Population-based epidemiologic studies have uncovered the high prevalence and wide severity spectrum of undiagnosed obstructive sleep apnea, and have consistently found that even mild obstructive sleep apnea is associated with significant morbidity. Evidence from methodologically strong cohort studies indicates that undiagnosed obstructive sleep apnea, with or without symptoms, is independently associated with increased likelihood of hypertension, cardiovascular disease, stroke, daytime sleepiness, motor vehicle accidents, and diminished quality of life. Strategies to decrease the high prevalence and associated morbidity of obstructive sleep apnea are critically needed. The reduction or elimination of risk factors through public health initiatives with clinical support holds promise. Potentially modifiable risk factors considered in this review include overweight and obesity, alcohol, smoking, nasal congestion, and estrogen depletion in menopause. Data suggest that obstructive sleep apnea is associated with all these factors, but at present the only intervention strategy supported with adequate evidence is weight loss. A focus on weight control is especially important given the expanding epidemic of overweight and obesity in the United States. Primary care providers will be central to clinical approaches for addressing the burden and the development of cost-effective case-finding strategies and feasible treatment for mild obstructive sleep apnea warrants high priority.

Epidemiology of obstructive sleep apnea: a population health perspective.

Background:
Sleep-disordered breathing (SDB) is a treatable but markedly under-diagnosed condition of frequent breathing pauses during sleep. SDB is linked to incident cardiovascular disease, stroke, and other morbidity. However, the risk of mortality with untreated SDB, determined by polysomnography screening, in the general population has not been established.

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Sleep disordered breathing and mortality: eighteen-year follow-up of the Wisconsin sleep cohort.

Background: Sleep-disordered breathing is a common condition associated with adverse health outcomes including hypertension and cardiovascular disease. The overall objective of this study was to determine whether sleep-disordered breathing and its sequelae of intermittent hypoxemia and recurrent arousals are associated with mortality in a community sample of adults aged 40 years or older. Methods and Findings: We prospectively examined whether sleep-disordered breathing was associated with an increased risk of death from any cause in 6,441 men and women participating in the Sleep Heart Health Study. Sleep-disordered breathing was assessed with the apnea–hypopnea index (AHI) based on an in-home polysomnogram. Survival analysis and proportional hazards regression models were used to calculate hazard ratios for mortality after adjusting for age, sex, race, smoking status, body mass index, and prevalent medical conditions. The average follow-up period for the cohort was 8.2 y during which 1,047 participants (587 men and 460 women) died. Compared to those without sleep-disordered breathing (AHI: ,5 events/h), the fully adjusted hazard ratios for all-cause mortality in those with mild (AHI: 5.0–14.9 events/h), moderate (AHI: 15.0–29.9 events/h), and severe (AHI: $30.0 events/h) sleep-disordered breathing were 0.93 (95% CI: 0.80– 1.08), 1.17 (95% CI: 0.97–1.42), and 1.46 (95% CI: 1.14–1.86), respectively. Stratified analyses by sex and age showed that the increased risk of death associated with severe sleep-disordered breathing was statistically significant in men aged 40–70 y (hazard ratio: 2.09; 95% CI: 1.31–3.33). Measures of sleep-related intermittent hypoxemia, but not sleep fragmentation, were independently associated with all-cause mortality. Coronary artery disease–related mortality associated with sleepdisordered breathing showed a pattern of association similar to all-cause mortality. Conclusions: Sleep-disordered breathing is associated with all-cause mortality and specifically that due to coronary artery disease, particularly in men aged 40–70 y with severe sleep-disordered breathing. Please see later in the article for the Editors’ Summary.

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Sleep-disordered breathing and mortality: A prospective cohort study

Clinic-based studies suggest that sleep-disordered breathing (SDB) is associated with glucose intolerance and insulin resistance. However, in the available studies, researchers have not rigorously controlled for confounding variables to assess the independent relation between SDB and impaired glucose metabolism. The objective of this study was to determine whether SDB was associated with glucose intolerance and insulin resistance among community-dwelling subjects (n=2,656) participating in the Sleep Heart Health Study (1994-1999). SDB was characterized with the respiratory disturbance index and measurements of oxygen saturation during sleep. Fasting and 2-hour glucose levels measured during an oral glucose tolerance test were used to assess glycemic status. Relative to subjects with a respiratory disturbance index of less than 5.0 events/hour (the reference category), subjects with mild SDB (5.0-14.9 events/hour) and moderate to severe SDB (> or =15 events/hour) had adjusted odds ratios of 1.27 (95% confidence interval: 0.98, 1.64) and 1.46 (95% confidence interval: 1.09, 1.97), respectively, for fasting glucose intolerance (p for trend < 0.01). Sleep-related hypoxemia was also associated with glucose intolerance independently of age, gender, body mass index, and waist circumference. The results of this study suggest that SDB is independently associated with glucose intolerance and insulin resistance and may lead to type 2 diabetes mellitus.

Sleep-Disordered Breathing, Glucose Intolerance, and Insulin Resistance The Sleep Heart Health Study

These are the final results of a survey of sleep-disordered breathing, which examined objective and subjective information from a large randomly selected elderly sample. We randomly selected 427 elderly people aged 65 yr and over in the city of San Diego, California. Twenty-four percent had an apnea index, AI, greater than or equal to 5 and 62% had a respiratory disturbance index, RDI, greater than or equal to 10. Correlates of sleep-disordered breathing included high relative weight and reports of snoring, breathing cessation at night, nocturnal wandering or confusion, daytime sleepiness and depression. Body mass index, falling asleep at inappropriate times, male gender, no alcohol within 2 hr of bedtime and napping were the best predictors of sleep-disordered breathing. Despite statistical significance, all of the associations between interview variables and apnea indices were small. No combination of demographic variables and symptoms allowed highly reliable prediction of AI or RDI.

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Sleep-disordered breathing in community-dwelling elderly.

Sleep apnea is characterized by transient hypoxemias which are thought to affect mental functioning. Accordingly, speculation and research have focussed on relationships between sleep apnea and dementia. We studied 235 nursing home (ie institutionalized) patients (152 women with a median age of 83.5; 83 men with a median age of 79.7) with portable sleep recording equipment. The Mattis Dementia Rating Scale and the Geriatric Depression Scale were given to each. Seventy percent of the patients had five or more respiratory disturbances per hour of sleep and 96 percent showed some dementia. Sleep apnea was significantly correlated with all subscales on the dementia rating scale. There were trivial differences in dementia ratings between those with mild-moderate apnea and those with no apnea. There were significant differences, however, between the latter two groups and those with severe apnea. In particular, items reflecting attention, initiation and perseveration, conceptualization, and memory tasks on the DRS distinguished between those with and without severe sleep apnea. Among those patients with no depression, all patients with severe sleep apnea were also severely demented. Our data suggest that there is a strong relationship between dementia and sleep apnea when the sleep apnea and dementia are severe. Although causality cannot be inferred from associations, our hypothesis for study is that sleep apnea causes deficits in brain function, possibly due to global effects rather than any particular cortical or subcortical structure.

Dementia in institutionalized elderly : relation to sleep apnea

Sleep Apnea in Female Patients in a Nursing Home: Increased Risk of Mortality

Sleep-activity patterns were objectively recorded over a 24-hr period in 19 elderly nursing home residents. On average, both sleep and wake times were observed during every hour of the 24 recorded hours; however, the sleep pattern of the residents was fragmented so that they rarely experienced even a single hour of consolidated time spent sleeping. It is hypothesized that several independent factors, including compensation for lost sleep, increased total time in bed, weakening of social constraints, and deterioration of the circadian sleep-wake rhythm, are interacting to produce this increase in sleep fragmentation.

Twenty-four-hour sleep-wake patterns in a nursing home population.

Mild sleep disordered breathing is very common in the elderly, but little is known about the course of the disorder over time. Twenty-four elderly people from a population-based study were recorded three times over an 8.5-year period. There were no significant changes in either apnea index or in respiratory disturbance index (RDI) over time, even when controlled for body mass index. For most subjects, there was great variability over time in the number of respiratory disturbances. The sensitivity of RDI > or = 15 at visit 1 predicting RDI > or = 15 at visit 3 was only 20%. The predictive value was 50%. Sleep disordered breathing measured at a single point in time is rather weakly predictive of the severity of breathing disorder 4-8 years later.

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Natural History of Sleep Disordered Breathing in Community Dwelling Elderly

Although the description of sleep-disordered breathing (SDB) appeared as far back as 1877 (Lavie, 1984), clinicians first began recognizing it as a serious problem only some thirty years ago (Guilleminault and Dement, 1978) SDB is described as respiratory cessation (apnea) or a decrease in the amplitude of respiration (hypopnea) during sleep Clinically, there are often hundreds of apneas and hypopneas seen during the night, accompanied by drops in oxygen saturation levels The apneas and hypopneas are followed by brief arousals (awakenings) that allow respiration to resume Given this pattern, many clinical patients are unable to sleep and breathe at the same time

Linda Parker

Papers

Dementia in institutionalized elderly : relation to sleep apnea

Sleep Apnea in Female Patients in a Nursing Home: Increased Risk of Mortality

Twenty-four-hour sleep-wake patterns in a nursing home population.

Natural History of Sleep Disordered Breathing in Community Dwelling Elderly

Sleep-Disordered Breathing Preliminary Natural History and Mortality Results