Associations of a Short Sleep Duration, Insufficient Sleep, and Insomnia with Self-Rated Health among Nurses
Associations of a Short Sleep Duration, Insufficient Sleep, and Insomnia with Self- Rated Health among Nurses
Aline Silva-Costa 0 1 2
Rosane Hrter Griep ) 0 1 2
Lcia Rotenberg 0 1 2
0 1 National School of Public Health, Oswaldo Cruz Foundation-ENSP/FIOCRUZ , Rio de Janeiro , Brazil , 2 Laboratory of Health and Environment Education, Oswaldo Cruz Institute-Fiocruz , Rio de Janeiro , Brazil
1 Funding: RHG and LR are recipients of research productivity grants from CNPq (Brazilian Council for Scientific and Technological Development). RHG and LR are fellows of the Irving Selikoff International Fellows of the Mount Sinai School of Medicine ITREOH Program. Their work was supported in part by grant 1 D43 TW00640 from the Fogarty International Center of the National Institutes of
2 Academic Editor: Christian Cajochen, Centre for Chronobiology , SWITZERLAND
Epidemiological evidence suggests that sleep duration and poor sleep are associated with mortality, as well as with a wide range of negative health outcomes. However, few studies have examined the association between sleep and self-rated health, particularly through the combination of sleep complaints. The objective of this study was to examine whether self-rated health is associated with sleep complaints, considering the combination of sleep duration, insomnia, and sleep sufficiency. This cross-sectional study was performed in the 18 largest public hospitals in the city of Rio de Janeiro, Brazil. A total of 2518 female nurses answered a self-filled multidimensional questionnaire. The adjusted odds ratios and 95% confidence intervals (CIs) estimated the chance of poor self-rated health in the presence of different combinations of sleep duration and quality. Compared with women who reported adequate sleep duration with no sleep quality complaints (reference group), the odds ratios (95% CI) for poor self-rated health were 1.79 (1.27-2.24) for those who reported only insufficient sleep, 1.85 (0.94-3.66) for only a short sleep duration, and 3.12 (1.94-5.01) for only insomnia. Compared with those who expressed all three complaints (short sleep duration, insomnia, and insufficient sleep), the odds ratio for poor self-rated health was 4.49 (3.256.22). Differences in the magnitude of the associations were observed, depending on the combination of sleep complaints. Because self-rated health is a consistent predictor of morbidity, these results reinforce the increasing awareness of the role of sleep in health and disease. Our findings contribute to the recognition of sleep as a public health matter that deserves to be better understood and addressed by policymakers.
Sleep is increasingly recognized as a public health matter because sleep complaints affects
millions of people . The cumulative effects of sleep loss and sleep disorders need to be better
understood and addressed [2,3]. The link between sleep and morbidity has been studied under
Health. Additional financial support: Brazilian National
Research Council (CNPq) and Carlos Chagas Filho
Foundation for Research Support in the State of Rio
de Janeiro (FAPERJ). The funders had no role in
study design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
the field of sleep medicine, which recognizes the importance of clinical characteristics of sleep
Leproult and Van Cauter showed that sleep restriction results in metabolic and endocrine
disorders, such as increased levels of nocturnal cortisol and ghrelin, and decreased leptin levels.
These hormonal alterations might explain the effect of sleep duration on obesity epidemics .
The association of insomnia and the presence of glucose metabolism disorders and high blood
pressure could serve as a potential biological explanation for the increase in cardiovascular
risks observed in the presence of sleep debts and insomnia . This link cannot be described as
a linear cascade; rather, it is a complex and multifactorial process involving a
neuro-endocrinemetabolic network . Several studies have shown that sleep deprivation increases sympathetic
nervous system activity, leading to increased blood pressure and heart rate [8,9]. Suarez et al.
suggested that increased proinflammatory cytokine levels may also be involved in this matter
. Inadequate sleep may increase the cardiovascular risk in apparently healthy individuals
because of activation of inflammatory processes, which could help explain the association
between sleep complaints and cardiovascular morbidity .
Epidemiological evidence suggests that sleep duration and poor quality of sleep are
associated with mortality , as well as with a wide range of negative health outcomes, including
increased risks of hypertension, diabetes, obesity, depression, heart attack, and stroke . A
study on five European countries showed that night waking is associated with hypertension,
cardiovascular diseases, diabetes, and high caffeine consumption . Nagai et al. found
evidence of an association between short sleep duration and diabetes mellitus, hypertension, and
coronary heart disease . A systematic review and meta-analysis of the longitudinal
associations between sleep duration and all-cause mortality showed that a short duration of sleep is
associated with greater risk of death (relative risk: 1.12; 95% confidence interval [CI]: 1.061.18),
with no evidence of publication bias . Grandner et al. highlighted the interaction between
sleep duration and quality, which can increase the cardiometabolic risk . This evidence
indicates the need for considering not only the duration, but also aspects related to the quality of
sleep, such as insomnia and insufficient sleep (fewer hours slept than what one believes to be
sufficient to feel recovered).
Health can be assessed by self-rated health (SRH), which is considered a strong predictor of
morbidity [19,20] and mortality . Despite the consistent association between SRH and
specific health outcomes, SRH has only been used in a few studies on sleep showing
associations of poor self-rated health with insufficient rest/sleep , a short sleep duration [25,26],
and sleep disturbance .
Therefore, the present study aimed to investigate the relationship between sleep and health
considering three aspects of sleep that are potentially harmful to health: a short sleep duration,
insomnia, and insufficient sleep. Health was assessed by SRH. We hypothesized that
individuals who report a short sleep duration combined with insomnia and insufficient sleep are at a
greater risk of reporting poor SRH than those who do not report such sleep problems.
This cross-sectional study was performed in the 18 largest public hospitals in the city of Rio de
Janeiro, Brazil. Data collection occurred from March 2010 to November 2011. Data were
collected during work hours at the hospitals, through a comprehensive self-reported questionnaire
that provided detailed information about the nursing job and health, as well as socioeconomic
The study was briefly explained to participants who were informed that involvement was
completely voluntary and that they could withdraw at any point in time with no negative
consequences. All participants signed consent forms. The protocol was submitted and accepted by
the Oswaldo Cruz Foundation (Fiocruz) Ethics Research Committee.
The eligible study group comprised registered nurses providing assistance to patients at the
hospitals. The nurses were invited to participate through a face-to-face approach by a team of
interviewers . Only female workers were included in analyses (n = 2818) because of gender
differences in sleep complaints . Responses were missing or invalid for 10.7% of the sample.
The final sample included 2518 participants.
1. Sleep variables. - Sleep duration
The self-report questionnaire included the question How many hours of sleep do you get
in a usual nights sleep? Participants were classified according to sleep duration into two
groups: the short sleep duration group ( 6 h) and adequate sleep duration group (79 h)
The following questions were asked: In relation to your sleep during the night, at home,
during the last 4 weeks, how often did you have difficulty in falling asleep?, . . .wake up and
have difficulty going to sleep again?, and . . .wake up before the desired time and not manage
to sleep again? Response alternatives were never/rarely/sometimes (no complaint) and almost
always/always (complaint). Respondents who reported any of the three described complaints
were assigned to the insomniacs group [32,33].
- Sleep sufficiency
Evaluation of insufficient sleep was based on the following questions: How many hours of
sleep do you get in a usual nights sleep? and On average, how many hours of sleep do you
need each night to feel recovered? A difference of 1 h or more was considered to indicate
insufficient sleep . Participants were classified into the sufficient sleep group (those who
sleep enough to feel recovered) or insufficient sleep group (those who sleep less than they
would like to feel recovered).
The exposure variable considered the combination of sleep duration, insomnia, and sleep
sufficiency, comprising eight groups (Table 1). The first four groups included workers who
reported adequate sleep duration, and they were characterized as (i) those who did not report
any sleep complaints (i.e., those who reported an adequate sleep duration, sufficient sleep, and
absence of insomnia), (ii) those who reported only insufficient sleep, (iii) those who reported
only insomnia, and (iv) those who reported insufficient sleep and insomnia. The other groups
were formed by those who reported a short amount of sleep, including (v) those who reported
only short sleep duration, (vi) those who reported short sleep and insomnia, (vii) those who
reported short and insufficient sleep, and (viii) those who reported short and insufficient sleep,
and insomnia (Table 1).
2. Self-rated health. SRH was evaluated by asking, In general, compared with people of
your age, would you say that your health is (. . .), with the following response categories: very
good, good, fair, poor, and very poor. Among the five levels, very good and good were
defined as the healthy group (reference group), while the remaining levels were defined as the
poor SRH group .
Sleep Sufficiency Sufficient Insufficient
CATEGORIES OF SLEEP COMPLAINTS
Descriptive statistics were used to describe exposure categories in relation to sociodemographic
aspects, variables related to work, lifestyle, and health (physical exercise, smoking, age, marital
status, income, professional work hours, shift work, alcohol consumption, caffeine
consumption, sleep satisfaction, and body mass index [BMI]). Categorical variables are expressed as
percentages and continuous variables are expressed as mean (standard deviationSD). The
chisquare test and analysis of variance were used to compare groups (significance level, p < 0.05).
Variables showing at least minimal association (p < 0.10) were selected for inclusion in
Logistic regression analyses were performed to test the association between the exposure
categories and SRH. The first analysis included all exposure groups, thus considering each
complaint separately, as well as a combination of complaints. In this analysis, workers who did
not mention any complaints (group 1) were investigated as the reference group. The second
analysis only included groups with a short sleep duration (groups 5 to 8), and aimed to
determine whether insufficient sleep and insomnia would potentiate the association between short
sleep and poor SRH. The group of those who reported only a short sleep duration (group 5)
was considered as the reference group.
Results are presented as odds ratios and 95% CIs. All statistical analyses were performed
using SPSS software (version 18.0; SPSS Inc., Chicago, IL, USA).
The mean age of participants was 39.9 (SD = 9.8) years (range, 2268 years). Low income
(<495 USD) was reported by 13.7% of the group and high income (>990 USD) was reported
by 42.8%. Insufficient sleep was the most frequent complaint (70.1%), the prevalence of
insomnia was 36%, and 48.6% of the women reported a short sleep duration. A total of 34.4% of
women reported poor SRH.
Characteristics of the participants according to the combination of sleep duration,
insomnia, and insufficient sleep are shown in Tables 2 and 3. Those with all three sleep complaints
reported a higher percentage of poor SRH (51.9%) than did those who did not mention any
complaints (18.9%), (p < 0.001). The prevalence of poor SRH was higher in those who
reported only complaints of insomnia (40.2%) than in those who reported only a short sleep
(30.8%) and only insufficient sleep (28.2%). High proportions of obesity and being married,
and a low proportion of individuals who practiced physical activity were found in women who
reported the combination of insomnia and insufficient sleep.
Table 2. Sociodemographic, occupational, and health characteristics of participants according to the combination of insomnia and insufficient
Sleep 79 hours
Insomnia and insufficient
sleep (n = 202)
Table 4 shows the odds ratios and 95% CIs estimating the chance of poor SRH associated
with different combinations of sleep duration and quality, adjusted for age, income, marital
status, smoking status, alcohol consumption, physical activity, BMI, andwork schedule.
Compared with women who reported an adequate sleep duration (reference group), the odds ratios
for poor SRH were 1.79 (1.272.54) for those who reported only insufficient sleep, 1.85 (0.94
3.66) for only a short sleep duration, and 3.12 (1.945.01) for only insomnia. A significant
interaction (p = 0.002) was observed between insomnia and sleep duration. In relation to the
combined complaints, the odds ratios for poor SRH were 2.20 (1.593.04) for short sleep
combined with insufficient sleep, 3.29 (2.204.93) for insufficient sleep combined with insomnia,
Table 3. Sociodemographic, occupational, and health characteristics of participants according to the combination of short sleep, insufficient
sleep, and insomnia.
Sleep 79 hours
duration (n = 500)
Only short sleep
duration (n = 65)
Short sleep duration (< = 6 hours)
Short sleep and
insomnia (n = 61)
and 4.49 (3.256.22) for all sleep problems together (short sleep duration, insomnia, and
insufficient sleep) (Table 4).
Table 5 shows results concerning women who reported a short sleep duration. There was a
greater chance of reporting poor SRH among those who reported all of the complaints
(OR = 2.40) compared with those who reported only a short sleep duration.
Model 1: unadjusted association; Model 2: adjusted for age, income, marital status; Model 3: adjusted for model 2 + physical activity, alcohol
consumption, coffee consumption, smoking habits, BMI and work schedule.
Poor Self-rated Health Model 2OR (95% CI) 1 1.76 (1.26;2.45)
The current study investigated the combination of quality and duration of sleep in relation to
SRH. We found that all sleep complaints were separately associated with poor SRH. Differences
in the magnitude of the odds ratios for each unique complaint showed that insomnia was the
most strongly associated with poor SRH, followed by a short sleep duration, and insufficient
sleep. We highlight the main contribution of this study, which is the combined analysis of the
quality and duration of sleep in relation to the SRH. Actually, even among individuals who
reported an adequate sleep duration, the combination of insufficient sleep and insomnia was
associated with a high chance of poor SRH (odds ratio = 3.29); inclusion of a short sleep duration
led to an increase in the adjusted odds ratio to 4.49, potentiating the estimates for poor SRH.
These results suggest that sleep duration may interact with sleep quality, intensifying the risk of
Poor Self-rated Health Model 2OR (95% CI) 1 1.29 (0.68;2.47)
Model 1: unadjusted association; Model 2: adjusted for age, income, marital status; Model 3: adjusted for model 2 + smoking habits, physical activity, BMI,
coffee consumption and work schedule.
Other studies have reported an association between a short sleep duration and poor SRH.
Steptoe et al. observed that the adjusted odds ratio (OR) for poor SRH was 1.99 for people
sleeping less than 6 h and 1.56 for those sleeping 6 to 7 h compared with 78 h of daily sleep
. In a large multiethnic sample of US adults, multivariate odds ratios of fair/poor SRH
among women were 2.52 and 1.74 for a sleep duration 5 h and 6 h, respectively, compared
with 7 h of daily sleep . A cross-sectional study of middle-aged and older Australian adults
showed that < 6 h of sleep and 6 h of sleep were associated with poor SRH (odds ratios were
1.49 and 1.28, respectively) .
Sleep quality has also been shown to be associated with SRH. A higher quality of sleep is
associated with a very good (OR = 2.65) and good (OR = 2.88) SRH . The odds ratio for poor
SRH was shown to be 2.6 in those with poor sleep quality . Geiger et al.  showed a
dose-response association of insufficient sleep/rest and SRH. They found that the odds ratio
for poor SHR was 1.45 for 713 days of insufficient sleep/rest, and odds ratios were 2.12, 2.32,
and 2.71 for 1420 days, 1529 days, and 30 days of insufficient sleep/rest, respectively. The
significant association of insufficient sleep/rest and SRH persisted within stratified subgroups
of gender, age, race-ethnicity, and BMI . Data obtained by Grandner et al. showed that
better general health was associated with sleep-related complaints, regardless of age and other
The underlying mechanism linking poor SRH to a short sleep duration and quality is not
fully understood. SRH is a broad concept and likely reflects various combinations of many
potential pathways. With regard to sleep problems and negative health outcomes, several studies
have shown that sleep deprivation increases sympathetic nervous system activity, leading to
increased blood pressure and heart rate [8,9]. Sleep restriction results in metabolic and endocrine
disorders . According to Meier-Ewert et al., sleep loss may increase the cardiovascular risk
in apparently healthy individuals because of activation of inflammatory processes, which could
contribute to the association between sleep complaints and cardiovascular morbidity . The
association between poor SRH and mortality may partially be mediated by insufficient sleep
. Additionally, poor SRH may be a mediator of the associations among sleep duration,
cardiovascular disease, and mortality .
In our study, differences in the magnitude of the associations were identified because of the
method used to subdivide the sample into eight groups. This allowed us to analyze the
relationship between sleep quality and SRH, even among those with an adequate sleep duration.
Among those with an adequate sleep duration, many women reported complaints of
insufficient sleep, insomnia, or both (Table 1). The methodological procedure that we used was
beneficial compared with methods that were usually adopted in the literature, in which sleep
duration studies describe the reference category without considering sleep quality, which can
lead to an underestimation of associations. Heterogeneity in the quality of sleep among people
with an adequate sleep duration indicates the need to include aspects of sleep quality in studies
on the relationship between sleep and health.
The current study assumed that sleep problems may lead to poor SRH through, among
other factors, the influence of sleep complaints on daytime fatigue or on a decrease of
restorative sleep function . Poor health may also lead to a short sleep duration and poor quality
of sleep. Therefore, individuals with poor health are more likely to have sleep complaints and
are less able to estimate their sleep duration . Accordingly, causal conclusions cannot be
drawn from this cross-sectional study. Another limitation of this study is related to
sleep-disordered breathing, which is the second most common sleep disorder, and a potential confounder
that was not investigated. Additionally, sleep duration was based on self-reporting, which may
have involved errors, such as reflecting time in bed instead of real sleep duration . Although
measuring objective sleep duration is more accurate, this procedure is usually not feasible in
large epidemiological samples. Sleep studies based on polysomnography, the gold standard
method, or wrist activity monitoring (actigraphy)  for recording sleep could be useful for
verifying our findings. Notably, generalization of our findings should be made with caution
because nurses are a specialized group of workers who are submitted to long professional work
hours and shift work, and these aspects can influence health.
Finally, because SRH is a consistent predictor of morbidity and mortality, our results
reinforce the increasing awareness of the role of sleep in health and disease . Actually, the
clinical relevance of sleep characteristics is currently recognized by the scientific community
through maturation of the field of sleep medicine . In summary, our results contribute to
recognition of sleep as a public health problem that deserves to be better understood and
addressed by policymakers.
Conceived and designed the experiments: ASC RHG LR. Performed the experiments: ASC.
Analyzed the data: ASC. Contributed reagents/materials/analysis tools: ASC RHG LR. Wrote the
paper: ASC RHG LR.
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