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Volume 10 No. 09
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Accepted Papers





Scientific Investigations

Association of Self-Reported Sleep and Hypertension in Non-Insomniac Elderly Subjects

Emilia Sforza, M.D., Ph.D.; Magali Saint Martin, M.Sc.; Jean Claude Barthelemy, M.D., Ph.D.; Frédéric Roche, M.D., Ph.D.
Service de Physiologie Clinique et de l'Exercice, CHU Nord, Saint-Etienne, Faculté de Médecine Jacques Lisfranc, PRES de Lyon 42023, Université Jean Monnet, Saint-Etienne, France

ABSTRACT

Objectives:

Sleep duration and sleep quality play important roles in the development of hypertension (HT) in middle-aged subjects, with controversial data in elderly. In this study, we investigated the link between HT and self-reported sleep in non-insomniac elderly subjects.

Methods:

We examined 500 participants without insomnia complaints aged 72 ± 1 years. An extensive instrumental evaluation was carried out, including 24-h blood pressure (BP) monitoring and an assessment of nocturnal BP dipping. Sleep duration and quality were evaluated by the Pittsburgh Sleep Quality Index (PSQI). The subjects were stratified into three groups according to sleep duration: short (< 6 h), normal (> 6h to < 8 h), and long (> 8 h) sleepers. A PSQI < 5 defined good sleepers (GS, n = 252), and a PSQI > 5 (n = 248) defined poor sleepers (PS).

Results:

PS represented 50% of the subjects, more frequently females. Compared to GS, PS did not differ in terms of HT, BP, baroreflex sensitivity (BRS), and BP dipping. Short, normal, and long sleepers accounted for 28%, 42%, and 30% of subjects, with HT, BP values, BRS, and gender not differing between groups. No relationship was found between nocturnal BP values and self-reported sleep measures. Logistic regression analysis indicated that neither sleep duration nor sleep quality predicts the prevalence of HT, the body mass index being the only factor affecting this association.

Clinical Trial Registration:

ClinicalTrials.gov identifiers NCT00759304 and NCT00766584

Conclusions:

In a sample of non-insomniac elderly subjects, neither sleep duration nor sleep quality affected the prevalence of HT. These data argue against a relationship between self-reported sleep duration and quality and HT in elderly without insomnia.

Citation:

Sforza E, Saint Martin M, Barthelemy JC, Roche F. Association of self-reported sleep and hypertension in non-insomniac elderly subjects. J Clin Sleep Med 2014;10(9):965-971.


Several studies have shown that short sleep duration14 and insomnia57 are associated with increased blood pressure (BP) and increased risk of hypertension (HT), with greater effects being observed in women.811 In an epidemiological study on a population ranging in age from 40-100 years, Gottlieb et al. found that self-reported habitual sleep duration of less than 7 to 8 h per night was associated with an increased prevalence of HT, particularly in subjects sleeping less than 6 h per night.12 In the Penn State cohort, a sample of 1,741 subjects aged 47 to 50 years were examined by polysomnography. The authors found that subjects with poor sleep and insomnia associated with an objective sleep duration < 6 h had an increased risk of HT.6

Short sleep duration and insomnia are also associated with increased mortality1315 and morbidity.16 However, in the Gangwisch study of 4,810 participants of the NHANES cohort, a self-reported sleep duration < 5 h per night was associated with a significantly increased risk of developing HT at follow-up in middle-aged subjects, but not in subjects aged > 60 years.17

Therefore, while many epidemiological studies have suggested a relationship between sleep duration and HT in middle-aged insomnia patients, the results are conflicting in the elderly population, with some studies stressing the independent risk of short sleep for HT13,1821 and other studies finding no association.2226 The discrepancies among these reports likely stem from their incomplete control for important variables such as the definition of sleep duration by polysomnography or questionnaires,2 the type of insomnia,27 and the interference of the individual's lifestyle.

BRIEF SUMMARY

Current Knowledge/Study Rationale: An association between hyper-tension and short and poor sleep has been reported in middle-aged insomniac patients. Contradictory results have been obtained in elderly with insomnia. We assess the relationship between sleep duration and sleep quality and blood pressure values and hypertension in a large group of elderly without insomnia complaints.

Study Impact: In the elderly without insomnia, no association was found between sleep duration and sleep quality and hypertension and blood pressure values. These results argue against a true relationship between hypertension and sleep perception in older subjects.

The PROgnostic indicator OF cardiovascular and cerebrovascular events (PROOF) study28 provides an opportunity to examine the association between HT and self-reported sleep quality and duration in a larger sample of community-dwelling elderly with no insomnia complaints using a validated sleep questionnaire, i.e., the Pittsburgh Sleep Quality Index (PSQI),29 and an extensive evaluation of HT and cardiovascular function. The present study considers both sleep duration and sleep quality, a somewhat novel approach. In this way, we can assess the role not only of sleep duration but also of sleep quality on HT risk in non-insomniac older adults.

MATERIALS AND METHODS

Participants

Participants were selected from the population included in the PROOF trial, an ongoing study of the prognostic value of indicators of autonomic nervous system activity for cerebrovascular and cardiovascular morbidity and mortality.28 This group included 1,011 subjects selected between 2001 and 2003 from the population register of the city of Saint-Etienne, France, who were aged 65 ± 1.1 years at the time of inclusion. At the third clinical assessment performed between 2006 and 2009, the participants were clinically reevaluated and completed several questionnaires including an evaluation of sleep perception. The criteria for inclusion in this sub-study were (1) absence of previous myocardial infarction, stroke, dementia, and neurological or psychiatric disease; (2) no prior diagnosis of insomnia defined as difficulty to fall asleep, frequent awakenings from sleep, and/or non restorative sleep; (3) willingness to undergo 24-h blood pressure measurements and other instrumental evaluation; (4) ability to complete questionnaires; (5) French speaking; (6) no initiation of continuous positive airway pressure treatment for OSA; (7) no new diagnosis of a medical or neurological disease; and (8) residing in Saint-Etienne. Based on these criteria, complete clinical, instrumental, and questionnaire data were available for 500 subjects aged 72.0 ± 1.1 years, and this constitutes the sample of the current study (Figure 1). This sample did not differ from the overall sample at third assessment in terms of age, gender, or Epworth Sleepness Scale (ESS) and PSQI scores.

Flow chart of the inclusion procedure used to select participants.

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Figure 1

Flow chart of the inclusion procedure used to select participants.

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The PROOF study was approved by the University Hospital and the local Ethics Committee (CCPRB Rhone-Alpes Loire). The National Committee for Information and Liberty (CNIL) gave consent for data collection. All subjects gave their written consent to participate in the study.

METHODS

Questionnaires

Self-Assessment of Sleep

Self-reported sleep quality and duration were assessed by the French version of the PSQI, which has been proven to exhibit excellent sensitivity and reliability in middle-aged and elderly subjects.30,31 The PSQI questionnaire consists of 19 individual items that generate 7 component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping pills, and daytime dysfunction. According to previously published data,30 participants were divided into 2 groups: good sleepers (GS) with a score < 5 and poor sleepers (PS) with a score ≥ 5. We analyzed sleep duration as a categorical variable, and 3 groups were defined based on reported sleep duration: short sleepers who slept < 6 h, normal sleepers who slept between ≥ 6 and < 8 h, and long sleepers who slept ≥ 8 h. The cutoff values for sleep duration were chosen based on previous studies showing that sleep duration < 6 h represented short sleep,30 and that a sleep duration of approximately 7 h confers a low risk of HT.13,32

Sleepiness

The impact of sleepiness during the day was evaluated for 8 different situations using the Epworth Sleepiness Scale (ESS),33 a 4-grade scale ranging from 0 (no chance of napping) to 3 (high chance of napping). Scores > 10 were considered to indicate excessive daytime sleepiness.

Clinical and Instrumental Assessment

Clinical Assessment

Clinical characteristics were evaluated in a structured interview including history of cardiac and cerebrovascular disease, hypertension, diabetes, and respiratory, neurological, and psychiatric disorders. Current smoking, habitual alcohol consumption, and current medication were analyzed, with the medication section focusing on antihypertensive, antidiabetic, hypnotic, anxiolytic, and/or antidepressant therapy. The body mass index (BMI) was measured, calculated as weight (kg)/height squared (kg/m2), along with the neck circumference (NC), calculated at the midpoint of the neck between the mid-cervical spine and the anterior neck 0.5 cm below the laryngeal prominence. Diabetes and dyslipidemia were defined as self-reported diabetes or dyslipidemia and/or regular use of oral antidiabetics or treatment with lipid-lowering medication. No regular intake of hypnotics was reported by any participants, and 50 participants reported taking medication once to twice a week.

Instrumental Measurements of Blood Pressure and Vascular Risk Factors

Blood Pressure Assessment

Clinical systolic (SBP) and diastolic (DBP) blood pressure (BP) were measured by a physician using a standard mercury sphygmomanometer on the right arm while the subject was quietly lying down after ≥ 5 min rest. A 24-h ambulatory blood pressure monitoring (ABPM) (Diasoft, Novavor, Rueil Malmaison, France) was done to define the diurnal and nocturnal blood pressure values calculated for the time when the subject reported lying on the bed between lights off and lights on. According to standard criteria,34 subjects were defined as hypertensive if they had: clinical assessment of SBP > 140 mm Hg or DBP > 90 mm Hg; history of hypertension (HT) or anti-hypertensive treatment; or 24-h monitoring revealed a diurnal mean SBP > 135 mm Hg or a diurnal mean DBP > 85 mm Hg. Subjects were defined as dippers when their nocturnal SBP fell > 10% from daytime values.35

Measurement of Baroreflex Sensitivity (BRS)

The spontaneous cardiac baroreflex sensitivity (BRS) was calculated over 15 min at rest in the supine position.36 Finger arterial blood pressure was measured by the volume-clamp method by means of a noninvasive continuous blood pressure monitor (Finapress 2300, Ohmeda, Amsterdam, Netherlands). Spontaneous BRS was calculated using the sequence method, in which the software listed all sequences of ≥ 3 successive heart beats in which there were concordant increases and decreases in SBP and the RR interval. For each sequence, the linear regression slope was calculated. The spontaneous BRS, expressed in milliseconds per millimeter of Hg was then calculated as the mean slope of all sequences.

Statistical Analyses

Study population characteristics are reported as the mean ± SD for continuous variables, and as counts and percentages for categorical variables. Differences between groups were examined with χ2 values for categorical variables, Kruskal-Wallis tests for skewed continuous variables, and ANOVAs for normally distributed continuous variables. Pearson correlation coefficients were calculated to assess the relationship between sleep duration and quality and the various clinical and self-reported sleep parameters. A linear regression analysis was performed with diurnal and nocturnal SBP and DBP values as dependent variables; and age, total sleep time, sleep latency, sleep efficiency, BMI, and neck circumference as independent variables. A multiple logistic regression analysis was carried out with HT as the dependent variable and sleep duration and quality as the independent variables, with adjustments for potential confounding factors such as gender, diabetes, dyslipidemia, smoking, presence of sleepiness, and occasional use of hypnotics.

All statistical analyses were carried out using the SPSS statistical software package (SPSS for Windows, version 17.0, SPSS, Chicago, IL). Two-tailed p-values < 0.05 were considered to indicate statistical significance.

RESULTS

Clinical Characteristics

Table 1 presents the characteristics of the total study population. The 500 participants included in the current study had a mean age of 72.0 ± 1.1 years; 56% were women. The prevalence of HT, diabetes, and dyslipidemia were 49%, 5%, and 33%, respectively. The mean ESS was 5.7 ± 3.7, with daytime sleepiness (ESS > 10) observed in 59 subjects.

Anthropometric, biological, and vascular data of the total sample and poor and good sleepers (mean ± SD).

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Table 1

Anthropometric, biological, and vascular data of the total sample and poor and good sleepers (mean ± SD).

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Sleep Quality

The clinical data for GS and PS are reported in Table 1. Overall, the mean PSQI was 6.0 ± 3, and its median value 5.0 ± 2, with 50.4% identified as GS and 49.6% as PS, with the latter more likely to be women (p = 0.002). No significant differences were observed between GS and PS in age, anthropometric characteristics, metabolic characteristics, or smoking habits. Considering vascular parameters, no statistically significant differences were observed between groups in SBP or DBP, either at clinical evaluation or during the 24-h analysis. HT was more prevalent in the GS group (51% vs. 48%), but this difference was not statistically significant. No differences were observed between groups in nocturnal BP dipping, an indirect measure of nocturnal sympathetic activity and initial HT.

Sleep Duration

Table 2 reports the clinical, anthropometric and vascular data for the 3 groups according to self-reported sleep duration. No significant differences were observed between groups in BMI, NC, smoking, or the presence of dyslipidemia, diabetes, or sleepiness. Vascular measurements did not reveal any significant differences in diurnal or nocturnal BP values, presence/ absence of nocturnal dipping, or BRS. A tendency towards reduced BP dipping was observed in short sleepers, although this difference was not statistically significant (p = 0.07).

Anthropometric, biological, and vascular data of the three groups stratified according to sleep duration (mean ± SD).

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Table 2

Anthropometric, biological, and vascular data of the three groups stratified according to sleep duration (mean ± SD).

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The correlation analysis did not reveal any association between subjective sleep duration and quality and clinical, anthropometric, or diurnal blood pressure data. When we examined nocturnal blood pressure values, no association was found between nocturnal SBP and DBP values and reported sleep latency and sleep efficiency, the total sleep time being the only factor associated with the mean nocturnal SBP (r = -0.283, p = 0.01) and nocturnal DBP (r = -0.295, p = 0.01). Among anthropometrics variables, the SBP and DBP values were correlated with BMI (r = 0.137, p = 0.01) and neck circumference (r = 0.138, p = 0.01).

Stepwise regression analysis considering SBP and DBP during daytime and nighttime did not reveal any significant contribution of age, PSQI, ESS, and sleep variables; BMI and the neck circumference explained, respectively, 2% and 4% of the variance for diurnal and nocturnal BP values.

Multiple logistic regression analyses adjusted for gender, BMI, diabetes, dyslipidemia, sleepiness, habitual smoking, and occasional intake of hypnotics were performed to assess the contribution of categorical sleep duration and quality to the prevalence of HT (Table 3). For the categorical sleep duration and sleep quality groups, the BMI was the only key factor explaining the presence of HT (p < 0.003), with no contribution of subjective sleep quality or sleep duration.

Logistic regression analyses of the relationship between prevalence of hypertension and categorical sleep duration and sleep quality after adjustment for clinical variables

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Table 3

Logistic regression analyses of the relationship between prevalence of hypertension and categorical sleep duration and sleep quality after adjustment for clinical variables

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DISCUSSION

In this study we examined the association between self-reported sleep duration and quality, and the presence of HT in a community-dwelling elderly population with no symptoms of insomnia. Using a standardized sleep questionnaire and an extensive clinical and vascular assessment, we found that neither subjective sleep quality nor sleep duration was associated with HT and elevated BP values. After adjustments for confounding variables, the risk of HT was explained by the body weight without any contribution of self-reported sleep measurements, and with no distinction between men and women. As in insomniac elderly subjects, the lack of an association between self-reported sleep and HT might be explained by age-related changes in blood pressure control and in self-reported sleep perception in the non-insomniac elderly.

While results from epidemiological studies support the hypothesis that an objective6,7 or subjective10,13,14 short sleep duration lasting less than 5 h or less than 7 h is an environmental risk factor for HT in middle-aged subjects, the majority of studies performed in the insomniac elderly concluded that sleep duration is not associated with prevalent HT before or after adjustment for confounding variables.8,15,23,3032

In 8,757 participants in the Arteriosclerosis Risk in Communities (ARIC) study aged 45 to 69 years,29 the difficulty of falling asleep, sleep maintenance complaints, and tiredness reported at the final awakening were the most important factors predicting cardiovascular risk 6.3 years later, but they did not predict hypertension. In a recent paper on 12,643 participants with and without insomnia,33 no association was observed between objective hypertension measures and sleep duration, suggesting the lack of a true relationship in older patients. Recently, Fung and coworkers examined 853 community dwelling men aged 75 years and older participating in the Osteoporotic Fractures Men Study (MrOS), and found that total sleep time and other sleep measurements assessed by actigraphy were not associated with incident hypertension.19

In our cohort of non-insomniac elderly, we found that short sleep duration < 6 h and poor sleep quality, i.e., PSQI > 5, do not affect the presence of HT or diurnal and nocturnal BP values. Moreover, no association was found between age, nocturnal blood pressure values, and reported sleep measurements such as sleep latency and sleep efficiency, apart from subjective total sleep duration. Regression analyses found no associations between self-perceived sleep and hypertension that persisted after controlling for covariates. To explain our results, we can hypothesize that while insomnia led to HT through the hyperarousal level, a stressor state inducing activation of the sympathetic system and proinflammatory processes and endothelial dysfunction,16 in the elderly without insomnia, age-related physiological changes in sympathetic activity and nocturnal BP control37 may prevent HT occurrence. Examining baroreceptor sensitivity (an indirect marker of sympathetic activity)26 and nocturnal BP dipping (an initial marker of HT),38 we observed no significant differences in the baroreceptor sensitivity or in the decline in nocturnal BP between poor and good sleepers or between short and long sleepers. Thus, healthy elderly subjects without insomnia do not have the hyperarousal state proposed to explain the increased HT risk in insomnia patients.

Strengths and Limitations

The strengths of this study include its evaluation of a large cohort of healthy subjects who received an extensive clinical and cardiovascular assessment, allowing for a more detailed analysis of the association between vascular risk and self-reported sleep. Moreover, previous studies relying almost exclusively on a few questions on the average or monthly sleep duration and quality did not allow for a detailed analysis of self-reported sleep characteristics. We therefore decided to use the validated Pittsburgh questionnaire, which is more sensitive to sleep perception and provides information on the presence of sleep complaints and hypnotic intake.31

The first limitation of the current study is the cross-sectional design, which was not able to determine a causal relationship between self-reported sleep and hypertension. Second, the assessment of sleep duration was based on a self-report questionnaire, which provides crude estimates of objective sleep measures. However, two recent meta-analyses examining the link between sleep duration and HT showed that the majority of the studies used questionnaires that allow the analysis in a larger populations, with only three cohorts performing polysomnography.13,68 Moreover, a recent study using actigraphy to assess the prediction of HT in older men39 did not find any association between HT and objective sleep data, suggesting that the use of a detailed questionnaire may be sufficient to assess sleep perception in the elderly. Finally, no data were available on lifestyle, physical activity, and mood and anxiety disorders known to affect sleep in elderly.

CONCLUSIONS

In line with previous data in elderly insomniac subjects, the current study found no association between self-perceived sleep duration and quality and hypertension, a finding that persisted after controlling for various factors that could affect this association. Additional studies should be conducted to analyze factors other than sleep characteristics such as health status, environmental factors, and quality of life to better understand the mechanisms behind the association between perceived sleep and hypertension in older populations.

DISCLOSURE STATEMENT

This was not an industry supported study. This study was supported by a grant from the French Ministry of Health (Cellule Projet Hospitalier de Recherche Clinique National, Direction de la Recherche Clinique, CHU Saint-Etienne; Appel d'Offre 1998 and Appel d'Offre 2002), and by a grant from “L'Association de Recherche SYNAPSE” (President: Michel Segura). The authors have indicated no financial conflicts of interest.

ABBREVIATIONS

ABMP

24-h blood pressure monitoring

BMI

body mass index

BRS

baroreflex sensitivity

PS

poor sleepers

GS

good sleepers

HT

hypertension

NC

neck circumference

PSQI

Pittsburgh Sleep Quality Index

ACKNOWLEDGMENTS

The PROOF study group would like to thank all the subjects included in the present study and Mme Delphine Maudoux for her expert technical assistance.

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