2012. Vol.3, No.12A, 1223-1230
Published Online December 2012 in SciRes (http://www.SciRP.org/journal/psych) http://dx.doi.org/10.4236/psych.2012.312A181
Copyright © 2012 SciRes. 1223
Social Support and Sleep. Longitudinal Relationships from the
Maria Nordin1*, Peter Westerho lm2, Lars Alfredsson3, Torbjörn Åkerstedt4
1Department of Psychology, Um e å University, Umeå, Sweden
2Uppsala University, Uppsala, Sweden
3Karolinska Institutet, Stockholm, Sweden
4Stress Research Institute, Stockholm, Sweden
Received September 14th, 2012; revised October 18th, 2012; accept e d N o v e mber 19th, 2012
Aim: To investigate the relationship between two social support dimensions (network and emotional
support) and sleep quality and between two social support sources (at and outside work) and sleep quality.
Methods: The three-wave prospective Work Lipids and Fibrinogen (WOLF) study from Northern Swe-
den was used including 2420 participants who had filled out a questionnaire on working life, life style and
health. Sleep quality was assessed by the Karolinska Sleep Questionnaire (KSQ). Structure and function
of social support were measured as network support both at and outside work by Availability of Social
Integration (AVSI) and emotional support both at and outside work by Availability of Attachment
(AVAT). Logistic regression was used, utilizing variables created to assess development over time.
Moreover, reversed causation was tested. Results: Improved network support at work decreased the risk
of disturbed sleep (OR .65; 95% CI .47 - .90) as did improved emotional support outside work (OR .69; 95%
CI .49 - .96). Reporting a constant poor network support at work increased the risk of disturbed sleep (OR
1.53, 95% CI 1.10 - 2.11) as did reporting a constant poor emotional support outside work (OR 1.46; 95%
CI 1.02 - 2.05). In men constant good network at work decreased the risk of disturbed sleep (OR .49, 95%
CI .34 - .71). Reversed causation analyses indicate some bi-directionality. Conclusion: Being able to per-
ceive social support is a human strength promoting sleep. Both dimension (structure and function) and
source (at and outside work) of support matters in sleep quality and seem to be related since the structural
dimension was more likely to affect sleep when derived from work, whereas the functional dimension af-
fected sleep quality if it was provided outside work. Men’s sleep seems to be more sensitive to network
support at work. Disturbed sleep may also alter the perception of social support.
Keywords: Sleep Quality; KSQ; Social Integration; Emotional Support; Reversed Causation
To perceive social support from friend s and family as positi ve
is a psychological strength that provides stress reducing and
health beneficial effects (House, Landis, & Umberson, 1988;
Mankowski & Wyer, 1997). Another important health promoter
is good sleep. However, about 25% of the population in the
Western hemisphere (e.g., Ohayon, 1997) suffers from sleep
disturbances, a problem that may lead to more serious diseases
(e.g., Schwartz et al. 1999; Tsuno, Besset, & Richier, 2005).
Previous findings indicate that social support and sleep have
stress as a common denominator. Sleep is depicted as the oppo-
site of stress since sleep is easily disturbed by stress (Healy,
Kales, Monroe, Bixler, Chamberlain, & Soldatos, 1983; Ekstedt,
2005), whereas social support is a well-known and well-inves-
tigated stress reliever (e.g., Berkman & Syme, 1979; House,
Landis, & Umberson, 1988; Cohen, Underwood, & Gottlieb,
2000). Cross-sectional associations have been found between
social support and sleep (e.g., Nakata, Haratani, Tkahashi, Ka-
wakami, Arito, Fujioka et al., 2001; Nordin, Knutsson, Sund-
bom, & Stegmayr, 2005; Nordin, Sundbom, & Knutsson, 2008;
Pelfrene et al., 2002), and Wahlstedt and Edling (1997) con-
cluded in their longitudinal study that individuals who per-
ceived impaired contacts with coworkers and/or supervisors
had a higher risk of reporting disturbed sleep. Moreover, Si-
nokki, Ahola, Hinkka, Sallinen, Härmä, Puukka et al. (2010)
concluded in a longitudinal study on a representative Finnish
sample, that low social support especially at work was related
to disturbed sleep.
Social support is a dynamic process that provides comfort
and aid from friends, family and coworkers. Social support can
be divided into its structure and its function. The structure deals
with the quantity of network of friends, family and co-workers
(House, Landis, & Umberson, 1988). Previous research has
consistently showed a positive correlation between network
size and health (Cohen, Underwood, & Gottlieb, 2000) and
Brugha, Weich, Singleton, Lewis, Bebbington, Jenkins et al.
(2005), found that a network including more than three persons
was beneficial for mental health. The function of social support
entails the more qualitative aspects of support, emotional sup-
port presumably being the most important dimension (House,
Landis, & Umberson, 1988). Encouragement and comfort, two
main ingredients in emotional support, are considered to be of
great importance in maintaining health and well-being (Cohen,
Underwood, & Gottlieb, 2000).
Some studies have shown the importance of social support at
work in the relationship with sleep (Nakata et al., 2001; Nordin
M. NORDIN ET AL.
et al. 2005; Wahlstedt & Edling, 1997; Sinokki et al., 2010;
Pelfrene et al., 2002). Another important source for support is
the life outside work, containing family and friends and studies
have shown positive relationships between social support from
the realm outside working life and sleep (Hanson & Östergren,
1987; Ohayon et al., 1997; Tynjälä et al., 1999), especially in
disease (Nordin e t al., 2008; Vosvick et al., 2004).
Even though there are quite a few studies confirming a rela-
tionship between social support and sleep, no study has to our
knowledge investigated the relationship more at depth by study-
ing how central dimensions (such as network and emotional
support) develop over time and what matter sources (such as at
work and outside work) of support play in sleep. Therefore, the
aim of the present study is twofold as it is to, in a longitudinal
design, 1) investigate if the development over time in the two
social support dimensions, network and emotional support are
related to sleep; and 2) investigate if social support from dif-
ferent sources, work and outside work, matter in sleep. The
general hypothesis that has been tested so far in previous re-
search is that social support affects sleep and not the other way
around. It is however possible that the lack of energy that poor
sleep will contribute to and the bad mood that can be associated
with disturbed sleep (Pilcher & Huffcutt, 1996) affects the pos-
sibility to appreciate coworkers, friends and families. Therefore,
reversed analyses are conducted. Because more women report
disturbed sleep (Ohayon, 1997) and are considered to have
more sources of support since they have been shown to act on
more arenas than men (Antonucci, 1994), sex is taken into con-
In the present study, the Work Lipids and Fibrinogen
(WOLF) study from Northern Sweden, a three-wave prospec-
tive epidemiological study is used. This three-wave design
makes it possible to study both how development in social sup-
port affects sleep quality in a long-term perspective, and if there
is reversed causation in this relationship.
Design and Participants
The present study is based on the WOLF-Norrland study
(WOLF-N). The WOLF-N study is a prospective cohort study
that aims at investigating the effects of psychosocial work fac-
tors and life style on health. All Occupational Health Service
units (OHS) in Västernorrland and Jämtland, two provinces in
Northern Sweden, were invited to participate between the years
1996 and 1998 (T0). The OHS:s offered a health examination
to all the employees served by them and administered ques-
tionnaires for the employees to fill out. Fifteen OHS organiza-
tions participated and the personnel were trained in standard-
ized measurement procedures. The participants were re-invited
to two follow-ups; T1, between 2000 and 2003 and T2, in-
cluding only a questionnaire, in the fall of 2009. Up to three
reminders were sent in both follow-up studies, unless the par-
ticipant actively declined to participate.
The original sample at T0 consisted of 5092 individuals, out
of whom 4715 (93%) responded. The follow-up response rate at
T1 was 71%, i.e., 3637 participants. At T2, 2821 (60% from T0;
77% from T1) had filled out the given questionnaire, thus hav-
ing participated three times in the WOLF-Norrland study. The
mean time elapsed between T0 and T1 was five years (±11
months) and between T1 and T2 seven years (±6 months). The
sample demographics are presented in Tables 1 and 2. Ethical
approval was obtained from the ethical committee at Karolinska
Outcome an d Pr e d ic t o r Variables Sle ep
The sleep quality index in the Karolinska Sleep Question-
naire (KSQ; Åkerstedt, Ingre, Broman, & Kecklund, 2008) was
used as both a predictor and an outcome variable in this study.
The items included were: difficulties falling asleep, restless
sleep, repeated awakenings, and premature awakening and the
response alternatives ranged from “never” to “most days of the
week” (with values from 1 - 5 assigned) the past twelve months
(T0 and T1) and the past three months (T2). Internal consis-
tency was high with Cronbach’s alphas of .78 at T0, .82 at T1,
and .84 at T2. Each question in the sleep quality index was
dichotomized so that the response alternatives “a few times per
week” and “every night” were identified as disturbed sleep and
coded with the number 1 leaving the other response alternatives
coded with 0. Thereafter, the four questions included were
summed into a sleepy quality index and those scoring one to
four (i.e. had any of the symptoms) were identified with dis-
turbed sleep. The criterion was set to be similar to that of insom-
nia (Buysse, Ancoli-Israel, Edinger, Lichstein, & Morin, 2006).
New cases of disturbed sleep were identified as those who re-
ported disturbed sleep according to the definition above at T2
but not at T0 and T1.
Social Support; Dimensions and Sources
The structural dimension of social support was represented
by the Swedish version of Availability of Social Integration
(AVSI; Henderson, Duncan-Jones, Byrne, & Scott, 1981;
Undén & Orth-Gomér, 1989) measuring network support. The
questions “There are people in my surrounding I easily can ask
for things from, for example borrow tools or kitchen ware” and
“Apart from those at home, there are others I can turn to in
need” were excluded from this index, since they loaded on a
separate factor in a factor analysis and lowered the internal reli-
ability to unsatisfactory levels (a pattern previously shown in
another sample; Nordin et al., 2008). The questions on how
many friends that were available in different situations were
asked both in the context of the work place and outside work
and measured on a scale with the response alternatives: none, 1 -
2, 3 - 5, 6 - 10, 11 - 15 and more than 15. Thus, two indexes
were formed; network support from the source at work (where
the summed index was dichotomized at the first quartile [iden-
tified at T0 and used on all occasions, i.e., T0, T1 and T2, for
comparative reasons] between scale scores 10 and 11), and
network support outside work, dichotomized at the first quartile
(identified at T0 and used on all occasions for comparative
reasons) between 11 and 12. This dichotomy equals a cut be-
tween five and six friends.
The functional dimension of social support was represented
by the Swedish version of Availability of Attachment (AVAT;
Henderson et al., 1981; Undén & Orth-Gomér, 1989) measure-
ing emotional support. The questions were asked both in the
context of the work place and outside work. Thus, two indexes
were formed, emotional support from the source at work (where
the summed indexed was dichotomized at the first quartile
[identified at T0 and used on all occasions for comparative
reasons] between scale scores 5 and 6), and emotional support
from the source outside work (dichotomized at the first
Copyright © 2012 SciRes.
M. NORDIN ET AL.
Copyright © 2012 SciRes. 1225
Frequencies, prevalenc e s , means and standard deviations o f t h e s t u d i e d v a riables.
T0 T1 T2
n % n % n %
Outcome and predictor variables
No 1642 8.8 1414 7.5 1612 73.1
Yes 390 19.2 592 29.5 593 26.9
Social network at work
Large 1373 68.9 1230 63.8 911 6.1
Small 620 31.1 698 86.2 606 39.9
Social network outside work
Large 1785 88.2 1715 86.3 1797 79.7
Small 239 11.8 272 13.7 458 2.3
Emotional sup port at wor k
Yes 1581 78.4 1548 78.9 1219 79.7
No 435 21.6 414 21.1 310 2.3
Emotional sup por t outside wor k
Yes 1512 74.3 1459 72.8 1531 66.7
No 524 25.7 545 27.2 764 33.3
Man 1987 82.1 1987 82.1
Woman 433 17.9 433 17.9
University 463 16.8 335 16.8
No university 1710 83.2 1655 83.2
Age (m ± sd) 43.4 ± 8.7 5.1 ± 9.8
Young 1058 51.4 721 29.8
Old 1001 48.6 1698 7.2
Married 1648 8.1 1669 81.6
Unmarried 409 19.9 376 18.4
No 1774 86.5 1777 87.5
Yes 277 13.5 253 12.5
Children at home
Yes 772 37.6 971 47.8
No 1279 62.4 1059 52.2
Demands at work
Low 1433 7.5 1376 68.5
High 600 24.8 634 31.5
Control at work
Low 1310 64.0 1371 67.9
High 738 36.0 648 32.1
No 1347 65.5 1368 67.4
Yes 710 34.5 662 32.6
M. NORDIN ET AL.
quartile [identified at T0 and used on al occasions for compara-
tive reasons] between 8 and 9).
Confound in g Va riables
Sex and age were assessed by single questions. Education
was assessed by the question “Which one of the following
schools/educations have you attended?” The response alterna-
tive “university education” was contrasted with the other alter-
natives given. For marital status the response alternatives
“married/cohabiting” was contrasted with “single”, “divorced”,
and “widow/widower” in combination. Living alone was as-
sessed by the question “Do you live alone?” and the response
alternative yes was contrasted with the alternatives living with a
partner, with children, or with parents. Having children at home
was estimated by the question “Do you have children living at
home?” with the response alternatives yes and no. Demand and
control at work were estimated by the Swedish version of the
Job Strain Questionnaire (JSQ) based on the demand-con- trol
model postulated by Karasek and Theorell (1990). As for the
demand dimension, the five included questions were summed.
For comparative reasons, the distribution at T0 was used as
base for identifying those perceiving high demands at work at
T0, T1 and T2 and separating them from the rest. The control at
work index was treated as one dimension in the same way as
the demand index in that T0 was used as base for identifying
those reporting low control. A summary score was derived from
the answers to the six questions included and the index was
subsequently dichotomized on the highest quartile given the
reversed scale. Shift work was measured with the question “Do
you work shifts?” with the response alternatives “no”, con-
trasted with “yes” (including the alternatives: 2-shift, continu-
ous 3-shift, irregular work schedule without night shift, irregu-
lar work schedule with night shifts, permanent night work,
other type of shift work). Loss of a work place changes ones
source of social support. Therefore, retirement was considered
by the response alternative retired to the question “What is your
current occupation?” at T2.
The procedures undertaken to create the variables were the
same at T0, T1 and T2. Moreover, variables measuring devel-
opment (i.e., both change a nd consistency over time) across the
five years of follow-up between T0 and T1 were created for
participants where data from both occasions were obtained.
Thus, development variables were created for all the social
support variables, the sleep quality variable, education, marital
status, demand at work, control at work, and shift work by
combining the dichotomized variables presented above into
four categories; positive responses at both T0 and T1, negative
response at T0 and positive response at T1, positive response at
T0 and negative response at T1, and negative responses at both
T0 and T1 (see Table 2 for their respective distributions).
Development in age was created by first dichotomizing the
age variables on the median age at T0 (44 years) and subse-
quently combining the variables into below 44 at T0 and T1,
below 44 at T0 and above at T1, and above 44 at both T0 and
T1 (see Table 2).
Spearman’s rho was used to estimate correlations between
the variables for selection of confounding variables. Logistic
regression analyses were used to estimate odds ratios with 95%
Changes in predictor, outcome and confound ing variables.
Unchanged good sleep T 0 & T1 126163.6
Disturbed at T0 - good at T 1 141 7.1
Good at T0 - disturbed at T1 345 17.4
Unchanged disturbed sleep T0 & T1 236 11.9
ort at work
Unchanged large netw ork T0 - T1 991 52.8
Small network T0 - large network T1 203 1.8
Large network T0 - small network T1 313 16.7
Unchanged small network T0 - T1 369 19.7
Unchanged large netw ork T0 - T1 158781.1
Small network T0 - large network T1 106 5.4
Large network T0 - small network T1 142 7.3
Unchanged small network T0 - T1 122 6.2
ort at work
Unchanged adequate T0 & T1 132268.7
Inadequate T0 - adequate T1 195 1.1
Adequate T0 - inadequa t e T1 189 9.8
Unchanged inadequate T0 & T1 217 11.3
Unchanged adequate T0 & T1 122061.6
Inadequate T0 - adequate T1 227 11.5
Adequate T0 - inadequate T1 255 12.5
Unchanged inadequate T0 & T1 280 14.1
Unchanged high 297 14.9
Low T0 - high T1 41 2.1
Unchanged low 161281.1
Below 42 T0 - above 42 T1 682 33.1
Above 42 T0 & T1 376 18.3
Below 42 T0 & T1 998 48.5
Married T0 & T1 153775.2
Not married T0 - married T1 131 6.4
Married T0 - not married T1 101 4.9
Unmarried T0 & T1 274 13.4
Not living a l on e T0 & T1 167382.7
Living alone T0- not livi ng alone T1 99 4.9
Not living alone T0-living alone T1 77 3.8
Living alone T0 & T1 173 8.6
Children at home
No children a t home T0 & T1 632 31.3
Children a t home T0 - no children at home T1 333 16.5
No children at home T0 - Children at home T1 131 6.5
Children a t home T0 & T 1 926 45.8
Demands at work
Low T0 & T 1 112256.6
Low T0 - high T1 239 12.0
High T0 - low T1 280 14.1
High T0 & T1 343 17.3
Control at work
High T0 & T1 108253.9
Low T0 - high T1 282 14.0
High T0 - low T1 205 1.2
Low T0 & T 1 439 21.9
No shift T0 & T1 126 862.5
Shift T0 - no shift T1 99 4.9
No shift T0 - shift T1 69 3.4
Shift T0 & T1 592 29.2
Copyright © 2012 SciRes.
M. NORDIN ET AL.
confidence interval. In testing the relationship between social
support and sleep quality four models were created for each
predictor-outcome combination: Model I, a crude model; Model
II, adjusted for baseline sleep/social support (depending on
tested direction); Model III, Model II + the social life variables
that correlated with each predictor variable respectively, and
Model IV (only for the analyses referring to the source at work),
Model III + the working life variables correlating to each pre-
dictor variable respectively. Analyses were conducted by both
testing social support as the predicting factor and sleep as the
outcome and vice versa, i.e., sleep as the predicting factor and
social support as the outcome (see e.g., Kivimäki, Virtanen,
Vartia, Elovainio, Vahtera, & Keltinkangas-Järvinen, 2003).
All analyses were conducted using SPSS 18.0 work package.
In this three-wave follow-up study, the prevalence of dis-
turbed sleep increases between T0 and T1 but decreases some-
what at T2 (see Table 1). The incidence proportion of disturbed
sleep between T0 and T2 (1997-2002) is 21.2% (n = 504), be-
tween T1 and T2 (2002-2009) 22.5% (n = 352), and between
T0 and T2 (1997-2009) 18.2% (n = 246). Moreover, the preva-
lence of small networks increases as does the report of low
emotional support at T2 compared to T0 and T1 (see Table 1).
Table 2 shows the distribution of the development variables.
Almost a fifth of the sample reports impaired sleep quality
whereas seven per cent report an improvement in sleep quality
over time. About 12% report an unchanged poor sleep quality,
although the vast majority (63.6%) reports unchanged good
sleep quality. Regarding development of social support, a larger
change is reported in network support at work than outside
work whereas a larger change is reported in emotional support
outside work than in emotional support at work.
Reporting an increase in network support at work and more
emotional support outside work over time decreases the risk of
disturbed sleep at T2. Moreover, reporting constantly low net-
work support at work as well as constantly poor emotional
support outside work increases the risk of disturbed sleep at T2.
A decrease in network support at work also increases the risk of
disturbed sleep, but when controlling for development in social
life outside work this risk falls to insignificance (see Table 3).
It is plausible that poor sleep contributes to lack of energy
and bad mood, which may affect the ability to appreciate
friends and families. Reversing the analyses shows that con-
stant poor sleep quality increases the risk of reporting low net-
work support outside work (Model I OR 1.83, 95% CI 1.32 -
2.53; Model II [adjusted for network support at baseline] OR
1.59, 95% CI 1.10 - 2.31; Model III [Model II + adjusted for
sex] OR 1.62, 95% 1.12 - 2.36; Model IV [Model III + adjusted
for demand and control] OR 1.58, 95 % CI 1.07 - 2.33) whereas
improved sleep quality decreases this risk (Model I OR .55,
95% CI .40 - .76; Model II [adjusted for network support at
baseline] OR .63, 95% CI .43 - .91; Model III [Model II + ad-
justed for sex] OR .62, 95% .42 - .90; Model IV [Model III +
adjusted for demand and control] OR .63, 95 % CI .43 - .94).
To investigate potential differences between men and women
in the relationship between social support an sleep, interaction
analyses were performed. Interaction effects were found be-
tween sex and constant good network support at work (OR .47,
95% CI .22 - 1.00) and post hoc analyses showed the risk of
disturbed sleep being lowered in men reporting constantly good
network support at work (Model I: OR .52, 95% CI .38 - .71;
Model II [Model I + adjustment for change in sleep between T0
and T1]: OR .51, 95% CI .36 - .72; Model III [Model II + ad-
justment for change in partnership and living alone]: OR .50,
95% CI .35 - .71; Model IV [Model III + adjustment for change
in demand, contro l and shift work]: OR . 49, 95% CI .34 - .71).
No relationship was found between good network support and
sleep in women.
The health beneficial power of social support is clearly
shown in this study since both an increase in the number of
network members at work and improved emotional support
outside work reduced the risk of disturbed sleep. These results
are to our knowledge, the first to show that an increase and an
improvement in social support may help reducing sleeping
problems. Both dimension (network and emotional support)
and support sources (at work and outside work) were associated
with sleep. In fact, dimension and source seemed to be related
as sleep was more likely to be affected by network support at
work but by emotional support from the realm outside work.
Moreover, a bi-directional relationship was indicated by poor
network support outside work increasing the risk of poor sleep
Dimensions: Structure and Function
Network support has previously been shown to be the more
important dimension of the two under study in relation to sleep
disturbances (Nordin et al., 2005; Nordin et al., 2008). Given
the previous research showing the structural dimension of so-
cial support being closely related to health (Cohen, Underwood,
& Gottlieb, 2000; House, Landis, & Umberson, 1988), these
results are logical. However, even if in line with previous the-
ory and research on general health (ibid.), the effect that emo-
tional support outside work had on sleep quality has, to the best
of our knowledge, not been shown before and is therefore espe-
cially interest i ng and important.
Sources: W ork and Outside Work
This study supports both the longitudinal studies by Wahl-
stedt & Edling (1997) and Sinokki et al. (2010) in that network
support at work is related to sleep. Taken together, these results
are important. Given the link between sleep and other diseases
(e.g., Schwartz et al. 1999; Tsuno, Besset, & Richier, 2005),
sleep disturbance caused by poor organizational structures or
lack of understanding of social relations at work may lead to
sick leaves, costly both for the company and the individual.
Interestingly though, our results also suggest that an increase in
the numbers of coworkers in the network at work may promote
better sleep. The mechanisms here need to be more thoroughly
investigated and it is important to point out that the individuals’
interpretation of what resources are at hands (Mankowski &
Wyer, 1997) also play a significant role in the response patterns
given in studies like these. However, the results again confirm
previous research on the beneficial power in social support.
This study also adds that social support outside work is im-
portant. Sinooki et al., (2010) showed that a structural mea-
sure of social support (similar to our measure of network sup-
port) outside work was important for sleep. However, as men-
tioned above, the fact that emotional support outside work is
Copyright © 2012 SciRes. 1227
M. NORDIN ET AL.
Copyright © 2012 SciRes.
Disturbed sleep at T2 predicted by change in social support variables summarized in models and presented as odds ratios and confidence intervals by
Model I Model II Model III Model IV
OR CI OR CI OR CI OR CI
NETWORK SUPPORT AT WORK
Unchanged poor 1 1 1 1
Poor at T0 - good at T1 .57 .43 - .75 .60 .44 - .81 .59 .43 - .80a .65 .47 - .90a
Good at T0 & T1 .84 .57 - 1.24 1.08 .71 - 1.64 1.07 .70 - 1.64a 1.14 .73 - 1.73a
Good at T0 & T1 1 1 1 1
Good at T0- poor at T2 1.51 1.12 - 2.03 1.45 1.05 - 2. 00 1.44 1.04 - 1.99a 1.38 .98 - 1.93a
Poor at T0 & T1 1.76 1.34 - 2.32 1.68 1.24 - 2.27 1.71 1.26 - 2.32a 1.53 1.10 - 2.11a
NETWORK SUPPORT OUTSIDE WORK
Unchanged poor 1 1 1 1
Poor at T0 - good at T1 .65 .43 - .99 .69 .44 - 1.09 .67 .43 - 1.06b .74 .46 - 1.19b
Good at T0 & T1 .74 .41 - 1.33 .86 .45 - 1.62 .84 .44 - 1.60b .30 .49 - 1.80b
Good at T0 & T1 1 1 1 1
Good at T0 - p oor at T1 1.16 .78 - 1.73 1.05 .68 - 1.63 1.09 .70 - 1.68b 1.07 .68 - 1.66b
Poor at T0 & T1 1.54 1.01 - 2.33 1.44 .92 - 2.26 1.48 .94 - 2.33b 1.36 .84 - 2.18b
EMOTIONAL SUPPORT AT WORK
Unchanged poor 1 1 1 1
Poor at T0 - good at T1 .71 .51 - .99 .82 .57 - 1.17 .80 .56 - 1.16c .90 .62 - 1.3 1c
Good at T0 & T1 .84 .54 - 1.31 .94 .58 - 1.52 . 94 .58 - 1.51c .94 .57 - 1.5 4c
Good at T0 & T1 1 1 1 1
Good at T0 - p oor at T1 1.15 .81 - 1.64 1.18 .81 - 1.71 1.19 .82 - 1.74c 1.15 .79 - 1.69c
Poor at T0 & T1 1.41 1.01 - 1.96 1.23 .85 - 1.76 1.24 .87 - 1.79c 1.12 .77 - 1.62c
EMOTIONAL SUPPORT OUTSIDE WORK
Unchanged poor 1 1 1 1
Poor at T0 - good at T1 .69 .51 - .92 .71 .51 - .97 .67 .48 - .92d .69 .49 - .96d
Good at T0 & T1 .91 .62 - 1.35 .93 .61 - 1.43 . 99 .58 - 1.36d .90 .57 - 1.40d
Good at T0 & T1 1 1 1 1
Good at T0 - p oor at T1 1.04 .75 - 1.43 .99 .70 - 1.40 .98 .69 - 1.36d 1.02 .71 - 1.46d
Poor at T0 & T1 1.46 1.09 - 1.96 1.42 1.03 - 1.95 1.50 .08 - 2.08d 1.46 1.04 - 2.05d
Note: Model I: Crude. Model II: Adjusted for change in disturbed sleep. Model III = Model II + a: change in marriage and living alone; b: change in marriage; c: sex; d:
sex. Model IV = Model III a-d + a: change in demand and control at work; b: change in demand and control at work; c: change in control and shift wo rk; d: change in
demand and control at work, respectively.
associated with sleep is still a new finding.
The dimensions of social support seems to be associated with
source of social support since network support at work most
predominantly showed a relationship with sleep as did emo-
tional support outside work. Cutrona and Russell (1990) sug-
gested that social support must match the stressor to be effec-
tive. If much work is done in collaboration with others, a cer-
tain quantity of coworkers is needed. Thus, being the more
quantitative of the measures, network support may be the most
important one to get the work done properly and a small net-
work (here less than five coworkers) or a diminished network at
work may cause stress, worry and rumination about how to get
the work done. Stress, worry and rumination are known dis-
turbers of sleep (Ekstedt, 2005; Kirkegaard-Thomsen et al.,
Controlling for social life outside work reduced the risk of
disturbed sleep predicted by a decrease in network support at
work to insignificance. This may partly implicate that family
and friends buffer against the stress, worry and rumination that
a diminished network support at work may have caused. Emo-
tional support has been shown to be mostly derived from family
and close friends (Cohen, Underwood, & Gottlieb, 2000) and
the family has been regarded as a universal buffer that can re-
lieve stress and worry from other arenas in life, such as work
(Cutrona & Russell, 1990).
Women have been suggested to live their lives on more are-
nas than men which also mean having more sources to derive
support from. On the other hand, work has been portrayed as
M. NORDIN ET AL.
the most important source of support for men (Shumaker & Hill,
1991). In this light, the increased chance of better sleep due to
the report of constant good network support at work only in
men is not surprising.
Even if causality cannot be established in a study design like
this, the results support the commonly tested hypothesis that
social support affects sleep. However, one result that deserves
special attention is the report of a constant poor sleep quality
increasing the risk of reporting a poor network support outside
work, whereas an improvement of sleep quality decreased this
risk. Speculating on these results, disturbed sleep quality may
deplete energy resources i.e., resources needed to interact with
friends in order to perceive belongingness (Hagerty, Lynch-
Sauer, Patusky, Bouwsema, & Collier, 1992). The energy that
remains, despite a disturbed sleep, may foremost be spent at
work, interacting with coworkers. This prioritization may be
required for the work to run smoothly. However, when return-
ing home, the energy depletion due to disturbed sleep (and
presumably a hard day’s work) may have taken its toll resulting
in the perception of low network support since there is no en-
ergy left to engage in family and friends.
Strengths and Limitati ons
In interpreting the results, strengths and limitations need to
be considered carefully. The fact that the present study is a
three wave longitudinal study is an obvious strength as it gives
the possibility to study changes over time and reversed causa-
tion and consequently elucidate temporal sequence of social
support and sleep. Moreover, the extensive questionnaire in-
cluded in the study give the possibility of careful confounding
control, even if there may be yet other confounding variables at
play than those considered here. However, the long periods in
between the follow-ups (five and seven years respectively) limit
the possibilities to draw conclusions since, especially sleep
quality, may have fluctuated several times over the years due to
different causes. The fact that the women are outnumbered by
the men in this study may have lead to somewhat skewed re-
sults in the interaction analyses. Moreover, the sleep quality
index was not perfectly comparable over the years because at
T0 and T1 the participants were asked to assess their sleep dur-
ing the past 12 months but at T2 this assessment period was
reduced to three months. This may have lead to an underesti-
mation of disturbed sleep according to the criteria of insomnia
at T0 and T1 and diluted the results somewhat.
This study shows that the perception of social support is a
human strength and an asset in promoting sleep. Both dimen-
sion (structure and function) and source (at and outside work)
of support matter in sleep quality and seems to be related since
the structural aspect (network support) is more likely to affect
sleep when derived from work, whereas the functional aspect
(emotional support) affected sleep quality if it was provided
from outside work. Also bi-directional relationships were found
as social support preceded disturbed sleep quality simultane-
ously to disturbed sleep quality preceding the report of per-
ceived social support. More research on how to strengthen both
social support and sleep would benefit health and well-being in
the general population.
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