Elsevier

Metabolism

Volume 64, Issue 2, February 2015, Pages 244-252
Metabolism

Excessive daytime sleepiness and metabolic syndrome: a cross-sectional study

https://doi.org/10.1016/j.metabol.2014.09.011Get rights and content

Abstract

Objective

Excessive daytime sleepiness (EDS) has been associated with singular independent symptoms of metabolic syndrome, such as insulin resistance and diabetes. The aim of this study was to assess whether this relationship is sustained among individuals who meet criteria for the whole syndrome.

Materials/methods

994 women aged 21–94 years (median 50.2 years, IQR 34–65) and 840 men aged 24–92 years (median 60.4 years, IQR 47–73) who resided in the Barwon Statistical Division, South-Eastern Australia, and participated in the Geelong Osteoporosis Study (GOS) between the years of 2001 and 2008. Anthropometric measurements, lifestyle, mood, demographic and health-related factors were obtained. Sleep duration was categorized as short (< 6 h), average (6–9 h) and long (> 9 h). Sleepiness was assessed using the Epworth Sleepiness Scale (ESS), and scores of  10 indicated EDS. The presence of metabolic syndrome was assessed using a modified version of criteria as outlined by the International Diabetics Federations recommendations (2005).

Results

Women: 138 (14.0%) of the women reported EDS; those with EDS were heavier, had a greater body mass index (BMI) and were more likely to have metabolic syndrome. The association between EDS and metabolic syndrome was sustained following adjustment for age and hours sleep (adjusted OR = 1.90, 95% CI 1.16–3.09), however BMI attenuated the relationship (adjusted OR = 1.64, 95% CI = 1.05–2.57). These findings were independent of smoking status, alcohol intake, medication use, socioeconomic status, physical activity and current diagnosis of a depressive illness. Men: 111 (13.2%) of the men reported EDS; those with EDS had a greater waist circumference and were more likely to have metabolic syndrome. Analysis of age-stratified data (< 60 years vs. ≥ 60 years) revealed that the older men with EDS were more likely to have metabolic syndrome (OR = 1.71, 95% CI 1.01–2.92), however, age explained this association (age adjusted OR = 1.51, 95% CI 0.88–2.60). In the younger age group, no association was detected between EDS and metabolic syndrome. For both men and women, the prevalence of combined EDS and metabolic syndrome increased progressively with age.

Conclusion

For women, the association between EDS and metabolic syndrome appears to be driven by adiposity measures; while for men, the association is somewhat attributed to older age. Additional research is required to assess temporal associations with underlying sleep pathology.

Introduction

Excessive daytime sleepiness (EDS) is common among adults, with recent local estimates suggesting that as many as one-third of the adult population experiences these symptoms [1]. The sleep-related disorder, obstructive sleep apnea (OSA), is the most commonly linked condition associated with EDS among both clinical [2] and population-based samples [3]. The daytime symptoms experienced by these individuals are often attributed to the degree of nocturnal impairment characteristic of the disorder, such as periods of hypoxemia or sleep fragmentation [4]. Despite this, some studies have found a poor correlation between measures of OSA disease severity and symptoms of EDS [5], [6], and have instead suggested that symptoms of EDS may be related to other factors associated with OSA, such as obesity [7]. These symptoms similarly appear associated with a number of independent factors, such as sleep restriction [6] and/or associated lifestyle, health or medical factors [1], [8].

A large body of research has highlighted the role of several health, lifestyle and disease factors in the expression of EDS, thus indicating that the mechanism of EDS exists beyond that of underlying sleep-related pathology. There is some evidence that EDS is associated with indices of increased adiposity [6], and similar research has shown that EDS can be present in the absence of underlying sleep disordered breathing among obese individuals [9], [10]. Body composition markers, in particular visceral adiposity, have previously been linked to disorders of insulin resistance and independent features of metabolic syndrome, such as type 2 diabetes and hypertension [11], [12]. In addition, several studies have demonstrated that the presence of EDS is directly associated with independent features of metabolic syndrome, such as insulin resistance [13] and diabetes [6], even after controlling for sleep disordered breathing [14]. Mechanistically, such associations may have peripheral associations with a number of inflammatory processes characteristic of metabolic disturbance [13], [15].

Characterizing the relationship between metabolic factors and EDS has several implications for overall health outcomes, not least in assisting with appropriate and effective treatment modalities for these patients. However, there is currently a paucity of information assessing the association between EDS and metabolic syndrome, particularly beyond that of individual symptom clusters. Therefore, the aim of the current study was to assess whether the observed relationship between EDS and metabolic syndrome is sustained among individuals who meet criteria for the syndrome among a large, population-based sample of adults, while assessing the relative contribution of associated lifestyle and health factors.

Section snippets

Participants

This cross-sectional study examined men and women who participated in the Geelong Osteoporosis Study (GOS). The GOS is a large, population based age-stratified cohort, located in south-eastern Australia. Participants were randomly-recruited using the Commonwealth electoral rolls for the Barwon Statistical Division (BSD) as a sampling frame.

Between the years of 1993 and1997, 1494 women were randomly recruited, representing a participation of 77.1% [10]. At the 10-year follow up (2004–2008), 881

Women

Characteristic data for women with and without EDS are presented in Table 1. 138 (14.0%) women reported EDS. The median age for female participants was 50.2 years (range 21–94 years), and no differences were detected in age between those with and without EDS. Those women who reported EDS recorded greater weight, in addition to a greater overall BMI and waist circumference than those who did not report EDS. Overall, a large proportion (68.4%) of the women met criteria for central obesity (waist

Discussion

In this large, representative and well characterized sample of Australian men and women, we assessed the association between EDS and metabolic syndrome. To our knowledge, this is the first study of its kind to assess the relationship between EDS and metabolic syndrome among a population-based sample of adults, beyond that of individual symptom clusters. We found that several lifestyle and health factors characteristic of metabolic symptoms are associated with EDS among both men and women, and

Author contributions

ACH, LJW and JAP were involved in the development and design of the study. ACH, LJW, JAP and SLB collected the data. ACH interpreted the data and wrote the manuscript. ACH, LJW, GAK, SLB, MB and JAP were involved in drafting, editing and critical appraisal of the manuscript. All authors have approved the manuscript for submission.

Declaration of conflicts of interest

ACH, GAK, SLB and JAP have no conflicts of interest, including specific financial interests and relationships and affiliations relevant to the subject matter or materials discussed in the manuscript.

MB has received Grant/Research Support from the NIH, Simons Foundation, CRC for Mental Health, Stanley Medical Research Institute, MBF, NHMRC, Beyond Blue, Geelong Medical Research Foundation, Bristol Myers Squibb, Eli Lilly, Glaxo SmithKline, Organon, Novartis, Mayne Pharma, Servier and Astra

Acknowledgments

The study was supported by grants from the NHMRC. MB is supported by an NHMRC Senior Principal Research Fellowship (1059660), LJW is supported by an NHMRC of Australia Career Development Fellowship (GNT1064272), and SLB is supported by an NHMRC of Australia Early Career Fellowship (1012472).

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