Undiagnosed sleep-disordered breathing among male nondippers with essential hypertension

Determinants of daytime blood pressure in relation to obstructive sleep apnea in men

This study investigated the roles of different potential pathophysiological mechanisms in the determination of blood pressure in relation to obstructive sleep apnea. The study was designed as a cross-sectional study. Consecutive healthy male subjects who were to undergo polysomnography were recruited. Demographic and anthropometric data were collected. Blood pressure measurements were taken in the evening before sleep and the next morning on waking. Overnight urinary samples for catecholamines and fasting blood for cortisol, insulin, glucose, and lipids were taken. Ninety-four men were analyzed, with a mean age of 43.7 +/- 9.3 years and mean apnea-hypopnea index (AHI) of 27.5 +/- 26.2 events/h. Sixty-nine patients (73%) had obstructive sleep apnea (AHI >or= 5). Urinary catecholamines were positively correlated with severity of sleep apnea, independent of obesity. Blood pressure measurements correlated with age, obesity, severity of sleep apnea, and urinary catecholamines. Regression analysis showed that sleep indices and urinary catecholamines were independent determinants of morning systolic and diastolic blood pressure, respectively, while total cholesterol and waist circumference were respective additional factors. Urinary catecholamines and waist circumference were determinants of evening blood pressure, with morning cortisol being an additional determinant for diastolic blood pressure. Obstructive sleep apnea and related sympathetic activity contributed significantly to the determination of daytime blood pressure in overweight middle-aged men without overt cardiometabolic diseases, and other contributing factors include abdominal obesity, total cholesterol, and cortisol levels.

Do restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) play a role in nocturnal hypertension and increased cardiovascular risk of renally impaired patients?

Hypertension can cause or promote renal failure and is related to cardiovascular mortality, the major cause of death in patients with renal impairment. Changes in the circadian BP pattern, particularly the blunting or reversal of the nocturnal decline in BP, are common in chronic renal failure. These changes in turn are among the major determinants of left ventricular hypertrophy. Using a chronobiological approach, it is possible to obtain better insight into the reciprocal relationship between hypertension, renal disease, and increased cardiovascular risk of renal patients. Disruption of the normal circadian rhythm of rest/activity may be hypothesized to underlie the high cardiovascular morbidity and mortality of such patients. Epidemiological studies reveal that hemodialysis patients experience poor subjective sleep quality and insomnia and, in comparison to healthy persons, are more likely to show shorter sleep duration and lower sleep efficiency. Sleep apnea may be present and is usually investigated in these patients; however, the prevalence of restless legs syndrome (RLS), which is high in dialysis patients and which has been associated with increased risk for cardiovascular disease in the general population, could also play a role in the pathogenesis of sleep-time hypertension in renal patients. Careful assessment of sleep quality, in particular, diagnostic screening for RLS and periodic limb movements (PLM) in renal patients, is highly recommended. In renal failure, attention to sleep quality and related perturbations of the sleep/wake cycle may help prevent the occurrence and progression of cardiovascular disease.

The price of obstructive sleep apnea-hypopnea: hypertension and other ill effects

This review addresses the cardiovascular, cerebrovascular, and metabolic consequences that accompany obstructive sleep apnea-hypopnea (OSAH) in conjunction with the mechanistic pathways implicated in mediating these effects. Particular emphasis is placed on the association with hypertension (HTN). Varying levels of evidence support a role of OSAH in perpetuating sustained HTN, nocturnal HTN, and difficult to control HTN as well as in contributing to the occurrences of nondipping of blood pressure (BP) and increased BP variability. In this context, the emergence of matched designs, adjusted analyses, meta-analyses as well as longitudinal and interventional studies strengthens causal inferences drawn from older observational studies, which suffered from such limitations as confounding.

Sleep-disordered breathing: autonomic mechanisms and arrhythmias

Obstructive sleep apnea (OSA) is present in at least 2% to 4% of the general population. Central sleep apnea (CSA), though less common, is highly prevalent in patients with heart failure. Both forms of sleep apnea exert strong modulatory effects on the autonomic nervous system at night through a number of mechanisms including central respiratory-cardiac coupling in the brainstem, chemoreflex stimulation, baroreflexes, and reflexes relating to lung inflation. Arousals also contribute to the autonomic disturbance. Although sleep is normally a time when parasympathetic modulation of the heart predominates and myocardial electrical stability is enhanced, OSA and CSA disturb this quiescence, creating an autonomic profile in which both profound vagal activity leading to bradyarrhythmias, and sympatho-excitation favoring ventricular ectopy are observed. The resulting tendency toward cardiac arrhythmia may directly contribute to sudden cardiac death and premature mortality in patients with sleep apnea. Therapy consists largely of treatment with continuous positive airway pressure, which has been shown to improve autonomic profile and reduce nocturnal arrhythmias.

Nocturnal pulse wave attenuation is associated with office blood pressure in a population based cohort

OBJECTIVE AND BACKGROUND

Pulse wave amplitude (PWA) derived from the digital vascular bed has been used in sleep studies. The nocturnal attenuation of PWA has been shown to reflect sympathetic activation during sleep. We assessed the relationship between nocturnal PWA attenuation and office blood pressure (BP).

METHODS

Eighty-one subjects (46 men; age 60+/-7 years; body mass index [BMI] 28.2+/-4.3 kg/m(2); apnea hypopnea index [AHI], 25.4+/-22.6 events/h; systolic BP 137+/-15 mm Hg; diastolic BP 79+/-7 mm Hg) recruited from a population based cohort underwent simultaneous ambulatory polysomnography (PSG) and peripheral arterial tonometry (PAT) recording. Episodic attenuations of PWA derived from the pulse waveform of the PAT signal were identified and characterized. Generalized least squares regression models were used to identify the associations between median PWA attenuation (PWA.att), office BP and sleep-related disordered breathing.

RESULTS

We found that the association between PWA.att and office BP was independent of gender, age, BMI, antihypertensive medication, number of attenuation episodes, AHI, oxygen desaturation 4% index (ODI4) and arousal index. Each 10% increase in PWA.att was associated with increases of 5.0 mm Hg systolic BP (P=0.02) and 3.0 mm Hg diastolic BP (P=0.005). We also found independent relationships between systolic/diastolic BP and BMI (P=0.0006/0.001), AHI (P=0.03/0.1) and ODI4 (P=0.03/0.03).

CONCLUSIONS

The degree of PWA attenuation during the night is associated with office BP independent of sleep-disordered breathing. Continuous assessment of PWA during sleep may provide novel insights into cardiovascular physiology and morbidity.

Short sleep duration as an independent predictor of cardiovascular events in Japanese patients with hypertension

BACKGROUND

It is not known whether short duration of sleep is a predictor of future cardiovascular events in patients with hypertension.

METHODS

To test the hypothesis that short duration of sleep is independently associated with incident cardiovascular diseases (CVD), we performed ambulatory blood pressure (BP) monitoring in 1255 subjects with hypertension (mean [SD] age, 70.4 [9.9] years) and followed them for a mean period of 50 (23) months. Short sleep duration was defined as less than 7.5 hours (20th percentile). Multivariable Cox hazard models predicting CVD events were used to estimate the adjusted hazard ratio and 95% confidence interval (CI) for short sleep duration. A riser pattern was defined when mean nighttime systolic BP exceeded daytime systolic BP. The end point was a cardiovascular event: stroke, fatal or nonfatal myocardial infarction (MI), and sudden cardiac death.

RESULTS

In multivariable analyses, short duration of sleep (<7.5 hours) was associated with incident CVD (hazard ratio [HR], 1.68; 95% CI, 1.06-2.66; P = .03). A synergistic interaction was observed between short sleep duration and the riser pattern (P = .09). When subjects were classified according to their sleep time and a riser vs nonriser pattern, the group with shorter sleep duration plus the riser pattern had a substantially and significantly higher incidence of CVD than the group with predominant normal sleep duration plus the nonriser pattern (HR, 4.43; 95% CI, 2.09-9.39; P < .001), independent of covariates.

CONCLUSIONS

Short duration of sleep is associated with incident CVD risk and the combination of the riser pattern and short duration of sleep that is most strongly predictive of future CVD, independent of ambulatory BP levels. Physicians should inquire about sleep duration in the risk assessment of patients with hypertension.

Sleep apnea diagnosis using an ECG Holter device including a nasal pressure (NP) recording: validation of visual and automatic analysis of nasal pressure versus full polysomnography

BACKGROUND

New simplified techniques for diagnosing sleep apnea should be specially tailored for easy use in cardiologic practice.

OBJECTIVES

e dedicated one of the channels of a Holter Electrocardiogram (ECG) device (SpiderView() ELA Medical, France) to nasal pressure (NP) recordings. We also developed an automatic analysis of NP signal providing an apnea-hypopnea index (AHI) for physicians without the know-how in sleep medicine.

METHODS

Thirty-four unselected patients referred for symptoms suggesting sleep apnea underwent a polysomnography (PSG) with simultaneous NP and Holter ECG recordings. An expert blinded to PSG results visually scored the Holter plus NP recordings. The results of the AHI obtained in PSG (AHI-PSG) were compared, respectively, to the AHI-NP obtained by visual analysis and automatic analysis (AHI-NP Auto) of Holter ECG nasal pressure.

RESULTS

In 10 randomly selected subjects (development set), the best cut-off on Holter ECG for diagnosing sleep apnea patients as defined by AHI>20/h in PSG was determined at 35 events/h by a receiver operator curve (ROC) analysis. Prospective testing of this threshold was then performed in 19 subjects (test set). For visually scored recordings of Holter ECG plus NP, we obtained a negative predictive value (NPV) of 80% and a positive predictive value (PPV) of 100% for sleep apnea. The area under the ROC curve was 0.97. For the automatic analysis, the NPV was 86% and the PPV value 100%. The area under the ROC curve was 0.85.

CONCLUSIONS

NP recording using a Holter system is an efficient and easy-to-use tool for screening for sleep-disordered breathing in routine cardiology practice.

Ambulatory blood pressure monitoring: a versatile tool for evaluating and managing hypertension in children

In recent years, pediatric practitioners have increasingly used ambulatory blood pressure (ABP) monitoring for evaluating blood pressure (BP) abnormalities in children. ABP monitoring in adults is superior to casual BP measurements for predicting cardiovascular morbidity and mortality, and whereas the association with target-organ damage in children is not as definitive, early evidence does seem to parallel the adult data. In addition to confirming hypertension at diagnosis, ABP monitoring may be useful for identifying isolated nocturnal hypertension, characterizing BP patterns, and assessing response to therapeutic interventions. This article reviews current evidence supporting the use of ABP monitoring in children and discusses limitations in our understanding of this technology, specifically focusing on indications for its use and interpretation of the large quantity of data obtained by ABP monitoring.

Increased low-grade inflammation and plasminogen-activator inhibitor-1 level in nondippers with sleep apnea syndrome

OBJECTIVE

Patients with sleep apnea syndrome have an increased risk of cardiovascular events and frequently show a nondipper pattern (blunted nocturnal decline <10%) of systolic blood pressure. We investigated neurohumoral activation and risk factors in relation to nocturnal blood pressure dipping pattern and sleep apnea syndrome.

METHODS

We conducted sleep polysomnography and ambulatory blood pressure monitoring and measured high-sensitivity C-reactive protein, tissue-type plasminogen activator inhibitor-1, and neurohumoral factors in 121 outpatients with suspected sleep apnea syndrome who were classified into four groups on the basis of the presence or the absence of dipping/nondipping and sleep apnea syndrome.

RESULTS

Nondippers with sleep apnea syndrome had higher high-sensitivity C-reactive protein (overall P < 0.001), plasminogen activator inhibitor-1 (overall P = 0.004), and aldosterone levels (overall P = 0.010) than any of the other three groups. After adjustment for significant covariates such as age, sex, body mass index, waist circumference, smoking, alcohol drinking, aspirin use, presence of diabetes, and insulin, nondippers with sleep apnea syndrome still had a higher high-sensitivity C-reactive protein level than nondippers without sleep apnea syndrome (geometric mean: 1.47 vs. 0.37 mg/l, P = 0.001). In multiple linear regression analysis controlling for confounding factors related with sleep apnea syndrome, high-sensitivity C-reactive protein was significantly correlated with 3% oxygen desaturation index (P = 0.047). Plasminogen activator inhibitor-1 level was also highest in the nondippers with sleep apnea syndrome but not independent of obesity. Plasminogen activator inhibitor-1 level correlated with insulin (r = 0.32, P = 0.002) and high-sensitivity C-reactive protein levels (r = 0.26, P = 0.005).

CONCLUSION

Nondipper status was associated with an increased high-sensitivity C-reactive protein level in patients who also had sleep apnea syndrome but not in those who did not. High-sensitivity C-reactive protein level was closely affected by the desaturation level. Plasminogen activator inhibitor-1 level is also increased in nondippers with sleep apnea syndrome and is related to insulin and high-sensitivity C-reactive protein levels.

Hall M, Strollo PJ, Owens JF, Buysse DJ, Lee L, Reis SE. Blood pressure dipping and sleep disturbance in African-American and Caucasian men and women

BACKGROUND

Elevated night time/daytime blood pressure (BP) ratios are associated with cardiovascular morbidity and mortality. We evaluated the associations between sleep/awake BP ratios and sleep disturbances.

METHODS

Sleep disturbances were assessed by in-home actigraphy and diary measures for nine nights, and polysomnography (PSG) for two nights; ambulatory BP was measured for at least 48 h. Participants were 186 middle-aged African-American and Caucasian men and women who were free from prevalent myocardial infarction, stroke, history of interventional cardiology procedures, diabetes, and diagnosed apnea or other sleep disorders.

RESULTS

Results showed that the greater the sleep/wake ratios of BP, the more fragmented the sleep, the greater the proportion in stage 1 (light) sleep and the smaller the proportion in rapid eye movement (REM) sleep, and the greater the number of arousals from sleep. These results were independent of age, race, gender, Framingham Risk status, cardiovascular medications, body mass index, and apnea/hypopnea index. Indicators of psychosocial stress were not greater among those with higher sleep/wake BP ratios.

CONCLUSIONS

Findings are consistent with the hypothesis that elevated night time/daytime pressure may be a consequence of poor sleep.

Circadian variation of blood pressure: the basis for the chronotherapy of hypertension

Ambulatory blood pressure (BP) measurements present a close correlation with target organ damage and cardiovascular events, including myocardial infarction, stroke and cardiovascular mortality. With the use of this measurement technique, a significant circadian variation has been shown to characterize BP. This circadian BP variation, although affected by a variety of external factors, represents the influence of internal factors such as ethnicity, gender, autonomic nervous system tone, vasoactive hormones, and hematologic and renal variables. In most individuals, BP presents a morning increase, a small post-prandial valley, and a deeper descent during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced or even reversed. This cannot be determined by traditional clinical or home BP assessments. Subjects with a diminished nocturnal BP decline (non-dipper pattern) have a significantly worse prognosis than the ones with a normal dipper pattern. In particular, the non-dipper circadian BP pattern represents a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia and myocardial infarction. The normalization of the circadian BP pattern to a dipper profile is a novel therapeutic goal, and accumulating medical evidence suggests this can delay the progression towards the renal and cardiovascular pathology known to be a consequence of the non-dipper BP pattern. The features of the circadian BP profile have direct implications for improving the drug-delivery of antihypertensive therapies as well as the qualification of patients for medication trials and assessment.

Role of sleep-wake cycle on blood pressure circadian rhythms and hypertension

Stages of different depth characterize the temporal organization of sleep. Each stage exerts an effect on blood pressure (BP) regulation and contributes to its 24-h variation. The main determinant of the circadian influences of sleep and wakefulness on BP is the daytime sympathetic and nighttime parasympathetic prevalence, but many other physiologic mechanisms known either to induce sleep or determine arousal may play an important role in the mediation of sleep influences on BP. Alteration of one or more of such mechanisms may be reflected in altered circadian BP rhythms. Sleep- and arousal-related mechanisms and phenomena that affect circadian BP rhythms include neurohumoral sleep factors (arginine vasopressin, vasoactive intestinal peptide, somatotropin, insulin, steroid hormones and metabolites, and serotonin among others) and waking factors (corticotropin-releasing factor, adrenocorticotropin, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin (E(2))). Pathologic respiratory variations (sleep-disordered breathing) and insomnia are major causes of the sleep-related alteration of the circadian BP profile, including loss of the expected normal decline in BP by 10-20% from the daytime level. A great number of medical disorders can cause insomnia, but objective sleep studies have been performed only in a minority of them. Overall, the sleep-related pathophysiological mechanisms actually involved in causing altered circadian BP rhythms in different normotensive and hypertensive conditions are not completely understood. In any case, changes in the circadian BP rhythm are known to be strongly related to one's risk of cardiovascular morbidity and mortality, thus representing strong prognostic indicators worthy of further investigation.

Ambulatory blood pressure and cardiovascular outcome in relation to perceived sleep deprivation

Sleep deprivation induced by cuff inflations during overnight blood pressure (BP) monitoring might interfere with the prognostic significance of nighttime BP. In 2934 initially untreated hypertensive subjects, we assessed the perceived quantity of sleep during overnight BP monitoring. Overall, 58.7%, 27.7%, 9.7%, and 4.0% of subjects reported a sleep duration perceived as usual (group A), <2 hours less than usual (group B), 2 to 4 hours less than usual (group C), and >4 hours less than usual (group D). Daytime BP did not differ across the groups (all Ps not significant). Nighttime BP increased from group A to D (124/75, 126/76, 128/77, and 129/79 mm Hg, respectively; all Ps for trend <0.01). Over a median follow-up period of 7 years there were 356 major cardiovascular events and 176 all-cause deaths. Incidence of total cardiovascular events and deaths was higher in the subjects with a night/day ratio in systolic BP >10% compared with those with a greater day-night BP drop in the group with perceived sleep duration as usual or <2 hours less than usual (both P<0.01), not in the group with duration of sleep >or=2 hours less than usual (all Ps not significant). In a Cox model, the independent prognostic value of nighttime BP for total cardiovascular end points and all-cause mortality disappeared in the subjects with perceived sleep deprivation >or=2 hours. In conclusion, nighttime BP rises and loses its prognostic significance in the hypertensive subjects who perceive a sleep deprivation by >or=2 hours during overnight monitoring.

Nondipping blood pressure patterns among individuals with essential hypertension: a review of the literature

BACKGROUND

Researchers have discovered that blood pressure (BP) varies in a diurnal manner throughout a 24-hour period, being higher during the day and lower at night. Most people have a dipping BP pattern characterized by a nighttime BP that is 10-20% lower than their daytime BP. Individuals who experience a less than 10% reduction in nighttime BP are described as having a nondipping BP pattern. Although controversial, there is a growing body of evidence suggesting that a nondipping BP pattern is associated with a greater risk of target organ damage among individuals with essential hypertension.

AIM

To review the literature on the most common factors associated with nondipping BP patterns among individuals with essential hypertension.

METHODS

CINAHL (1982-March 2006), PubMed (1950-March 2006) and Cochrane Library (1966-March 2006) databases were searched using the keywords: dipper, dipping, nondipper, nondipping, ambulatory blood pressure monitoring, ABPM, hypertension, essential hypertension, high blood pressure, blood pressure, nocturnal blood pressure, nighttime blood pressure, diurnal blood pressure, and blood pressure patterns. Published studies, abstracts, dissertations as well as the reference lists of retrieved articles were reviewed. Studies were included if they involved subjects with only treated or untreated essential hypertension or those with samples of both nomotensive and treated or untreated essential hypertensive individuals. Additionally, studies needed to evaluate 24-hour, daytime and nighttime BP patterns.

RESULTS

There is some evidence to suggest advanced age, African-American ethnicity, female sex, postmenopausal status, sodium sensitivity, sleep apnea, sleep quality, anger, hostility, depression, stress, social support, and socioeconomic status have an association with nondipping BP patterns.

CONCLUSION

Knowledge of the potential factors associated with an altered nighttime BP pattern is of importance because it can help identify persons at risk for nondipping BP patterns and potential target organ damage. Furthermore, knowledge of these factors associated with a nondipping BP profile will lay the foundation for interventions to prevent/treat alterations in nighttime BP patterns.

Obstructive Sleep Apnea Syndrome

OBJECTIVES

We studied structural and functional cardiac alterations in obstructive sleep apnea (OSA), their relationship to the severity of OSA, and the effects of treatment with continuous positive airway pressure (CPAP).

BACKGROUND

Obstructive sleep apnea may influence the cardiac function by several mechanisms in the awake patient.

METHODS

Left and right ventricular morphology and function were studied using echocardiography before and after treatment with CPAP in symptomatic patients (Epworth sleepiness score, 10 +/- 4.8) with severe OSA (apnea-hypopnea index [AHI], 42 +/- 24). The patients (n = 43, 32 men) had no known cardiac disease and were obese (body mass index, 31.6 +/- 5.4 kg/m2). The same echocardiographic parameters were studied in age-matched overweight patients (n = 40; body mass index, 26.4 +/- 2.3 kg/m2).

RESULTS

The patients were hypertensive (systolic blood pressure, 153 +/- 25 mm Hg), with a higher resting heart rate (77 +/- 10 beats/min, p = 0.008) compared with age-matched control patients (n = 40). There was right ventricular dilatation, hypertrophic interventricular septum, reduced left ventricular stroke volume, tissue Doppler-determined systolic and diastolic velocities of the left and right ventricle, and normal pulmonary artery pressure. The structural and functional parameters were significantly associated with AHI (p < 0.004). Multiple stepwise regression showed the interventricular septum thickness, right ventricular free wall, and mitral annulus tissue Doppler systolic velocities to be predictive of a higher AHI (p < 0.001). Six months after treatment with CPAP, significant improvements were observed in the symptoms and hemodynamics, as well as left and right ventricular morphology and function.

CONCLUSIONS

The structural and functional consequences of OSA on the heart are influenced by the severity of AHI. These effects are reversible if the apneic episodes are abolished.

Obstructive sleep apnea and hypertension

There is growing evidence of a causal relationship between obstructive sleep apnea (OSA) and hypertension. Untreated OSA may have direct and deleterious effects on cardiovascular function and structure through several mechanisms, including sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. OSA may contribute to or augment elevated blood pressure levels in a large proportion of the hypertensive patient population. It is important to consider OSA in the differential diagnosis of hypertensive patients who are obese. OSA should be especially considered in those hypertensive patients who respond poorly to combination therapy with antihypertensive medications.

Acute Effects of Automated Continuous Positive Airway Pressure on Blood Pressure in Patients with Sleep Apnea and Hypertension

BACKGROUND

The obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by repetitive upper airway obstructions during sleep, and it might cause cardiovascular complications such as myocardial infarction, arrhythmias, and systemic and pulmonary hypertension.

OBJECTIVES

We investigated the acute effects of automatic continuous positive airway pressure (automated CPAP) on blood pressure in patients with OSAHS and hypertension.

METHODS

Polysomnography was used and ambulatory blood pressure measurements were done in 12 patients with OSAHS. Blood pressure and heart rate were measured at night (10 p.m. to 6 a.m.) and during the day (6 a.m. to 10 p.m.). During these periods systolic, diastolic and mean blood pressure and heart rate of the patients on the diagnostic day were compared with those on the treatment day.

RESULTS

Patients had moderate or severe OSAHS; their mean age was 52.8+/-4.2 years. Systolic, diastolic and mean blood pressure and heart rate between the diagnostic and treatment day were not significantly different. Standard deviations of all these parameters during the night of the treatment day (9.1+/-4.5, 7.5+/-3.3, 8.0+/-3.0 mm Hg, and 4.8+/-1.5 beats/min, respectively) were significantly lower than during the night of the diagnostic day (12.6+/-4.9 mm Hg, p=0.023, 10.8+/-3.5 mm Hg, p=0.004, 11.6+/-4.4 mm Hg, p=0.006 and 6.9+/-1.6 beats/min, p=0.003, respectively). We did not find similar results during daytime periods.

CONCLUSIONS

Automated CPAP therapy in patients with sleep apnea and hypertension did not decrease systolic and diastolic blood pressures and heart rates acutely. However, it might reduce the variability of these parameters during sleep in patients, but not during the day. It might be suggested that automated CPAP reduces cardiovascular morbidity of OSAHS via stabilizing heart rate and blood pressure during sleep.

Obstructive Sleep Apnoea, Congestive Heart Failure and Cardiovascular Disease

Sleep disordered breathing is a common condition within the general community. Mostly this is represented by obstructive sleep apnoea (OSA), a condition characterized by repetitive occlusions of the upper airway due to retro-positioning of the tongue and pharyngeal collapse during sleep. This article covers the key evidence relating OSA to both causation and progression of congestive heart failure and cardiovascular disease including hypertension. The results of recent studies are summarized, and the authors conclude that whilst progress has been made, there remain many gaps in our knowledge in relation to the contribution to the burden of cardiac disease produced by associated conditions such as OSA. Larger studies with important primary endpoints will be required to demonstrate the merit of screening and treating this disorder.

The “Nondipper” Elderly: A Clinical Entity or a Bias?

OBJECTIVES

To determine the prevalence of nondipper (ND) blood pressure profile in the elderly and to ascertain whether the ND pattern of ambulatory blood pressure in the elderly is an artifact or represents a specific clinical entity.

DESIGN

Cross-sectional, observational study.

SETTING

Cardiovascular diagnostic center, division of geriatrics, secondary care, institutional practice.

PARTICIPANTS

Sixty-five consecutive community-dwelling elderly hypertensive patients referred to the cardiovascular center.

MEASUREMENTS

The patients underwent actigraphy and ambulatory blood pressure monitoring and completed a sleep assessment questionnaire. Patients were divided based on the night-time decrease in blood pressure (>10%: "dippers" (n=19); <10%: "NDs" (n=46)).

RESULTS

Nondippers displayed poorer quality of sleep, as demonstrated objectively by actigraphic data; they obtained a higher mean score+/-standard deviation on the sleep questionnaire (4.6+/-2.9 vs 3.0+/-1.1, P=.030) and were taking more benzodiazepines (33.1% vs 10.7%, P=.035), indicating that their usual sleep quality was worse than that of dippers. Multivariate analysis showed a strong correlation between nondipper profile and quality of sleep and also with comorbidity, total number of drugs being taken, and pulse pressure.

CONCLUSION

Actigraphy demonstrates impaired sleep in the nondipper elderly. Nevertheless, the nondipping pattern seems independent of the discomfort of cuff-inflation during the night and occurs in association with higher comorbidity and polypharmacy; therefore, it cannot be considered a "bias," but is related to detrimental clinical conditions that should be studied in depth.

Daily life blood pressure changes are steeper in hypertensive than in normotensive subjects

Target organ damage in hypertensive patients is related to their increased average blood pressure and greater 24-hour blood pressure variability. Whether the rate of blood pressure changes is also greater in hypertension, producing a greater stress on arterial walls, is not known, however. Our study aimed at addressing this issue by computer analysis of 24-hour ambulatory intra-arterial blood pressure recordings in 34 subjects (29 males), 13 normotensive subjects and 21 uncomplicated hypertensive subjects (mean age+/-SD, 40.4+/-11.8 years). The number, slope (mm Hg/s), and length (beats) of systolic blood pressure ramps of 3 or more consecutive beats characterized by a progressive increase (+) or reduction (-) in systolic blood pressure of at least 1 mm Hg per beat were computed for each hour and for the whole 24-hour period. Twenty-four-hour average systolic blood pressure was 112.9+/-2.1 and 159.4+/-5.7 mm Hg in normotensive and hypertensive subjects, respectively. Over the 24 hours, the number and length of systolic blood pressure ramps were similar in both groups, whereas the slope was markedly different (24-hour mean+/-SE slope, 4.80+/-0.30 in normotensives and 6.50+/-0.40 mm Hg/s in hypertensives, P<0.05). Ramp slope was not influenced by age or reflex pulse interval changes, but it was greater for higher ramp initial systolic blood pressure values. Thus, in daily life, hypertensive subjects are characterized by steeper blood pressure changes than normotensives, and this, regardless of the mechanisms, may have clinical implications, because it may be associated with greater traumatic effect on the vessel walls of hypertensive patients.

[Cardiovascular consequences of obstructive sleep apnea syndrome]

PURPOSE

This article is an update of past and current data on the relationship between obstructive sleep apnea syndrome and cardiovascular diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Obstructive sleep apnea syndrome is a common, but under-recognised, condition and should not be considered simplistically as the association of snoring and obesity. It may be suspected by the clinical history but a definite diagnosis requires the practice of polysomnography. Numerous studies have found a significant relationship between the presence of obstructive sleep apnea syndrome and the occurrence of cardiovascular events. Nonetheless, a definite causal relationship has only been established for the occurrence of hypertension. There are multiple immediate and delayed cardiovascular responses to the apneic events and thus there are many possible physiopathological mechanisms to explain the association of obstructive sleep apnea and cardiac and vascular events, the primary one being sympathetic hyperactivity. The prognosis of obstructive sleep apnea syndrome is closely related to the incidence of cardiovascular events. FUTURE PROSPECTS AND PROJECS: The existence of an independent relationship between obstructive sleep apnea syndrome and atherosclerosis is not yet demonstrated. The beneficial effects of continuous positive airway pressure, the treatment of choice for this condition, on the incidence of cardiovascular diseases remains to be confirmed although recent studies suggest that correct treatment of obstructive sleep apnea syndrome by continuous positive airway pressure may reduce the cardiovascular risk and in particular that of hypertension.

Cardiovascular consequences of obstructive sleep apnea

Sleep apnea is associated with several cardiovascular disease conditions. A causal relationship between sleep apnea and each of these diseases is likely, but remains to be proven. The clearest evidence implicating OSA in the development of new cardiovascular disease involves data that show an increased prevalence of new hypertension in patients with OSA followed over 4 years [3]. Circumstantial evidence and data from small study samples suggest that OSA, in the setting of existing cardiovascular disease, may exacerbate symptoms and accelerate disease progression. The diagnosis of OSA always should be considered in patients with refractory heart failure, resistant hypertension, nocturnal cardiac ischemia, and nocturnal arrhythmias, especially in individuals with risk factors for sleep apnea (e.g., central obesity, age, and male gender). Treating sleep apnea may help to achieve better clinical control in these diseases and may improve long-term cardiovascular prognosis.

Relationship of systolic BP to obstructive sleep apnea in patients with heart failure

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is an independent risk factor for hypertension in the general population. Hypertension is, in turn, an important risk factor for the development and progression of congestive heart failure (CHF). Our objective was to determine whether OSA would be associated with elevated daytime BP in medically treated patients with CHF.

DESIGN

Cross-sectional study.

SETTING

Tertiary care, university-affiliated sleep disorders and heart failure clinics.

PATIENTS

Three hundred one consecutive patients with CHF.

MEASUREMENTS AND RESULTS

We measured daytime BP and performed overnight sleep studies to assess for the presence of OSA. Among these patients, OSA was present in 121 patients (40%) and their systolic BP was significantly higher than in patients without OSA. Patients with OSA were 2.89 times (95% confidence interval, 1.25 to 6.73) more likely to have systolic hypertension (ie, BP > or = 140 mm Hg) than those without OSA after controlling for other risk factors, including obesity. The degree of systolic BP elevation was directly related to the frequency of obstructive apneas and hypopneas.

CONCLUSIONS

In medically treated patients with CHF, daytime systolic BP and the prevalence of systolic hypertension are significantly increased in patients with OSA, compared to those without OSA, independent of other potentially confounding factors. OSA may therefore have contributed to the presence of systolic hypertension in some of these patients.

Sympathetic nerve activity in obstructive sleep apnoea

The mechanisms underlying the link between obstructive sleep apnoea (OSA) and cardiovascular disease are not completely established. However, there is increasing evidence that autonomic mechanisms are implicated. A number of studies have consistently shown that patients with OSA have high levels of sympathetic nerve traffic. During sleep, repetitive episodes of hypoxia, hypercapnia and obstructive apnoea act through chemoreceptor reflexes and other mechanisms to increase sympathetic drive. Remarkably, the high sympathetic drive is present even during daytime wakefulness when subjects are breathing normally and no evidence of hypoxia or chemoreflex activation is apparent. Several neural and humoral mechanisms may contribute to maintenance of higher sympathetic activity and blood pressure. These mechanisms include chemoreflex and baroreflex dysfunction, altered cardiovascular variability, vasoconstrictor effects of nocturnal endothelin release and endothelial dysfunction. Long-term continuous positive airway pressure treatment decreases muscle sympathetic nerve activity in OSA patients. The vast majority of OSA patients remain undiagnosed. Unrecognized OSA may contribute, in part, to the metabolic and cardiovascular derangements that are thought to be linked to obesity, and to the association between obesity and cardiovascular risk. Furthermore, acting through sympathetic neural mechanisms, OSA may contribute to or augment elevated levels of blood pressure in a large proportion of the hypertensive patient population.

Stroke and sleep apnoea: cause or consequence?

The relationships between obstructive sleep apnoea syndrome (OSAS) and stroke are still under discussion, but increasing evidence demonstrates that the OSAS is an independent risk factor for stroke. However, in rare cases, OSAS could be a consequence of strokes, especially if located in the brainstem. Many recent studies have found a 70 to 95% frequency of OSAS (defined by an apnoea/hypopnoea index >10) in patients with acute stroke. Age, body mass index, diabetes, and severity of stroke have been identified as independent predictors of stroke. Furthermore, the presence of OSAS in stroke patients could lead to a poor outcome. The potential mechanisms linking OSAS and stroke are probably multiple (arterial hypertension, cardiac arrhythmia, increased atherogenesis, coagulation disorders, and cerebral haemodynamic changes). Despite numerous uncertainties, OSAS should be systematically screened at the moment it is clinically suspected in patients with acute stroke. However, the optimal timing (early or differed) for treatment with nasal continuous positive airway pressure remains to be determined.

Prognostic significance of the nocturnal decline in blood pressure in individuals with and without high 24-h blood pressure: the Ohasama study

OBJECTIVE

To examine the relationship between the normal nocturnal decline in blood pressure and the risk of cardiovascular mortality in individuals with and without high 24-h blood pressure values.

METHODS

We obtained 24-h ambulatory blood pressure readings from 1542 residents of Ohasama, Japan, who were aged 40 years or more and were representative of the Japanese general population. We then followed up their survival for a mean of 9.2 years. The relationship was analysed using a Cox proportional hazards model adjusted for possible confounding factors.

RESULTS

There was a linear relationship between the nocturnal decline in blood pressure and cardiovascular mortality. On average, each 5% decrease in the decline in nocturnal systolic/diastolic blood pressure was associated with an approximately 20% greater risk of cardiovascular mortality. There were no significant interactions for the risk between 24-h systolic/diastolic blood pressure values and continuous values for the nocturnal decline in blood pressure ( for interaction 0.6). Even when 24-h blood pressure values were within the normal range ( 135/80 mmHg, average 118/69 mmHg), diminished nocturnal decreases in systolic/diastolic blood pressure were associated with an increased risk of cardiovascular mortality.

CONCLUSIONS

This is the first study to demonstrate that a diminished nocturnal decline in blood pressure is a risk factor for cardiovascular mortality, independent of the overall blood pressure load during a 24-h period, in the general population.

Increased incidence of cardiovascular disease in middle-aged men with obstructive sleep apnea: a 7-year follow-up

The incidence of a cardiovascular disease (CVD) was explored in a consecutive sleep clinic cohort of 182 middle-aged men (mean age, 46.8 +/- 9.3; range, 30-69 years in 1991) with or without obstructive sleep apnea (OSA). All subjects were free of hypertension or other CVD, pulmonary disease, diabetes mellitus, psychiatric disorder, alcohol dependency, as well as malignancy at baseline. Data were collected via the Swedish Hospital Discharge Register covering a 7-year period before December 31, 1998, as well as questionnaires. Effectiveness of OSA treatment initiated during the period as well as age, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP) at baseline, and smoking habits were controlled. The incidence of at least one CVD was observed in 22 of 60 (36.7%) cases with OSA (overnight oxygen desaturations of 30 or more) compared with in 8 of 122 (6.6%) subjects without OSA (p < 0.001). In a multiple logistic regression model, significant predictors of CVD incidence were OSA at baseline (odds ratio [OR] 4.9; 95% confidence interval [CI], 1.8-13.6) and age (OR 23.4; 95% CI, 2.7-197.5) after adjustment for BMI, SBP, and DBP at baseline. In the OSA group, CVD incidence was observed in 21 of 37 (56.8%) incompletely treated cases compared with in 1 of 15 (6.7%) efficiently treated subjects (p < 0.001). In a multiple regression analysis, efficient treatment was associated with a significant risk reduction for CVD incidence (OR 0.1; 95% CI, 0.0-0.7) after adjustment for age and SBP at baseline in the OSA subjects. We conclude that the risk of developing CVD is increased in middle-aged OSA subjects independently of age, BMI, SBP, DBP, and smoking. Furthermore, efficient treatment of OSA reduces the excess CVD risk and may be considered also in relatively mild OSA without regard to daytime sleepiness.

Sleep actigraphy in hypertensive patients with the 'non-dipper' blood pressure profile

Several prospective studies have demonstrated a higher cardiovascular complication rate in patients with a non-dipping compared with a dipping blood pressure profile. However, the extent of blood pressure reduction during sleep can be highly variable in an individual patient, and a repeat ambulatory blood pressure study commonly shows a change in category. The reasons for this variability are not clear. In general, hypertensive patients with a non-dipper blood pressure profile have higher actigraphy-measured activity during time in bed than dipper hypertensive patients but no analysis of actigraphy-determined sleep parameters has been published. We therefore prospectively studied 52 hypertensive patients who were off antihypertensive drugs for at least 3 weeks and who underwent simultaneous ambulatory and wrist actigraphy monitoring. All patients were clinically free of any sleep-related disorder. The blood pressure profile was labelled dipper when the change in mean awake blood pressure to sleep blood pressure was 10% or higher and non-dipper if less than 10%. Overall activity levels were higher during the time in bed in the non-dipper group compared with the dipper group. An inverse relationship of daytime activity with age was seen in men (r = -0.54, P = 0.001) but not in women (r = -0.06, P = 0.79). Both groups of hypertensive patients had a similar total time in bed (458 +/- 92 min, in dippers and 433 +/- 106 min in non-dippers, P = 0.39). Sleep latency (time to onset of sleep after getting into bed) was a median of 7 min in dippers and 15 min in non-dippers (P = 0.10). In addition, dipper hypertensives spent more of the time in bed asleep than non-dippers (87% vs 76%, P = 0.004). Logistic regression analysis revealed that body mass index, kg/m(2) (OR, 1.3), and night-time activity (units/min) (OR, 1.1) were predictive of a non-dipping blood pressure profile. These data show a possible disturbance of sleep in non-dipper hypertensive patients.

Sleep apnoea and hypertension

This review article provides an update on two major issues. First, the most recent evidence supporting the occurrence of an association between obstructive sleep apnoea syndrome, or more generally sleep-disordered breathing, and arterial hypertension in humans is summarized and discussed. This includes an evaluation of both cross-sectional and longitudinal studies. Second, new insights into the mechanisms responsible for the appearance of chronic hypertension in individuals suffering from recurrent nocturnal apnoeic episodes are provided, based both on experimental studies in animals and on clinical studies in humans. The relevance of these data for the clinical management of hypertensive patients with sleep-disordered breathing, and the possibility of obtaining a reduction in blood pressure through the application of nasal continuous positive air pressure, is also addressed.