Supplemental Digital Content 1 for Psychosomatic Medicine
Online Supplemental Material
(1) Detailed description of primary and ancillary measures
(2) Testing inflammation as a potential mediator
(3) Table S1: Baseline sample characteristics for the primary study variables
(4) Table S2. Significance test and effect sizes for the loneliness by supplementation group
interaction predicting cognitive function scores
(5) Table S3. Significance test for the main effect of supplementation group predicting
cognitive function scores
(6) Table S4: Planned contrasts examining the effect of supplementation for people who
were more or less lonely
(7) Table S5: Residual change in cognitive function scores from pre to post supplementation.
(8) References for online supplemental material
Supplemental Digital Content 1 for Psychosomatic Medicine
Detailed Description of Primary and Ancillary Measures
The California Verbal Learning Test, Second Edition (CVLT-II) is a well-established
measure of verbal episodic memory [1,2]. Indices of immediate free recall, short-delay free
recall, and long-delay free recall measured verbal episodic memory. Across 5 different trials,
participants heard a list of the same 16 words and were immediately asked to recall the entire list.
The total number of words recalled across the learning trials served as a measure of immediate
free recall. After hearing a separate word list, participants were asked to recall words from the
original list, assessing short-delay free recall (which could be affected by retroactive interference
from the second list). Participants were also asked to remember words from the original list after
a 20-minute delay, assessing long-delay free recall. Alternate versions of the test were
administered at each visit to minimize practice effects, and the order of the test versions was
determined randomly. Scoring was completed using CVLT-II Comprehensive Scoring System
software, with higher numbers indicating better verbal episodic memory [1].
Three tests from the Wechsler Memory Scale – Third Edition (WMS-III) assessed
working memory [3]. The Digit Span and Letter-Number Sequencing tasks measured verbal
working memory whereas the Spatial Span task measured visuospatial working memory. To
complete the digit span task, participants were given an increasingly long list of numbers and
were asked to recall them either forward or backwards. The Letter-Number Sequencing test
consisted on a list of mixed letters and numbers; participants were asked to recall both in
ascending order. For the Spatial Span task, participants watched an experimenter touch a series
of blocks with different numbers on them and were asked to repeat the same sequence. All three
tasks were scored according to standard WMS-III instructions, with higher numbers reflecting
better working memory [3].
Supplemental Digital Content 1 for Psychosomatic Medicine
The Trail Making task was used to measure executive function [4]. Participants were
given a sheet with numbers dispersed on the page and were asked to connect the numbers in
numeric order (Part A). Next they were given a sheet with numbers and letters on the page and
were asked to connect both in ascending order, alternating between letters and numbers (Part B).
To obtain a clean measure of executive function, the time participants took (in seconds) to
complete Part A was subtracted from Part B [4]. Higher numbers correspond to better executive
function.
The Controlled Oral Word Association Task test assessed verbal fluency and processing
speed [5]. Participants were given a time limit to generate as many words as possible that started
with a certain letter. The total number of words participants generated across three letter trials
was used to compute processing speed; higher numbers reflect better verbal fluency and
processing speed.
The Center for Epidemiological Studies Depression (CES-D) Scale is one of the most
commonly used measures of depressive symptoms [6]. The CES-D has good discriminant
validity, construct validity, and test-retest reliability. The CES-D was included to account for
potential relationships among depression, loneliness, and cognitive function [7–9].
The Pittsburgh Sleep Quality Index measured sleep quality over the past month (PSQI)
[10]. The PSQI can distinguish between people with and without sleep disturbances, indicating
acceptable discriminant validity. The PSQI provided a way to disentangle sleep quality from the
link between loneliness and cognitive function [11,12].
Activity levels were measured with the Community Healthy Activities Model Program
for Seniors questionnaire, a well-validated measure of physical activity among middle-aged and
older adults [CHAMPS: 13]. High levels of exercise are associated with better cognitive function
Supplemental Digital Content 1 for Psychosomatic Medicine
[14]. Accordingly, the exercise index allowed us to examine the links between loneliness and
cognitive function, independent of activity levels.
To assess social integration versus isolation, participants completed the Social Network
Index Interview [SNII; 15]. The SNII, a commonly used measure of social integration, asks
participants to indicate whether or not they are in different types of relationships and have
different social roles. This measure was included to disentangle the presence/absence of a
relationship (i.e., social integration) versus the perceived quality of those relationships (i.e.,
loneliness).1
Participants answered questions about their age, marital status, weekly average alcohol
consumption, current medication use, and education. Years of education was used as an index of
SES because some people in our sample did not work outside of the home. In addition, education
is less vulnerable to current economic conditions than income and job status. We also assessed
participants’ body mass index (BMI: kg/m2).
1
The SNII was administered 4 weeks after supplementation began (i.e.,12 weeks before trial
completion), at the same time as the loneliness measure. As noted in eTable 1, there were no
differences in social integration across groups. Accordingly, the SNII was used as a baseline
measure of social integration.
Supplemental Digital Content 1 for Psychosomatic Medicine
Testing Inflammation as a Potential Mediator
The primary paper that resulted from the parent RCT demonstrated that omega-3
supplementation caused reductions in inflammation over time [16]. Specifically, serum
interleukin-6 (IL-6) decreased by 10% and 12% in the 1.25 g/d and 2.50 g/d imega-3 groups,
respectively, compared to a 36% increase in the placebo group. Similarly, the 1.25 g/d and 2.50
g/d omega-3 groups showed modest 0.2% and 2.3% changes in serum tumor necrosis factor
alpha (TNF-α), compared to a 12% increase in the placebo group.
Loneliness is linked to elevated inflammation and inflammation may promote cognitive
difficulties [17,18]. Accordingly, we explored whether decreased inflammation may partially
explain why omega-3 supplementation attenuated loneliness-related episodic memory problems
in the current study. To test this possibility, we ran a series of analyses exploring the links among
loneliness, omega-3 supplementation, inflammation, and episodic memory. Similar to the
primary analyses, we controlled for marital status BMI, activity levels, and baseline levels of the
corresponding outcome. The interaction between loneliness and supplementation group was
unrelated to post-supplementation inflammation IL-6 and TNF-α, F(2,114) = 1.35, p = .264 and
F(2,119) = 0.81, p = .446 respectively. In addition, changes in both IL-6 and TNF-α were
unrelated to post-supplementation immediate and long-delay free recall, independent of baseline
levels, all p values > .134. Collectively, these results suggest that changes in inflammation did
not explain why lonely participants benefited from omega-3 supplementation.
Supplemental Digital Content 1 for Psychosomatic Medicine
eTable 1. Baseline sample characteristics for the primary study variables.
Characteristic
Full Sample
Placebo
1.25 g/d
2.50 g/d
p-value
Mean(SD)
Mean(SD)
Mean(SD)
Mean(SD)
Loneliness
37.86(9.83)
37.82(10.42)
36.00(8.29)
39.88(10.54)
.177
BMI
30.59(4.50)
29.76(4.73)
31.83(4.66)
30.18(3.88)
.065
Hours of activity/week
11.11(5.83)
10.09(4.96)
13.04(6.66)
10.20(5.35)
.021
Social integration
7.89(1.86)
7.58(2.04)
7.94(1.48)
8.16(2.03)
.334
Sleep quality
5.47(2.85)
5.40(2.47)
5.26(2.66)
5.76(3.37)
.689
Alcoholic drinks/week
1.57(2.69)
1.63(3.06)
1.26(1.69)
1.80(3.10)
.616
Depressive symptoms
7.58(8.10)
7.70(9.08)
7.70(8.69)
7.35(6.44)
.972
CVLT – immediate
56.77(9.82)
58.07(9.29)
54.60(11.30)
57.62(8.51)
.189
CVLT – short delay
11.89(2.77)
12.26(2.80)
11.18(3.05)
12.22(2.33)
.107
CVLT – long delay
12.58(2.58)
12.96(2.36)
11.73(2.94)
13.05(2.24)
.026
Digit Span
17.50(3.94)
17.02(3.94)
17.09(3.86)
18.43(3.94)
.162
Letter-Number Sequencing
11.03(2.36)
10.61(1.92)
10.63(1.99)
11.89(2.90)
.013
Spatial Span
16.26(2.81)
16.30(2.40)
15.57(2.80)
16.95(3.09)
.063
Trail Making (B-A)
37.23(23.34)
35.87(18.68)
43.30(31.93)
32.42(14.87)
.074
Controlled Oral Word Association Task
41.47(11.37)
42.37(9.52)
37.33(10.12)
44.78(13.13)
.005
NOTE: The p-value refers to the test of between group differences at baseline, which were tested with unadjusted models.
Supplemental Digital Content 1 for Psychosomatic Medicine
eTable 2. Significance test and effect sizes for the loneliness by supplementation group interaction predicting cognitive function scores
Model 1
Model 2
F
df
p value
R2
F
df
p value
R2
CVLT – immediate
2.69
2,121
.072
.02
5.05
2,117
.008
.04
CVLT – short delay
0.45
2,121
.637
.01
0.90
2,117
.411
.01
CVLT – long delay
2.74
2,120
.068
.02
3.38
2,116
.038
.03
Digit Span
0.19
2,122
.830
.00
0.13
2,118
.881
.00
Letter-Number Sequencing
1.54
2,122
.219
.01
1.15
2,118
.322
.01
Spatial Span
0.84
2,122
.436
.01
0.88
2,118
.419
.01
Trail Making (B-A)
1.33
2,121
.269
.01
0.96
2,117
.386
.01
Controlled Oral Word Association Task
0.24
2,122
.787
.00
0.22
2,118
.802
.00
Outcome
NOTE: The R2 reflects the proportion of variance explained in the outcome by the interaction between loneliness and omega-3
supplementation group. Model 1 included the baseline cognitive function scores, loneliness, group, and the loneliness by group
interaction as predictors. Model 2 also included marital status, BMI, and activity levels, as reported in the primary analyses.
Supplemental Digital Content 1 for Psychosomatic Medicine
eTable 3. Significance test for the main effect of supplementation group predicting cognitive function scores
Characteristic
Placebo
1.25 g/d
2.50 g/d
F
df
p-value
Mean(SE)
Mean(SE)
Mean(SE)
CVLT – immediate
58.05(1.11)
54.32(1.36)
58.29(1.25)
3.60
2,117
.030
CVLT – short delay
12.38(0.36)
11.98(0.45)
12.62(0.41)
0.72
2,117
.490
CVLT – long delay
12.87(0.30)
12.59(0.38)
13.25(0.34)
1.09
2,116
.341
Digit Span
18.09(0.39)
17.98(0.47)
18.43(0.45)
0.37
2,118
.695
Letter-Number Sequencing
11.02(0.27)
11.05(0.33)
11.46(0.31)
0.74
2,118
.479
Spatial Span
16.84(0.34)
16.60(0.41)
16.35(0.39)
0.49
2,118
.615
Trail Making (B-A)
35.67(2.31)
35.09(2.87)
35.84(2.63)
0.03
2,117
.974
Controlled Oral Word Association Task
42.35(0.98)
43.45(1.21)
43.41(1.12)
0.38
2,118
.683
NOTE: The means, standard errors (SE), and test statistics were derived from the model reported in the primary analyses. These
analyses included baseline cognitive function scores, marital status, BMI, and activity levels, loneliness, group, and the loneliness by
group interaction as predictors.
Supplemental Digital Content 1 for Psychosomatic Medicine
eTable 4. Planned contrasts examining the effect of supplementation on immediate and long-delay recall for people who were more or
less lonely
Outcome
Loneliness Score
(a)
(b)
(c)
(a) vs (b)
(a) vs (c)
(b) vs (c)
Placebo
1.25 g/d
2.50 g/d
p value
p value
p value
Less lonely (-1 SD)
60.84(1.54)
56.37(1.68)
56.57(1.82)
.041
.063
.929
More lonely (+1 SD)
55.30(1.52)
52.29(2.12)
59.99(1.42)
.245
.022
.002
Less lonely (-1 SD)
13.47(0.42)
12.68(0.46)
12.79(0.51)
.184
.278
.861
More lonely (+1 SD)
12.28(0.41)
12.51(0.58)
13.70(0.39)
.743
.011
.079
CVLT – immediate
CVLT – long delay
NOTE: The values presented in columns a, b, and c are the estimated marginal means and standard errors of the mean for each group,
which correspond to the values plotted in Figures 1 and 2. Each estimated marginal mean was obtained from the adjusted model
presented in the primary analyses for people who were one standard deviation above and below the mean of loneliness.
Supplemental Digital Content 1 for Psychosomatic Medicine
eTable 5. Residual change in cognitive function scores from pre to post supplementation.
Outcome
Supplementation Group
Loneliness Score
Pre to Post Supplementation Change
Mean(SE)
Less lonely (-1 SD)
4.31(1.54)
More lonely (+1 SD)
-1.23(1.52)
Less lonely (-1 SD)
-0.16(1.68)
More lonely (+1 SD)
-4.24(2.12)
Less lonely (-1 SD)
0.04(1.82)
More lonely (+1 SD)
3.46(1.42)
Less lonely (-1 SD)
0.92(0.42)
More lonely (+1 SD)
-0.27(0.41)
Less lonely (-1 SD)
0.13(0.46)
More lonely (+1 SD)
-0.04(0.58)
Less lonely (-1 SD)
0.24(0.51)
More lonely (+1 SD)
1.15(0.39)
Placebo
CVLT - immediate
1.25 g/d omega-3
2.50 g/d omega-3
Placebo
CVLT – long delay
1.25 g/d omega-3
2.50 g/d omega-3
NOTE: Only the cognitive functions measures with significant loneliness by group interactions are reported. The values were derived
from the adjusted models presented in the primary analyses.
Supplemental Digital Content 1 for Psychosomatic Medicine
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