2): the least squares mean for the global score was
− 0.28 standard units (SE = 0.01) for the vitamin D3 group and − 0.26 (SE = 0.02) for the placebo group (mean
dierence = − 0.02, 95% CI − 0.06, 0.02). We observed no multivariable-adjusted dierences in the global score
annual rate of decline by assignment (Table3; model 2, multivariable-adjusted mean dierence = 0.01, 95% CI
− 0.01, 0.02). Similarly, multivariable-adjusted dierences in annual rates of decline were not signicant for the
secondary outcomes: 0.01 (95% CI − 0.01, 0.03), verbal memory composite score; 0.01 (95% CI − 0.01, 0.02),
executive function/attention score and 0.03 (95% CI − 0.04, 0.09), TICS.
In CTSC-Cog (Table2), we did not observe an eect of vitamin D3 supplementation on cognition at the end of
follow-up (mean 2.0years (range = 1.0–3.1years)): the least squares mean for the global score was 0.11 (SE = 0.03)
for the vitamin D3 group and 0.06 (SE = 0.03) for the placebo group (mean dierence = 0.05, 95% CI − 0.04,
0.14). e multivariable-adjusted mean dierence in the global score annual rate of decline was − 0.004 (95% CI
− 0.04, 0.03; p = 0.83; Table3). Similarly, multivariable-adjusted mean dierences in annual rates of decline for
secondary cognitive systems were not signicant: 0.01 (95% CI − 0.05, 0.06) for the verbal memory composite
score; − 0.01 (95% CI − 0.05, 0.02) for the executive function/attention score and 0.04 (95% CI − 0.08, 0.17) for
the 3MS score (re-scaled to have range 0–41 points like the TICS). Results for individual tests are in TableS1.
We observed no heterogeneity in the results by substudy (p for heterogeneity ≥ 0.28); thus, the multivariable-
adjusted results were meta-analyzed (Table3). e pooled eect of vitamin D3 supplementation was a mean
dierence in the annual rate of decline of 0.01 (95% CI − 0.01, 0.02; p = 0.39) for the global score; 0.01 (95% CI
− 0.01, 0.02), verbal composite score; 0.01 (95% CI − 0.01, 0.02), executive function/attention composite score;
and 0.03 (95% CI − 0.03, 0.09), for general cognition (TICS/3MS).
For pre-specied interaction analysis (Table4) by race for the global composite score, we observed a signi-
cant interaction (pooled p-interaction = 0.01), where among Black participants, the vitamin D3 group showed
a signicantly slower rate of decline than placebo (pooled multivariable-adjusted mean dierence in annual
rate of decline = 0.04, 95% CI 0.01, 0.08), but not in other races (pooled multivariable-adjusted mean dier-
ence = − 0.001, 95% CI − 0.01, 0.01). To help interpret these results, among Black participants, at the 2nd assess-
ment in VITAL-Cog, those on vitamin D had a 0.03 standard units higher global score performance than those
on placebo; this dierence was equivalent to that observed with Black participants who were 1.2years apart in
age, indicating an overall modest eect. e benecial vitamin D3 eect among Black participants was stronger
for the executive function/attention score, where the eect was equivalent to the dierence observed between
Black participants who were 3.8years apart in age (when the more conservative xed eects summary was used
for estimation (Table5 footnote)). We observed no signicant interaction with the other pre-specied modi-
er of baseline blood 25(OH)D concentrations for the global score (pooled p-interaction = 0.84; Table4) or the
secondary outcomes (pooled p-interaction ≥ 0.12; Table5). Finally, we observed no signicant interactions for
the other 13 eect modiers evaluated for the global score (pooled p-interactions ≥ 0.18; Table4; for secondary
outcomes, see Table6).
In sensitivity analyses where we restricted the analyses in both substudies to those who reported no hearing
impairment (68% in VITAL-Cog; 86% in CTSC-Cog; pooled mean dierence in the annual rate of decline in
the global score was 0.01 (95% CI − 0.01, 0.02; p = 0.37)) or restricted the analyses to those enrolled from the 1st
assessment in VITAL-Cog (pooled mean dierence was 0.01 (95% CI − 0.01, 0.02; p = 0.39)) or restricted the
analyses in CTSC-Cog to those who did not have neuropsychiatric disorders or possible dementia at baseline
(72%; pooled mean dierence was 0.01 (95% CI − 0.01, 0.02; p = 0.40)) or restricted the analyses in both sub-
studies to those who were in the top 90% of performance in each outcome (to avoid oor eects and to remove
those with possible dementia, especially in VITAL-Cog; pooled mean dierence was − 0.001 (95% CI − 0.01,
0.01; p = 0.93)), results were similar to the main results. Results also did not dier when we additionally adjusted
for practice eects (pooled mean dierence was 0.01 (95% CI − 0.01, 0.02; p = 0.31)) or when we additionally
adjusted for season of cognitive assessment (pooled mean dierence was 0.01 (95% CI − 0.01, 0.02; p = 0.38)).
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Table 1. Baseline characteristics of participants aged 60+ years in the VITAL cognitive substudy by vitamin
D supplement assignment for VITAL-Cog (n = 3424) and CTSC-Cog (n = 794). 3MS Modied Mini-
Mental Status exam (range = 0–100)33; CTSC Clinical and Translational Science Collaborative Center for
VITAL in Boston, MA; EBMT East Boston Memory Test (range = 0–12)34; OTMT Oral Trail Making Test
(range = 0–120s)35,36; SD standard deviation; TICS Telephone Interview for Cognitive Status (range = 0–41)37;
TMT Trail Making Test (range = 0–150s for part A and range = 0–300s for part B)38,39. a Characteristics as
of randomization unless noted otherwise; for categorical variables, the percentages do not add to 100%
due to rounding errors and numbers do not add to the total due to missing values, which were taken out of
descriptive statistical analyses. In the VITAL-Cog, 501 completed only the baseline, 440 completed only the
2nd assessment and 2483 completed both assessments. In the CTSC-Cog, 497 completed both assessments,
279 completed only the baseline and 18 completed only the 2nd assessment. b“ Other race/ethnicity” includes
“Non-Black/African-American Hispanic”, “Asian”, “Native Hawaiian or other Pacic Islander” or “American
Indian/Alaska Native”. c Depression is dened as a lifetime history of a depression diagnosis or of treatment for
depression; current use of antidepressants; experiencing two or more weeks of depression in the past 2years or
scoring 10 points or higher on the Patient Health Questionnaire-8.
VITAL-Cog (n = 3424) CTSC-Cog (n = 794)
Vitamin D Group (n = 1710) Placebo Group (n = 1714) Vitamin D3 Group (n = 396) Placebo Group (n = 398)
Mean (SD)
Age at 1st interview, yearsa (n = 2984 in VITAL-Cog;
n = 776 in CTSC-Cog) 71.9 (5.4)
(n = 1480) 71.8 (5.4)
(n = 1504) 66.9 ± 5.2
(n = 385) 67.3 ± 5.4
(n = 391)
Age at 2nd interview, yearsa (n = 2923 in VITAL-Cog;
n = 515 in CTSC-Cog) 73.3 (5.7)
(n = 1466) 73.4 (5.7)
(n = 1457) 69.2 ± 5.1
(n = 254) 69.8 ± 5.6
(n = 261)
Cognitive test scores at 1st interview
VITAL-Cog only tests
TICS 33.9 (2.8) 34.0 (2.8) – –
OTMT-Part A (s) 10.7 (3.9) 10.3 (3.3) – –
OTMT-Part B (s) 38.0 (24.2) 37.9 (24.1) – –
Digit span backwards 6.7 (2.3) 6.8 (2.4) – –
CTSC-Cog only tests
3MS – – 94.8 ± 4.9 94.9 ± 4.4
TMT-Part A (s) – – 29.2 ± 11.5 29.8 ± 9.4
TMT-Part B (s) – – 80.0 ± 42.9 82.5 ± 44.2
Vegetable naming test – – 15.6 ± 4.6 15.4 ± 4.5
Common tests across VITAL-Cog and CTSC-Cog
TICS 10-word list recall-immediate 4.6 (1.7) 4.7 (1.7) 4.7 ± 1.3 4.7 ± 1.3
TICS 10-word list recall-delayed 2.7 (1.9) 2.7 (1.9) 2.0 ± 1.8 1.9 ± 1.7
EBMT-immediate 9.6 (1.7) 9.6 (1.8) 9.7 ± 1.7 9.7 ± 1.6
EBMT-delayed 9.3 (1.8) 9.3 (1.9) 9.3 ± 1.7 9.3 ± 1.7
Animal naming test 19.4 (5.5) 19.7 (5.6) 21.1 ± 5.9 20.3 ± 6.1
Global composite score − 0.02 (0.57) 0.02 (0.57) 0.02 (0.63) − 0.02 (0.56)
Baseline serum 25(OH)D (ng/mL) 32.2 (9.8) 32.5 (9.6) 28.0 (8.3) 29.1 (9.1)
n (%)
Omega-3 assignment
Active group 844 (49.4%) 855 (49.9%) 198 (50.0%) 198 (49.8%)
Placebo group 866 (50.6%) 859 (50.1%) 198 (50.0%) 200 (50.3%)
Sex
Female 1011 (59.1%) 1005 (58.6%) 205 (51.8%) 195 (49.0%)
Male 699 (40.9%) 709 (41.4%) 191 (48.2%) 203 (51.0%)
Self-reported race/ethnicity
Non-Hispanic White 1184 (71.3%) 1245 (73.8%) 341 (88.1%) 345 (89.2%)
Black 387 (23.3%) 356 (21.1%) 18 (4.7%) 26 (6.7%)
Other race/ethnicityb90 (5.4%) 85 (5.0%) 28 (7.2%) 16 (4.1%)
Highest attained education
High school or under 189 (11.1%) 183 (10.7%) 29 (7.3%) 34 (8.5%)
College 678 (39.7%) 664 (38.9%) 138 (34.9%) 152 (38.2%)
Post-graduate studies 842 (49.3%) 861 (50.4%) 228 (57.7%) 212 (53.3%)
Depressionc
No 1363 (82.7%) 1383 (82.9%) 324 (83.7%) 309 (79.8%)
Yes 285 (17.3%) 285 (17.1%) 63 (16.3%) 78 (20.2%)
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Discussion
In this randomized trial among generally healthy community-dwelling older participants followed for 2–3years,
supplementation with 2000IU/day of vitamin D3 was not associated with cognitive decline. No eects were
observed for the primary outcome as well as secondary outcomes of verbal memory, executive function/attention
and global cognition and for both substudies where cognition was assessed by phone or in person. However,
a pre-specied subgroup analysis showed cognitive benets over time for vitamin D3 supplementation versus
placebo among Black participants, but not by levels of 25(OH)D. Because the subgroup analyses by race may be
due to chance, the results should be interpreted with caution and conrmed in future studies.
Randomized trials of vitamin D and cognitive decline21,22,41 in relatively healthy populations have shown
conicting results, with most reporting no benet from supplementation, despite vitamin D’s potential neuropro-
tective anti-inammatory and antioxidant eects7–11,42. In the largest (n = 4143) and longest trial (7.8years dura-
tion) where women aged 65+ years received vitamin D3 (400IU/day) and calcium (1000mg/day) or placebo24,
Table 2. Cognitive function at two assessments by Vitamin D supplement assignment, for VITAL-Cog
participants aged 60 + years, (n = 3424) assessed by telephone and for CTSC-Cog participants aged 60 + years,
(n = 794) assessed in person. 3MS Modied Mini-Mental Status exam (range = 0–100)33; CI condence interval;
CTSC Clinical and Translational Science Collaborative center for VITAL in Boston, MA; TICS Telephone
Interview of Cognitive Status (range = 0–41)37. a In the VITAL-Cog, 2483 completed both assessments, 501
completed only the baseline, 440 completed only the 2nd assessment. In the CTSC-Cog, 497 completed both
assessments, 279 completed only the baseline and 17 completed only the 2nd assessment. b In the VITAL-
Cog: global score is a composite score representing the mean of the z-scores of 8 tests: TICS (range 0–41),
immediate and delayed recalls of the East Boston Memory Test, category uency (animal naming test), delayed
recall of the TICS 10-word list, oral trails making test A, oral trails making test B and digit span backwards.
Verbal memory score is a composite score representing the mean of the z-scores of 4 tests: the immediate and
delayed recalls of both the TICS 10-word list and the East Boston Memory Test. Executive function/attention
score is a composite score representing the mean of the z-scores of 4 tests: trails making test A and B, category
uency tests (naming animals), and digit-span backwards. In the CTSC-Cog: the global score is a composite
score representing the mean of the z-scores of 9 tests: 3MS, immediate and delayed recalls of the East Boston
Memory Test, category uency tests (naming animals and vegetables), the immediate and delayed recalls of
a 10-word list and trail-making tests A and B. Verbal memory score was dened the same way as in VITAL-
Cog. Executive function/attention score is a composite score representing the mean of the z-scores of 4 tests:
trails making tests A and B, category uency tests (naming animals and vegetables). c Least squares means
and standard errors and dierences of least squares means and standard errors were derived from univariate
models.
VITAL-COG (n = 3424; telephone assessments) CTSC-COG (n = 794; in-person assessments)
Vitamin D Group Placebo Group Dierence in score
at each timepoint
(Vitamin D
-Placebo; 95% CI)c
Vitamin D Group Placebo Group Dierence in
score at each
timepoint (Vitamin
D-Placebo; 95%
CI)c
N Mean (SE)cN Mean (SE)cN Mean (SE) N Mean (SE)
Primary outcome Primary outcome
Global composite
scorebDierence in scorecGlobal composite
scorebDierence in scorec
1st assessment
score 14,800 − 0.04 (0.01) 1504 − 0.01 (0.01) − 0.03 (− 0.07, 0.01) 1st assessment
scorec385 0.02 (0.03) 391 − 0.03 (0.03) 0.05 (− 0.04, 0.13)
2nd assessment
score 1466 − 0.28 (0.01) 1457 − 0.26 (0.02) − 0.02 (− 0.06, 0.02) 2nd assessment
scorec254 0.11 (0.03) 261 0.06 (0.03) 0.05 (− 0.04, 0.14)
Secondary outcomes Secondary outcomes
Verbal memory
composite scorebDierence in scorecVerbal memory
composite scorebDierence in scorec
1st assessment
score 14,800 − 0.02 (0.02) 1504 − 0.01 (0.02) − 0.01 (− 0.06, 0.04) 1st assessment
scorec385 0.01 (0.04) 391 − 0.02 (0.03) 0.03 (− 0.07, 0.13)
2nd assessment
score 1466 − 0.01 (0.02) 1457 − 0.02 (0.02) 0.01 (− 0.04, 0.07) 2nd assessment
scorec254 0.17 (0.04) 261 0.11 (0.04) 0.07 (− 0.05, 0.18)
Executive func-
tion/attention
compositeb scoreaDierence in scorecExecutive func-
tion/attention
compositeb scoreaDierence in scorec
1st assessment
score 14,800 − 0.05 (0.02) 1504 0.01 (0.02) − 0.05 (− 0.10,
− 0.01) 1st assessment
scorec385 0.03 (0.04) 391 − 0.05 (0.03) 0.08 (− 0.02, 0.18)
2nd assessment
score 1466 − 0.53 (0.02) 1457 − 0.49 (0.02) − 0.04 (− 0.08, 0.01) 2nd assessment
scorec254 0.04 (0.04) 261 − 0.03 (0.04) 0.06 (− 0.04, 0.16)
TICS Dierence in scorec3MS Dierence in scorec
1st assessment
score 14,800 33.81 (0.07) 1504 33.92 (0.07) − 0.12 (− 0.31, 0.08) 1st assessment
scorec385 94.80 (0.25) 391 94.86 (0.22) − 0.05 (− 0.71, 0.60)
2nd assessment
score 1466 33.92 (0.07) 1457 33.97 (0.07) − 0.05 (− 0.26, 0.16) 2nd assessment
scorec254 95.69 (0.23) 261 95.52 (0.24) 0.17 (− 0.48, 0.82)
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no association was observed between vitamin D3/calcium treatment and incident cognitive impairment or
dementia, although the vitamin D3 dose was low, and was one h of our dose. us, our ndings are important
in suggesting that even much higher doses of vitamin D3 do not provide meaningful cognitive benets overall.
Similarly, in two European randomized trials of 2000IU/day of vitamin D3 compared to placebo43 (n = 2157) or
800IU/day44 (n = 273) of vitamin D3 assessed over 343 and 244years among community-dwelling older persons
observed no dierences in change in cognitive function by intervention. Four small studies (n < 400)23,45–47 have
evaluated even higher doses of vitamin D3 but were short-term (≤ 1year of treatment) and also have not observed
signicant overall dierences in cognitive change. Among Black adults, in a 3-year study among 260 older women
(aged 65–73years) where higher doses of vitamin D3 (individualized doses of ≥ 2400IU/day needed to maintain
serum 25(OH)D ≥ 30ng/mL) and calcium (1200mg/day) was compared to placebo and calcium (1200mg/day),
Owusu etal.48 observed no dierence in change in MMSE performance, similar to our null nding for general
cognition for Black participants; change in executive function was not assessed in this study. us, our study
adds to the literature in that it was a long-term, large study (n > 4200) testing a relatively high dose of vitamin
D3 for long durations and had a relatively large representation of Black participants.
In subgroup analyses, we observed that in Black participants, vitamin D3 supplementation was signicantly
associated with better cognitive maintenance in the global score and executive function/attention score. is
is consistent with studies that have observed that vitamin D3 deciency is associated most prominently with
decits in executive function41,45,49. While the interaction by race and baseline blood 25(OH)D levels were pre-
specied, these subgroup ndings were not adjusted for multiple comparisons and thus, should be interpreted
with caution. We had hypothesized a priori that vitamin D3 might have particular benets in Black participants
who had lower 25(OH)D concentrations at baseline; yet, given the lack of a signicant eect modication by
Table 3. Meta-analysis of the mean dierences (95% CI) in change over time among VITAL-Cog participants
(n = 3424) and CTSC-Cog participants (n = 794), by Vitamin D supplement assignment. 3MS Modied
Mini-Mental Status exam (range = 0–100)33, CI condence interval; CTSC Clinical and Translational Science
Collaborative center for VITAL in Boston, MA; TICS Telephone Interview of Cognitive Status (range = 0–41)37.
a For denitions of the global scores and the key secondary outcomes for the two populations, see footnotes
for Table2. b From linear mixed models of cognitive performance: model 1 includes time since randomization
modelled as a continuous variable, vitamin D assignment, and their interaction. c From linear mixed models
of cognitive performance: model 2 is model 1 with adjustment for 6 additional variables, omega-3 assignment
(yes/no), sex (male/female), age at randomization (years), race/ethnicity (non-Hispanic white, black, other race/
ethnicity), education (high school or under, college, graduate school), history of depression (yes/no; see footnote
in Table1 for denition), and the six interaction terms (products with time since randomization). d Pooled
using Dersimonian and Laird xed-eects method for meta-analysis40 except for general cognition where the
p for heterogeneity across the two substudies was 0.04 and results were meta-analyzed with random-eects.
e Due to the dierences in scale between the TICS (0–41) used in VITAL-Cog and 3MS (range 0–100) used in
CTSC-Cog, for pooling purposes, the 3MS scores were multiplied by 0.41 for conversion to the same scale as the
TICS scores. As the p for heterogeneity across the two substudies was 0.04, the results were meta-analyzed with
Dersimonian and Laird method incorporating random-eects40. f None of the eects for the secondary outcomes
were signicant at Bonferroni-adjusted p-value of 0.0167 (= 0.05/3 secondary outcomes).
Difference in annual rate of change
Vitamin D – Placebo; 95% confidence interval)
Primary outcome: Global composite score*Model 1:
univariate†
Model 2:
multivariable-ad
j
usted‡
VITAL-Cog 0.01 (-0.01, 0.02) 0.01 (-0.01, 0.02)
CTSC-Cog 0.003 (-0.03, 0.04) -0.004 (-0.04, 0.03)
POOLED§0.01 (-0.01, 0.02)
pooled p-value=0.39
Key secondary outcomes
p
ooled p-values≥0.33¶
Verbal memory composite score*
VITAL-Cog 0.01 (-0.01, 0.03) 0.01 (-0.01, 0.03)
CTSC-Cog 0.02 (-0.04, 0.08) 0.01 (-0.05, 0.06)
POOLED§0.01 (-0.01, 0.02)
Executive function/attention composite score*
VITAL-Cog 0.01 (-0.01, 0.03) 0.01 (-0.01, 0.02)
CTSC-Cog -0.01 (-0.04, 0.03) -0.01 (-0.05, 0.02)
POOLED§0.01 (-0.01, 0.02)
General cognition||
VITAL-Cog 0.03 (-0.04, 0.10) 0.03 (-0.04, 0.09)
CTSC-Cog 0.04 (-0.08, 0.17) 0.04 (-0.08, 0.17)
POOLED§0.03 (-0.03, 0.09)
Placebo better Vitamin D better
-0. 2-0.10 0. 10.2
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Table 4. Mean dierence (95% CI) in rate of change in global score between vitamin D and placebo group:
eect modication by risk factors for cognitive decline. CI condence interval; CTSC-Cog, subset that received
in-person interviews at the Harvard Clinical and Translational Science Collaborative center for VITAL in
Boston, MA; CVD cardiovascular disease; VITAL-Cog subset that received telephone cognitive interviews in
VITAL. For denitions of the global scores for the two populations, see footnote for Table2. a Mean dierence
in annual rate of decline of vitamin D—placebo groups from multivariable-adjusted linear mixed models: see
footnotes for Table3. e stratied analyses were done among those with non-missing data on the eect modier.
b Interaction terms across the two substudies were pooled using Dersimonian and Laird xed-eects method for
meta-analysis. ere was signicant heterogeneity (p < 0.05) for two pooled p-interactions, and for these, random
eects were incorporated into the meta-analysis; the pooled p-for interaction was 0.48 for sex and 0.66 for
Vitamin D supplement use (< 800IU) outside of the trial. None of the interaction terms for the non-pre-specied
modiers were signicant at the Bonferroni-adjusted p-value of 0.0038 (= 0.05/13 subgroup analyses): pooled p
for interaction ≥ 0.18. c Stratum-specic estimates were pooled using Dersimonian and Laird xed-eects method
for meta-analysis. ere was signicant heterogeneity (p-het < 0.05) for three strata, and for these, random eects
were incorporated into the meta-analysis and presented in the Table. For reference, the xed eects meta-
analyzed pooled estimates were: 0.004 (95% CI − 0.01, 0.02) for females (p-het = 0.03), 0.003 (95% CI − 0.02, 0.02)
for those with multiple CVD risk factors (p-het = 0.04) and 0.01 (95% CI − 0.01, 0.02) for those using Vitamin D
supplements (< 800IU) outside of the trial (p-het = 0.03). d See footnote in Table1 for denition of depression.
e Median for the global score was 0.05 in both the VITAL-Cog and the CTSC-Cog. f Compliance is dened as
taking ≥ 2/3rd of pills on all of the follow-up questionnaires between the rst and the second cognitive assessment
and not initiating out-of-study sh oil supplementation.
DELOOPCSTCGOC-LATIV
C
haracteristics Difference (95%CI)†N Difference (95%CI)† N Difference (95%CI)†‡§
P
re-
s
pecified Modifie
r
s
‡10.0=noitcaretnirofpecardetroper-fleS
Non-Black 0.001 (-0.01, 0.01) 260
4
)10.0,10.0-(100.0-037)20.0,40.0-(10.0-
)80.0,10.0(40.044)04.0,10.0(02.0347)70.0,200.0-(40.0kcalB
‡48.0=noitcaretnirofpsleveldoolbD)HO(52enilesaB
)20.0,10.0-(200.0125)40.0,40.0-(100.0-7641)20.0,20.0-(300.0)Ld/gn23(naidem<
≥ )20.0,10.0-(10.0272)40.0,70.0-(20.0-7251)30.0,10.0-(10.0)Ld/gn23(naidem
N
on-pre-specified Modifiers‡
tnemssessatsriftaegA
)30.0,10.0-(10.0006)40.0,40.0-(200.01871)30.0,400.0-(10.0sraey07<
≥ )20.0,20.0-(200.0-491)30.0,01.0-(40.0-3461)20.0,20.0-(1000.0sraey07
tnemngissa3-agemO
)20.0,10.0-(10.0893)30.0,70.0-(20.0-5271)30.0,10.0-(10.0oN
)20.0,10.0-(300.0693)60.0,40.0-(10.09961)20.0,20.0-(200.0seY
§‡xeS
Female 0.01 (-0.01, 0.03) 201
6
)40.0,70.0-(20.0-004)100.0,01.0-(50.0-
)20.0,10.0-(10.0493)70.0,10.0-(30.08041)20.0,20.0-(200.0elaM
noitacudE
High School/College -0.003 (-0.02, 0.02) 171
4
)20.0,20.0-(200.0-353)60.0,40.0-(10.0
)30.0,10.0-(10.0044)30.0,60.0-(10.0-3071)30.0,200.0-(20.0seidutsegelloc-tsoP
||noisserpeD
N
o 0.01 ( -0.01, 0.02) 274
6
)20.0,10.0-(10.0336)40.0,30.0-(200.0
Ye s 0.01 (-0.02, 0.04) 57
0
)40.0,20.0-(10.0141)11.0,01.0-(100.0
Body mass index (kg/m2)
)10.0,30.0-(10.0-832)40.0,90.0-(20.0-7011)20.0,30.0-(10.0-52<
)40.0,400.0(20.0533)70.0,30.0-(20.03231)40.0,300.0(20.092-52
≥ )20.0,30.0-(10.0-122)30.0,90.0-(30.0-909)30.0,30.0-(3000.0-03
setebaiD
No 0.01 (-0.01, 0.02) 2955 -0.0002 (-0.03, 0.03)711 0.004 (-0.01, 0.02)
)50.0,20.0-(10.028)70.0,51.0-(40.0-564)60.0,20.0-(20.0seY
noisnetrepyH
N
)20.0,10.0-(10.0914)40.0,50.0-(300.0-7551)20.0,10.0-(10.0o
Ye s 0.01 (-0.01, 0.02) 1852 )20.0,10.0-(300.0173)30.0,70.0-(20.0-
loretselohchgiH
)20.0,10.0-(10.0764)60.0,20.0-(20.09491)20.0,10.0-(10.0oN
)20.0,20.0-(200.0423)10.0,01.0-(40.0-5441)30.0,10.0-(10.0seY
Multiple CVD risk factors§
<2 risk factors 0.004 (-0.01, 0.02) 183
6
)20.0,10.0-(10.0574)50.0,30.0-(10.0
≥2 risk factors 0.01 (-0.01, 0.03) 141
4
)50.0,80.0-(20.0-603)300.0,11.0-(50.0-
§‡esutnemelppus3DnimatiV
)20.0,20.0-(200.0604)80.0,20.0-(30.03171)20.0,20.0-(200.0-oN
)40.0,60.0-(10.0-883)10.0,80.0-(40.0-1171)30.0,200.0-(20.0)UI008<(seY
Baseline global score
¶
≤median of baseline score 0.01 (-0.01, 0.03) 1492 )30.0,10.0-(10.0883)60.0,40.0-(10.0
>median of baseline score -0.0001 (-0.02, 0.02) 1492 )10.0,20.0-(200.0-883)20.0,60.0-(20.0-
Compliance to treatment*
*
Compliant 0.01 (-0.01, 0.02) 295
4
)20.0,10.0-(10.0557)30.0,40.0-(400.0-
)50.0,30.0-(10.092)03.0,61.0-(70.0704)50.0,30.0-(10.0tnailpmoc-noN
Placebo better Vitamin D better
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baseline blood 25(OH)D levels in this substudy and the main trial28, the reasons for the specic benets in Black
participants remain unclear. A future evaluation using novel biomarkers of vitamin D (e.g., vitamin D binding
protein (VDBP) or free 25(OH)D)29,30,50,51 and genetic variants for VDBP52–54 that show dierence in distribution
across race/ethnicity groups may be insightful. Also, it is notable that Black participants had a higher prevalence
of diabetes and other cardiovascular risk factors, and lower baseline blood 25(OH)D levels, education and base-
line cognitive scores, which were characteristics of subgroups for which vitamin D had a suggestively stronger
Table 5. Pooled results across VITAL-Cog and CTSC-Cog for mean dierence in annual rate for the secondary
outcomes for vitamin D-Placebo: eect modication by race and blood 25(OH)D levels for cognitive decline.
3MS Modied Mini-Mental Status exam (range = 0–100)33; CI condence interval; CTSC Clinical and
Translational Science Collaborative center for VITAL in Boston, MA; TICS Telephone Interview of Cognitive
Status (range = 0–41)37. For denitions of the secondary outcomes for the two populations, see footnotes for
Table2. a From multivariable-adjusted linear mixed models of cognitive performance (model 2) as described
in footnote in Table3. b Pooled using Dersimonian and Laird xed-eects method for meta-analysis40 unless
otherwise noted. c Pooled using Dersimonian and Laird random-eects method for meta-analysis40 as the p for
heterogeneity was 0.001; if xed eects methods are used, the pooled estimate was 0.07 (95% CI 0.03, 0.12).
d Not signicant at Bonferroni-corrected p-value of 0.0167 (= 0.05/3 outcomes). e Due to the dierences in scale
between the TICS (0–41) used in VITAL-Cog and 3MS (range 0–100) used in CTSC-Cog, for pooling purposes,
the 3MS scores were multiplied by 0.41 for conversion to the same scale as the TICS scores.
Multivariable-adjusted difference in annual rate of change (Vitamin D – Placebo; 95% CI)†
SELF-REPORTED RACE BASELINE 25(OH)D BLOOD LEVELS
P
OOLED p-interactions|| p-interactions ≥0.20p-interactions≥0.12
Verbal memory composite scor
e
Non-Blac
k
< median (32 ng/dL)
V
ITAL-Cog 0.001 (-0.02, 0.02) -0.01 (-0.04, 0.02)
C
TSC-Cog 0.01 (-0.06, 0.07)0.01 (-0.06, 0.09)
P
OOLED
‡
0.002 (-0.02, 0.02) -0.01 (-0.03, 0.02)
Blac
k
≥ median (32 ng/dL)
V
ITAL-Cog 0.01 (-0.04, 0.06)0.03 (-0.002, 0.05)
C
TSC-Cog 0.10 (-0.17, 0.36) -0.02 (-0.12, 0.08)
P
OOLED
‡
0.01 (-0.04, 0.07)0.02 (-0.004, 0.05)
E
xecutive function/attention composite score
Non-Blac
k
< median (32 ng/dL)
V
ITAL-Cog 0.004 (-0.01, 0.02) 0.02 (-0.01, 0.04)
C
TSC-Cog -0.03 (-0.06, 0.01) -0.01 (-0.05, 0.04)
P
OOLED
‡
-0.002 (-0.02, 0.01) 0.01 (-0.01, 0.03)
Blac
k
≥ median (32 ng/dL)
V
ITAL-Cog 0.06 (0.02, 0.10) -0.0004 (-0.02, 0.02)
C
TSC-Cog 0.40 (0.20, 0.59) -0.03 (-0.09, 0.03)
P
OOLED
‡
0.21 (-0.12, 0.54)
§
-0.01 (-0.03, 0.02)
General cognitio
n
¶
Non-Blac
k
< median (32 ng/dL)
V
ITAL-Cog 0.02 (-0.06, 0.09) -0.02 (-0.12, 0.09)
C
TSC-Cog 0.05 (-0.08, 0.18)0.01 (-0.15, 0.16)
P
OOLED
‡
0.02 (-0.04, 0.09) -0.01 (-0.09, 0.08)
Blac
k
≥ median (32 ng/dL)
V
ITAL-Cog 0.06 (-0.15, 0.26)0.09 (-0.02, 0.19)
C
TSC-Cog 0.02 (-0.65, 0.69)0.09 (-0.14, 0.31)
P
OOLED
‡
0.05 (-0.14, 0.25)0.09 (-0.01, 0.18)
-0.7 00.7 -0.7 00.7
Placebo better Vitamin D better Placebo better Vitamin D better
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Table 6. Pooled results across VITAL-Cog and CTSC-Cog for mean dierence in annual rate for the secondary
outcomes for vitamin D-Placebo: eect modication by risk factors for cognitive decline. 3MS Modied Mini-
Mental Status exam; CI condence interval; CTSC-Cog subset that received in-person interviews at the Harvard
Clinical and Translational Science Collaborative center for VITAL in Boston, MA; TICS Telephone Interview of
Cognitive Status; VITAL-Cog subset that received telephone interviews in VITAL. From multivariable-adjusted
linear mixed models of cognitive performance (model 2) as described in footnote in Table3. a For denitions
of the verbal memory and executive function scores for the two populations, see footnotes for Table2. For
general cognition, due to the dierences in scale between the TICS (0–41) and 3MS (range 0–100), for
pooling purposes, the 3MS scores were multiplied by 0.41 for conversion to the same scale as the TICS scores.
b Interaction terms across the two substudies were pooled using Dersimonian and Laird xed-eects method for
meta-analysis. For a few interactions where there was signicant heterogeneity (p < 0.05) for the estimate across
the two substudies, random eects were incorporated into the meta-analysis. Among these non-pre-specied
modiers for secondary outcomes, none of the pooled p-interactions were signicant at Bonferroni-adjusted
p-value of 0.0038 (= 0.05/13 subgroup analyses), except for three nominally signicant pooled p-interactions
for education for verbal memory (p = 0.04), diabetes for executive function/attention (p = 0.04); compliance
for general cognition (p = 0.01). c Stratum-specic estimates were pooled using Dersimonian and Laird xed-
eects method for meta-analysis. For a few strata where there was signicant heterogeneity (p < 0.05) for the
estimate across the two substudies, random eects were incorporated into the meta-analysis. For reference, the
xed eects pooled estimate for executive function/attention is 0.002 (95% CI − 0.02, 0.02) for those without
hypertension; 0.01 (95% CI − 0.01, 0.03) for those taking Vitamin D supplements (< 800IU) outside of the trial;
and the pooled estimate for general cognition is − 0.001 (95% CI − 0.08, 0.08) for those without hypertension
and 0.03 (95% CI − 0.06, 0.13) for those with multiple CVD risk factors. d For the denition of depression, see
footnote in Table1. e For the verbal memory score, the median was -0.02 standard units in VITAL-Cog and 0.02
in the CTSC-Cog; for the executive memory/attention score, the median was 0.04 in VITAL-Cog and 0.02 in
the CTSC-Cog; for TICS, the median was 34 in VITAL-Cog and for the 3MS in CTSC-Cog, the median was
96 (equivalent to 39 on the transformed variable to have the same range as the TICS). f Compliance is dened
as taking ≥ 2/3rd of pills on all of the follow-up questionnaires between the rst and the second cognitive
assessment and not initiating out-of-study sh oil supplementation.
VERBAL MEMORY†
EXECUTIVE
FUNCTION/ATTENTION†GENERAL COGNITION†
Char
acteristics
‡§
Difference (95%CI)Difference (95%CI)Difference (95%CI)
Age at first assess
ment
)11.0,40.0-(40.0)30.0,10.0-(10.0)40.0,10.0-(20.0sraey07<
≥ )31.0,60.0-(30.0)30.0,20.0-(300.0)20.0,30.0-(10.0-sraey07
Om
ega-3 assignment
)11.0,50.0-(30.0)20.0,20.0-(300.0)40.0,10.0-(20.0oN
)11.0,70.0-(20.0)30.0,10.0-(10.0)20.0,30.0-(300.0-seY
Sex
)11.0,60.0-(30.0)30.0,10.0-(10.0)30.0,20.0-(100.0elameF
)31.0,40.0-(40.0)20.0,20.0-(200.0-)40.0,10.0-(10.0elaM
Education
College/High School -0.01 (-0.04, 0.01)0.01 (-0.01, 0.03)-0.002 (-0.09, 0.09)
Post-graduate studies 0.03 ( 0.001, 0.05) -0.0003 (-0.02, 0.02
)0
.06 (-0.02, 0.14)
Depr
ession
||
)31.0,200.0(70.0)20.0,10.0-(10.0)30.0,10.0-(10.0oN
)60.0,72.0-(11.0-)40.0,30.0-(10.0)60.0,40.0-(10.0seY
Body ma
ss index (kg/m
2
)
)90.0,31.0-(20.0-)10.0,40.0-(20.0-)40.0,20.0-(10.052<
)12.0,30.0(21.0)50.0,10.0(30.0)40.0,20.0-(10.092-52
≥ )50.0,81.0-(70.0-)30.0,30.0-(100.0)30.0,50.0-(10.0-03
Diabetes
)01.0,30.0-(40.0)20.0,10.0-(2000.0)30.0,10.0-(10.0oN
)51.0,02.0-(20.0-)01.0,200.0(50.0)30.0,70.0-(20.0-seY
Hypertension
)22.0,51.0-(30.0)50.0,80.0-(20.0-)30.0,20.0-(10.0oN
)41.0,40.0-(50.0)30.0,10.0-(10.0)30.0,20.0-(10.0seY
High cholesterol
N
)11.0,50.0-(30.0)20.0,20.0-(300.0-)50.0,300.0-(20.0o
)31.0,60.0-(30.0)40.0,10.0-(20.0)20.0,40.0-(10.0-seY
Multiple
CVD risk factors
)01.0,50.0-(30.0)10.0,20.0-(400.0-)40.0,10.0-(20.0srotcafksir2<
≥ )22.0,62.0-(20.0-)40.0,10.0-(10.0)20.0,30.0-(10.0-srotcafksir2
V
itamin D supplement use
)60.0,21.0-(30.0-)20.0,20.0-(10.0)30.0,20.0-(400.0oN
)71.0,10.0(90.0)50.0,70.0-(10.0-)30.0,20.0-(10.0)UI008<(seY
Baselin
e score
¶
≤median of baseline scor
e
0.01 (-0.02, 0.04)0.01 (-0.02, 0.03
)0
.04 (-0.05, 0.12)
>median of baseline scor
e
0.01 (-0.01, 0.03)-0.01 (-0.03, 0.01)0.01 (-0.06, 0.08)
Co
mpliance to treatment**
)21.0,10.0-(60.0)20.0,10.0-(200.0)30.0,10.0-(10.0tnailpmoC
)10.0,93.0-(91.0-)01.0,10.0-(50.0)30.0,80.0-(20.0-tnailpmoc-noN
Placebo better Vitamin D better Placebo better Vitamin D better Placebo better Vitamin D bet
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benecial eect, particularly for executive function; thus, the concentration of a multitude of risk factors for
cognitive decline may have led to stronger benets of vitamin D in Black participants.
Limitations of our study warrant consideration. First, in VITAL-Cog, cognitive assessments were conducted
over the phone; however, our validation of the telephone cognitive assessment with in-person assessment showed
reasonable validity, and the main results were similar in CTSC-Cog, with in-person cognitive assessments.
While telephone interviews increased participation, it is possible that there was more misclassication in out-
come assessment and that subtle changes were missed compared to in-person assessments. Our trial included
mostly healthy, well-educated individuals (> 50% had post-graduate studies); this likely led to modest observed
cognitive decline and few participants being vitamin D decient. Both factors may have limited our ability to
detect modest eects of vitamin D3 supplements on cognition. Also, while a dose of 2000IU/day was used in
the study, it is possible that the optimal dose for brain health might be higher, although the literature has been
inconsistent43,48,55. Finally, the follow-up period of 2–3years, with only two assessments, may have been too short
to detect eects of vitamin D3 supplementation, particularly in a healthy population at relatively lower risk for
cognitive decline. Although in VITAL-Cog, we did observe cognitive decline in the placebo group over 2.8years
follow-up, additional studies with longer durations of follow-up and more cognitive assessments among those
at highest risk of vitamin D deciency and cognitive decline would be important.
Our study had several strengths. is was a randomized trial including > 4200 participants, with high rates of
follow-up and adherence to the assigned treatment group. In particular, there was a relatively high proportion of
Black participants (19%), who are at high risk for vitamin D insuciency30,56–58. Also, we were able to investigate
the eect of vitamin D3 supplements on multiple cognitive domains.
In conclusion, among generally well-educated healthy adults aged 60+ years, supplementation of vitamin
D3 (2000IU/day) did not slow cognitive decline over 2–3years, although there were modest benets observed
specically in Black older adults that should be conrmed in future studies.
Methods
Study design, randomization and masking, and procedures. VITAL trial. VITAL26–28 is a com-
pleted large randomized, double-blind, placebo-controlled, 2 × 2 factorial clinical trial of vitamin D3 (vitamin
D3[cholecalciferol], 2000IU/day) and marine omega-3 fatty acid (Omacor® sh oil, eicosapentaenoic acid + do-
cosahexaenoic acid, 1g/day) oral supplements in the primary prevention of cancer and cardiovascular dis-
ease. Participants were free of cancer (except non-melanoma skin cancer) and cardiovascular disease. Partici-
pants (n = 25,871 US men aged ≥ 50 and women aged ≥ 55 years) were randomized from 2011 to 2014 and
were required to limit using out-of-study supplemental vitamin D3 to ≤ 800IU/day, supplemental calcium to
≤ 1200mg/day, and to avoid using omega-3 fatty acid supplements. Supplementation with 2000IU/day vitamin
D3 for one year in VITAL led to a 40% mean increase in 25-hydroxyvitamin D (25(OH)D) levels (from 29.8
to 41.8ng/mL)28. e VITAL trial main phase has been completed, and its trial design (including details on
randomization and masking)26 and main ndings have been published27,28. e marine n-3 arm results for the
cognitive substudies have been analyzed separately59.
Participants. We used data from two distinct subsets of VITAL participants. Although cognitive function
was not the main planned outcome to be evaluated in the parent VITAL trial, assessing cognitive function was
planned before the start of the trial and baseline cognitive function assessments were planned to occur before
randomization as much as possible. One subset (VITAL-Cog; NCT01669915); n = 3424) completed cognitive
assessments by phone with randomization and again 2.8years later. Another subset (CTSC-Cog; n = 794 in an
ancillary study of depression (VITAL-DEP; NCT01696435)) completed in-person cognitive assessments with
randomization and again 2.0years later.
In VITAL-Cog, the baseline cognitive interview was conducted from September 2011 through April 2014
(mean = 1month before randomization; range of 1.2years before to 0.5years aer randomization (1.31% done
> 1month aer randomization); Fig.1a). Of 3658 eligible people as of April 2014 and we attempted to contact,
241 (7%) were unreachable, and of 3417 contacted, 3271 (96%) participated. We further excluded 262 participants
who were also in the CTSC-Cog, leaving 3009 participants (2984, including 317 Black participants, with complete
scores on all tests and 25 with scores missing on some tests). For the 2nd cognitive assessment (February 2013 to
June 2016), of the 3009 who participated in the 1st assessment, 58 died (2%) and 322 were unreachable (11%).
Of the 2629 contacted, 100 (4%) refused, and 2529 (96%) participated (2501 with complete scores on all tests
and 28 with scores missing on some tests).
To allow for enough time for follow-up assessments within the trial period and because we had reached the
target of 3000 participants, we stopped administering baseline cognitive assessments in April 2014, even though
there were additional eligible participants. However, to increase the number of Black participants, at the initiation
of 2nd assessments, we invited 618 additional eligible Black participants (Fig.1a: aged 60+ years at randomiza-
tion and willing to be part of VITAL-Cog). Of 618 Black participants, 141 (23%) could not be contacted. Of
477 contacted, 48 refused (10%) and 429 (90%) participated (November 2014 to June 2016; 422 with complete
scores on all tests; and 7 with scores missing on some tests). us, the total number of unique individuals in
VITAL-Cog was 3424: 2984 with complete baseline assessments and 2923 (= 2501 + 422 new Black participants)
with complete follow-up assessments.
In CTSC-Cog, the baseline assessment occurred from January 2012 to March 2014 (mean = 0.5month before
randomization; range of 3.0months before to within 1month aer randomization). For CTSC-Cog (Fig.1b),
we excluded 229 participants aged < 60years and four people who refused participation, leaving 821 partici-
pants (776 with complete scores on all tests and 45 with scores missing on some tests). A 2-year follow-up in-
person interview was conducted from January 2014 through April 2016. Of 821 who participated in the baseline
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assessment, 3 died (0.4%), 217 (26%) were ineligible for VITAL-DEP due to their baseline assessments showing
neuropsychiatric disorders, 6 (1%) showed neuropsychiatric disorders and possible dementia, 55 (7%) refused;
and 540 participated (515 with complete scores on all tests and 25 with scores missing on some tests). e total
number of unique individuals in CTSC-Cog was 794 (including 44 Black participants): 776 with complete base-
line assessments and 515 with complete follow-up assessments.
Standard protocol approvals, registrations, and patient consents. e research followed the Dec-
laration of Helsinki, and this substudy protocol was approved by the institutional review board of the Brigham
and Women’s Hospital. Written informed consent was obtained directly from VITAL participants and CTSC-
Cog participants or from their legally authorized representatives/next of kin26; for VITAL-Cog, completion of
cognitive tests was considered as implied consent.
Figure1. (a) Flow of Participants in the VITAL-Cog Ancillary Study to the VITAL Trial. (b) Flow of
Participants in the subset of CTSC-Cog participants in the VITAL-DEP Ancillary Study to the VITAL Trial.
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Participants and outcomes: VITAL‑Cog study population and telephone cognitive function
assessments. In VITAL-Cog substudy, the eligibility criteria were age 60+ years and in the screening ques-
tionnaire, being willing to participate in cognitive function assessments. Cognition was assessed by telephone
by trained interviewers, with eight neuropsychological tests assessing general cognition (Telephone Interview
of Cognitive status (TICS; range = 0–41 points)), verbal memory, and executive function/attention (see details
in the “Supplementary Methods”). We derived a global composite score by averaging the z-scores of the eight
individual tests (based on the baseline test distributions). When generating composite scores for the 2nd assess-
ment, the baseline means and SDs of scores from VITAL-Cog were used. Our primary, pre-specied outcome
was the annual rate of change of the global composite score, and for secondary outcomes, we also evaluated the
TICS and composite scores for verbal memory and executive function/attention (“Supplementary Methods”).
Participants and outcomes: CTSC‑Cog study population and in‑person cognitive function
assessments. A subgroup of 1054 VITAL participants received in-person health assessments, including
cognitive assessments as part of VITAL-DEP60, by trained interviewers at the CTSC in Boston with randomi-
zation (CTSC-Cog). e in-person cognitive battery included nine cognitive tests assessing general cognition
(Modied Mini-Mental State (3MS; range = 0–100)33), verbal memory and executive function/attention. e
CTSC global composite score, the primary outcome, was calculated as the average of the z-scores for the nine
assessments, using the CTSC-Cog baseline means and SDs, for both baseline and follow-up; secondary out-
comes included the 3MS and verbal memory and executive function/attention composite scores (“Supplemen-
tary Methods”).
Validation study of the VITAL‑Cog telephone cognitive assessment. Cognitive assessment by
phone has been extensively validated61,62. In VITAL-Cog, we validated our telephone cognitive assessment
against in-person assessments among a subset of 181 of the 262 CTSC participants with both assessments who
had the two within 1month of each other. We compared the global composite score derived from scores on the
eight tests administered by telephone versus a similar score derived from the nine tests administered in-person.
e intraclass correlation between the two modes was 0.64, supporting the validity of our telephone cognitive
interview (“Supplementary Methods”).
Statistical analyses. We compared characteristics at randomization by treatment group using Wilcoxon’s
rank-sum tests for continuous variables and chi-square tests for proportions. Primary analyses were conducted
using the intention to treat principle. For each substudy, linear mixed-eects models with random intercepts
were used to estimate the mean change in participants’ scores as a function of time (years between randomiza-
tion and each assessment), treatment assignment, and their interaction63. We tted models by maximum likeli-
hood, incorporating the longitudinal correlation within participants (using unstructured covariance structure);
for statistical testing, we used Wald tests. We calculated multivariable-adjusted mean dierences in annual rate
of decline and 95% condence intervals (CIs); information on covariates at pre-randomization were collected by
questionnaires. We used two models: model 1 included just the treatment group, while model 2 was additionally
adjusted for age at randomization (years), sex, highest attained education, race, omega-3 treatment arm assign-
ment, and depression history.
In secondary analyses, we evaluated potential eect modication by race and baseline blood vitamin D levels,
which were pre-specied given that supplementation may have stronger eects on subgroups with relatively lower
blood vitamin D levels such as Black participants29,30. We also evaluated eect modication by testing the 3-way
interaction terms in multivariable-adjusted linear mixed models for 13 possible risk factors of cognitive decline
(based on self-report on pre-randomization questionnaires): age, sex, omega-3 fatty acid assignment, education,
depression, body mass index, diabetes, hypertension, high cholesterol, multiple CVD risk factors, out-of-study
vitamin D3 supplement use, baseline score and compliance (over the entire follow-up period).
For the primary outcome of global score and for the two pre-specied subgroup analyses, the signicance tests
were 2-sided, and the signicance level was p-value < 0.05. For the secondary outcomes and subgroup analyses,
multiple comparisons were adjusted using Bonferroni corrections.
We rst evaluated associations separately by substudy and then pooled the substudy-specic results using
the Dersimonian and Laird meta-analytic approach incorporating xed-eects40. Because the TICS and 3MS
had dierent scales, for pooling, we multiplied the 3MS scores by 0.41 to generate the same scale as the TICS.
In sensitivity analyses, we restricted the analyses in both substudies to those who reported no hearing impair-
ment (68% in VITAL-Cog; 86% in CTSC-Cog), restricted the analyses to those enrolled from the 1st assessment
in VITAL-Cog (to ascertain whether missingness in the data can be assumed to be missing at random), restricted
the analyses in CTSC-Cog to those who did not have neuropsychiatric disorders or possible dementia at baseline
(72%), and restricted the analyses in both substudies to those who were in the top 90% of performance in each
outcome. In additional analyses, we additionally adjusted for practice eects by adjusting for the number of prior
assessments and in alternate models, we additionally adjusted for the season of cognitive assessment as vitamin
D levels may depend on season of the year.
For statistical analyses, we used SAS (SAS release 9.4; SAS Institute Inc, Cary, NC). For the cognitive ancillary
substudies, there was no data monitoring committee. is study is registered with ClinicalTrials.gov VITAL-Cog
(NCT01669915), VITAL-DEP (NCT01696435) and VITAL (NCT01169259).
Data availability
e corresponding author can be contacted for de-identied data requests. Analysis proposal requests will require
review and approval by the VITAL Publications & Presentations Committee and appropriate IRB approval. Once
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approved and a data access agreement has been executed, deidentied data generated from this research will be
made available to aliated investigators through secure databases for the prespecied analysis.
Received: 1 August 2021; Accepted: 1 November 2021
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Acknowledgements
VITAL (NCT01169259), VITAL-DEP (NCT01696435) and VITAL-Cog (NCT01669915) are registered with
ClinicalTrials.gov. VITAL-Cog was supported by R01 AG036755; VITAL-DEP was supported by R01 MH091448;
and VITAL was supported by Grants U01 CA138962, R01 CA138962, and UL1TR001102 including support from
the National Cancer Institute, National Heart, Lung and Blood Institute, Oce of Dietary Supplements, National
Institute of Neurological Disorders and Stroke, and the National Centre for Complementary and Integrative
Health. e ancillary studies are supported by grants from multiple Institutes, including the National Heart,
Lung and Blood Institute; the National Institute of Diabetes and Digestive and Kidney Diseases; the National
Institute on Aging; the National Institute of Arthritis and Musculoskeletal and Skin Diseases; the National Insti-
tute of Mental Health; and others. e funding sources had no role in the study design; the collection, analysis,
and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.
Author contributions
J.H.K., O.I.O., F.G., J.E.M. conceptualized the study design, investigation; J.H.K., O.I.O., D.D., F.G., J.E.M. curated
the data and provided project administration; J.H.K., N.R.C. and C.M.V. did the formal analysis; J.H.K., O.I.O.,
F.G., J.E.M. acquired the funding; J.H.K., O.I.O., C.M.V., S.O., J.E.M. wrote the original dra; J.H.K. and C.V.M.
accessed and veried the data, and all authors (J.H.K., C.M.V., O.I.O., S.O., M.A., I.L., D.D., J.E.B., N.R.C., F.G.,
J.E.M.) provided input on the interpretation of the data, reviewed and edited the nal submitted dra of the
manuscript.
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Competing interests
e authors declare no competing interests.
Additional information
Supplementary Information e online version contains supplementary material available at https:// doi. org/
10. 1038/ s41598- 021- 02485-8.
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