Journal of Sleep Disorders: Treatment and CareISSN: 2325-9639

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Research Article, J Sleep Disord Treat Care Vol: 6 Issue: 1

Race and Gender Disparities in Sleep-Disordered Breathing

Clark KP1, Ehlen JC2 and Paul KN2*
1Department of Medicine, Morehouse School of Medicine, Atlanta, Georgia, USA
2Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, Atlanta, Georgia, USA
Corresponding author : Ketema N Paul
Department of Integrative Biology and Physiology, UCLA, Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA 90095, USA
Tel: (310)794-7755
Fax: (310)206-0484
E-mail: ketema.paul[email protected]
Received: July 10, 2016 Accepted: September 06, 2016 Published: September 13, 2016
Citation: Clark KP, Ehlen JC, Paul KN (2016) Race and Gender Disparities in Sleep-Disordered Breathing. J Sleep Disor: Treat Care 6:1. doi: 10.4172/2325-9639.1000185

Abstract

Ethnicity and race are important factors in determining risk, developing diagnostic assessments, and implementing treatment strategies for a variety of disorders. This is no less true for sleep-disordered breathing; however, there are not many epidemiological or clinical studies that include appreciable amounts of non-whites in the United States, and even fewer that make direct comparisons between races. Studies that have investigated race-related disparities in sleep-disordered breathing report that African-Americans have a higher risk for obstructive sleep apnea, particularly men, and are less likely to adhere to continuous positive airway pressure (CPAP). Here, we present a cross-sectional analysis of studies that examine racial disparities in several measures of risk, diagnosis, treatment, and outcomes of obstructive sleep apnea. These studies shed light on the complex interactions between race and the etiology of obstructive sleep apnea and underscore the need for greater inclusion of non-whites, in studies of sleep-disordered breathing.

Keywords: Obstructive sleep apnea; Sleep-disordered breathing; Ethnicity; Race; Gender; Disparities

Keywords

Obstructive sleep apnea; Sleep-disordered breathing; Ethnicity; Race; Gender; Disparities

Abbreviations

SDB: Sleep-Disordered Breathing; AA: African- American; BMI: Body Mass Index; AHI: Apnea Hypopnea Index; RDI: Respiratory Disturbance Index; ODI: Oxygen Desaturation Index; IAA: Increased Apneic Activity; PSG: Polysomnography; PCP: Primary Care Physician; HRQOL: Health-Related Quality Of Life; CPAP: Continuous Positive Airway Pressure; REM: Rapid Eye Movement; OAHI: Obstructive Apnea Hypopnea Index; SNP: Single Nucleotide Polymorphisms

Introduction

Sleep-related breathing disorders are a significant public health concern. The prevalence of obstructive sleep apnea in the United States is between 2% and 25% [1]. The 2005 National Sleep Foundation Sleep in America poll estimated one-fourth of Americans are at high risk for sleep apnea [2]. Race and ethnicity are consistently cited as risk factors for the development of sleep-disordered breathing (SDB). Most studies conducted in the United States report that African- Americans are more likely to develop SDB than other racial groups; however there have been relatively few investigations into racespecific etiologies of sleep-disordered breathing, and even fewer studies that have directly compared different ethnic groups. The few investigations of racial disparities have reported: a) under-diagnosis of sleep apnea in African-American (AA) populations, and b) AAs present with symptoms of SDB at a younger age than whites. Race has also been shown to interact with covariates such as body mass index (BMI) and socioeconomic status as predictors of health disparities in sleep-related breathing disorders. The goal of this report is to review what is known about race/ethnic differences in several aspects of obstructive sleep apnea in adult populations of both genders and to identify the gaps in understanding the role of underlying risk factors.

Epidemiology of Race and Sleep-Disordered Breathing

In a seminal investigation, Susan Redline and colleagues conducted a case-control family study to describe SDB and SDB risk factors in AAs and whites [3]. The study was conducted among 510 adult men and women who were relatives of sleep apnea patients and 337 men and women from control families in the Cleveland, Ohio area. Patients underwent overnight home sleep testing, questionnaires, and physical measurements that included cephalometry in a subset of participants with OSA. The study reported that AAs presented with SDB at a younger age than whites (37.2+/-19.5 yrs versus 45.6+/-18.7 yrs respectively). In the <25 yr group, apnea-hypopnea index (AHI), respiratory disturbance index (RDI) and increased apneic activity (IAA) prevalence was higher in AAs than whites. Racial differences in prevalence and severity of SDB were less pronounced in groups 26-55yrs and not significant among subjects >55 yrs. IAA was more common among men from all groups than women. Whites had a greater prevalence of brachycephaly and smaller middle cranial fossa length and intermaxillary length than AAs. This report was among the first to compare several measures of SDB prevalence and severity in AAs and whites across several adult age groups. It confirmed that AAs are not only more susceptible to sleep-related breathing disorders but also are more likely to become afflicted at a younger age.
More recently, Michael Friedman and colleagues conducted a prospective study to determine the incidence of obstructive sleep apnea (OSA) in AAs and whites based on subjective symptoms (screening questionnaire + Epworth Sleepiness Score) and anatomical findings (tongue position, tonsil size, BMI) [4]. The study included 287 adult AAs and 236 adult white men and women at a public health and fitness fair. This study reported that "probable" OSA was higher in AAs as was mean BMI and neck size. Additionally, this study reported acceptance of snoring is more likely in AA bed partners.
A group led by Pranathiageswaran recently examined a computerized database of 340 AA men and women and 132 white men and women in the greater Detroit, MI area with an AHI greater than 5/hr from an urban sleep center population [5]. The goal of this study was to determine the association between race and AHI. Variables in the analysis included gender, self-identified race, age, body mass index (BMI), neck circumference, and co-morbidities (hypertension, diabetes, heart disease). AA men less than 39 years and between 50-59 years had a greater AHI than white men in the same age range, even after controlling for BMI. The study also found that prevalence of hypertension was higher in AA at 46.2% compared to 12.5% for whites. Otherwise, there was no difference in co-morbidities. Heart disease, diabetes mellitus, age, and male gender were predictors of mortality in patients with AHI greater than five within the whole cohort of AA and white men and women. Baseline AHI and race were not independent predictors of mortality and there were no racial differences observed in female subjects.
While studies directly comparing sleep-disordered breathing in similar numbers of AA and white subjects have been relatively infrequent, studies conducted in primarily AA populations have been informative in understanding race-specific etiological measures. In 2008 Jean-Louis et al. [6] conducted a retrospective chart review of 421 AA patients, ages 20-80, referred by their primary care physician (PCP) for a sleep consultation. Only 160 of the patients referred (38% overall) underwent a clinical sleep consultation followed by polysomnography (PSG) [6]. Patients who adhered to their PCP recommendation for a sleep evaluation were more likely to be obese and report daytime sleepiness (multivariate-adjusted odds ratios of 2.69 [95% CI: 1.54-4.71, p<0.001] and 6.98 [95% CI: 3.86-12.64, p<0.001]). Age, sex, history of hypertension, snoring and sleep difficulty was not associated with adherence to the sleep specialist referral.
More recently the Jackson Heart Study in 2012, Fülöp et al. [7] reported a comprehensive study of an AA cohort of 5301 participants, stratified by sex and consisting of a multiple questionnaire study and exam [7]. Sleep symptoms were from five questions from the Berlin questionnaire, sleep burden, self-reported sleep duration, risk of OSA using clinical decision rule [8], global perceived stress scale, height/ weight, waist and neck girths, and the presence of hypertension, diabetes mellitus, coronary artery disease, or cerebrovascular disease. The study reported high, unadjusted prevalence rates of snoring (men 66.3% versus women 58.1%), daytime somnolence (men 68.6% versus women 61.4%), and feeling sleepy while driving (men 35.1% versus women 21.9%). Interestingly, in this population, AA women had a higher risk of OSA than men (16.8% versus 3.5%). In AA women, younger age was associated with lower prevalence of sleep symptoms and lower risk of OSA. Moreover, lower socioeconomic status (SES), being married or physically inactive was associated with greater prevalence of sleep symptoms and OSA risk in AA women, but not sleep burden. Global perceived stress and depressive symptoms in AA women had statistically significant associations with both sleep symptoms and sleep burden. In AA men, moderate to severe restless sleep was associated with odds of adverse sleep symptoms and sleep burden. Insufficient daily sleep was associated with higher odds of sleep symptoms. Taken together, these studies suggest that while some aspects of sleep-disordered breathing in AAs, such as associations with obesity and daytime sleepiness are similar to reports in primarily white populations, other aspects, such as gender differences in risk, are not.

AdherenceM

Non-adherence remains a substantial obstacle to the treatment of obstructive sleep apnea in AAs. Jean-Louis et al. [9] conducted a study of the adherence rates to referrals for sleep apnea evaluation by primary care physicians in a community sample of only AA patients [9]. In a retrospective chart review of 421 referred patients, 38% adhered to the recommendation of sleep evaluation. Of all who had the sleep evaluation, underwent a PSG. 91% of those participants received a sleep apnea diagnosis and were subsequently treated. Obesity and daytime sleepiness most accurately predicted adherence. There were no significant gender differences in the rate of diagnosis, and there were no significant associations in the severity of sleep apnea with sleep duration and BMI.
In 2011, Billings and colleagues conducted a multi-center randomized trial of home versus lab-based evaluation and treatment and assessed adherence to continuous positive airway pressure (CPAP) at one and three months [10]. At three months (when not adjusting for socioeconomic status), AA race was predictive of reduced CPAP use. CPAP adherence at three months was lower in AA subjects and subjects from lower SES (zip code). In 2012, Shaw et al. [11] reported that AAs are less likely to receive OSA evaluation and treatment than whites. The study assessed knowledge, beliefs, and attitudes towards OSA evaluation and treatment among AAs in Brooklyn, NY and it included five focus groups and employed a qualitative research design. Misconceptions about sleep apnea were common, with participants reporting that sleep apnea was a type of insomnia, an age-related phenomenon, or caused by certain bedtime activities (dietary). Barriers to OSA evaluation included unfamiliarity with the study environment, being watched while they sleep and not having a clear understanding of what the sleep assessment entails. Barriers to CPAP treatment included the confining nature of the device, discomfort wearing a mask, duration of treatment and concerns about partner's perceptions of treatment.
Billings et al. [12] in 2013, examined whether self-reported sleep measures are associated with CPAP adherence and if racial variations of the sleep characteristics explain racial differences in CPAP adherence [12]. They also conducted a secondary data analysis from a home PAP trial. AA subjects reported shorter sleep duration and longer sleep latency than white and Hispanic subjects. Shorter sleep length and longer sleep latency predicted worse CPAP adherence. Sleep duration mediated the association AAs with lower CPAP adherence over three months (insomnia symptoms were not associated with race). Shorter sleep duration among AAs was associated with longer sleep latency while African-American race and longer sleep latency were predictors of the proportion of lower sleep duration with CPAP use. Sleep measures at baseline differed by demographic. AA subjects reported shorter baseline sleep duration than whites and Hispanics. Long sleep latency was more common among AA subjects and women subjects with only a high school education or less.

Racial Differences in Advancing Age

In 1995, Ancoli-Israel et al. [13] examined the relationship between age, SDB, and race [13]. Subjects 65 years of age or older, 346 whites and 54 AAs, were studied using a portable polysomnographylike apparatus. AAs reported more sleep disturbances (more difficulty falling asleep, less sleep satisfaction, and more morning headaches) than whites. AAs were also objectively sleepier (took more naps) than whites. There was no difference in prevalence of SDB among AAs and whites; however, AAs had a higher prevalence of severe SDB. In 2000, Stepnowsky et al. [14] examined if AAs were at an equal or increased risk for sleep apnea and the relationship between sleep apnea and health-related quality of life (HRQOL). A portable polysomnographylike apparatus was used to measure sleep over two nights, separated by no more than seven days, in 70 AA subjects over age 65. Men had more awakenings and wake after sleep onset than women, although women had higher BMIs than men. There was a decrease in HRQOL for AAs with mild sleep apnea. Subjects with moderate-severe sleep apnea had low HRQOL in all groups. The sleep duration for women was less than men.
In 2002, Sonia Ancoli-Israel et al. [15] conducted a prospective study with a convenience sample (subjects' homes) to determine if non-dipping in older AA and white subjects is independent of, or related to, the presence of SDB. 30 AA men, 30 white men, 40 AA women, 40 white women all with complaints of snoring and excessive daytime sleepiness participated. The mean age of AA group was 73.6 years, and the mean age of the white group was 73.3 years. 46% of the AAs and 45% of whites had hypertension in this study. Two (2) nights of sleep were recorded in subjects' homes using portable sleep systems. Complete blood pressure and sleep data were available in 61 AAs and 63 whites. AAs had a higher dipping ratio; therefore, were non-dippers, at night regardless of respiratory disturbance index (RDI), oxygen desaturation index (ODI), body mass index, or mean arterial pressure compared with whites. The dipping ratio was greater in SDB patients with hypertension in both races. Men had higher RDIs than women. Men prescribed antihypertensive medication had higher RDIs than men not prescribed antihypertensive medication. Women prescribed antihypertensive medication had lower RDIs than women not prescribed antihypertensive medication. Higher RDIs were correlated with non-dipping only in AAs receiving antihypertensive medication (R2 = 0.0373). These studies demonstrate that even within the older population race and gender affects subjective and objective sleep disturbances, quality of life as well as the prevalence of severe OSA.

Comorbidities

The co-relationships of sleep-disordered breathing and comorbid diseases also exhibit race disparities. For instance, in 2013, Olafiranye et al. [16] reviewed the current literature on OSA, cardiovascular disease correlation and ethnic/racial differences in this association. AAs had a higher rate of both OSA and cardiovascular disease compared with whites. Patients with OSA had higher rates of hypertension, coronary heart disease, arrhythmia, stroke, and heart failure than subjects without OSA. The authors emphasized the need for more studies in AA populations. In 2005, Jean-Louis et al. [17] revealed that the severity of SDB was highest in AA hypertensive patients with family histories of hypertension, and Sands-Lincoln et al. [18] in 2013 reported the association of OSA and hypertensive status by race/ethnicity. Again, the limited number of AAs included in these studies makes it difficult to draw larger conclusions about race.
In 2009, Mahmood et al. [19] reported that ethnic differences in the prevalence of diabetes in OSA patients might be linked to rapid eye movement (REM)-related OSA. In a sample of 1008 Hispanics, patients with REM AHI greater than ten were considered to have REM-related OSA. Subjects with OSA had an increased odds ratio of having type II diabetes, though non-significant when confounding variables were removed. Middle-aged OSA patients had higher ORs (2.8) for diabetes compared to younger OSA patients. Patients with REM-related OSA had an OR of 2.0 for diabetes; however, OSA was not independently associated with diabetes in AA or Hispanic populations.
Redline et al. [20], examined roles of race and gender in the association of obstructive apnea-hypopnea index (OAHI) with ischemic stroke. Patients untreated for OSA were longitudinally monitored for ischemic stroke. Men had a positive association of OAHI and ischemic stroke. The adjusted hazard ratio for stroke was 2.86 (95% confidence interval 1.1-7.4) in men with OAHI >19. In men with OAHI of 5 - 25, each one unit increase in OAHI was estimated to increase stroke risk by 6%. In women, stroke was associated with OAHI at levels greater than 25. This study concluded that moderate or severe OSA increases the risk of stroke in men and women, particularly in AA women. This study was important because it revealed a combined role of race and gender in the risk for stroke in apnea patients.

Genetics of Race and SDB

Genetic studies have revealed valuable information about race/ ethnic differences in OSA. In 2002, Buxbaum et al. [21] conducted a critical study, which consisted of a segregation analysis of AHI (≥ 20) and BMI phenotypes that were examined in AA and white families. AHI levels were higher in AA families than in white families. The study also reported that recessive mode of transmission is most likely for AHI and BMI in both AA and white families. In 2004, Palmer et al. [22] reported that two separate single nucleotide polymorphisms (SNP) in the Endothelian-1 (EDN-1) gene were suggestive of association with OSA in whites and AAs. AA subjects from the Cleveland Family Study were isolated to identify susceptibility loci for OSA. Linkage analysis was performed for AHI and BMI. One candidate region, with a logarithm of odds above 1, was found on chromosome 8q24 was linked with AHI. Shared and unshared genetic factors were found to be associated with OSA and obesity.
In 2012, Patel et al. [23] used the NHLBI's Candidate Gene Association Resource to identify moderate to severe sleep apnea susceptibly loci and identified novel genetic loci in patients in the Cleveland Family Study and the two Sleep Heart Health study cohorts [23]. AAs and whites were compared. For AAs, on chromosome 2, one SNP, downstream of the PLEK gene, was associated with the OSA phenotype. For whites, a SNP located in an intronic region of the PTGER3 gene, which codes for the prostaglandin E2 receptor, was associated with the OSA phenotype. Novel SNPs associated with OSA were found in genes associated with inflammation.

Conclusions

Race has a substantial impact on several measures of SDB that are informative about risk, progression, diagnosis and treatment. While race is not a discrete biological variable (most of the subjects in the studies reviewed in this article self-identified their race), biology, particularly genetics, is a major contributor to racial identity. Therefore, understanding the origins of racial disparities as they relate to sleep breathing disorders may yield clues on more effective ways to prevent and treat them. When taken together, studies that examined SDB suggest that AAs have higher risks for SDB, increased risk for severe SDB, are more likely to have comorbid conditions and are less liable to adhere to treatment. These studies also provide evidence that gender differences in SDB in AA clinical populations are different from those in primarily white clinical populations. As the general population becomes more diverse, these trends need to be considered when designing diagnostic assessments and treatment regimens for patients. Moreover, descriptions of racial disparities become more relevant as the potential to discover genetic origins of SDB risk becomes more feasible. Therefore, increasing the numbers of AAs and other racial and ethnic demographics in studies of obstructive sleep apnea will go a long way toward reducing their negative impact on public health and society in general.

Authors’ Contributions

All authors contributed to the writing of the manuscript. All authors read and approved the final manuscript.

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