The diurnal blood pressure profile. A population study

Association of sleep duration and insomnia with metabolic syndrome and its components in the Women's Health Initiative

BACKGROUND

Epidemiological evidence suggests that inadequate sleep duration and insomnia may be associated with increased risk of metabolic syndrome (MetS). However, longitudinal data with repeated measures of sleep duration and insomnia and of MetS are limited. We examined the association of sleep duration and insomnia with MetS and its components using longitudinal data from the Women's Health Initiative (WHI).

METHODS

The study included postmenopausal women (ages 50-79 years) diabetes-free at enrollment in the WHI, with baseline data on sleep duration (n = 5,159), insomnia (n = 5,063), MetS, and its components. Repeated measures of self-reported sleep duration and insomnia were available from years 1 or 3 of follow-up and of the MetS components from years 3, 6 and 9. Associations were assessed using logistic regression and generalized estimating equations models, and odds ratios and 95% confidence intervals (CI) adjusted for major risk factors were calculated.

RESULTS

In cross-sectional analysis, baseline sleep duration ≥ 9 h was positively associated with MetS (OR = 1.51; 95%CI 1.12-2.04), while sleep duration of 8- < 9 h was associated with waist circumference > 88 cm and triglycerides ≥ 150 mg/dL (OR = 1.18; 95%CI 1.01-1.40 and OR = 1.23; 95%CI 1.05-1.46, respectively). Insomnia had a borderline positive association with MetS (OR = 1.14; 95%CI 0.99-1.31), and significant positive associations with waist circumference > 88 cm and glucose ≥ 100 mg/dL (OR = 1.18; 95%CI 1.03-1.34 and OR = 1.17; 95%CI 1.02-1.35, respectively). In the longitudinal analysis, change from restful sleep to insomnia over time was associated with increased odds of developing MetS (OR = 1.40; 95%CI 1.01-1.94), and of a triglyceride level ≥ 150 mg/dL (OR = 1.48; 95%CI 1.08-2.03).

CONCLUSIONS

Among postmenopausal women in the WHI, sleep duration and insomnia were associated with current and future risk of MetS and some of its components.

Obstructive sleep apnea and ambulatory blood pressure monitoring: current evidence and research gaps

Obstructive Sleep Apnea (OSA) is a common condition characterized by intermittent collapse of the upper airway during sleep, resulting in partial (hypopnoeas) and total obstructions (apneas). These respiratory events observed in OSA may trigger multiple pathways involved in the blood pressure (BP) instability during the night and potentially influencing daytime BP as well (carry-over effects). This review provides an update about the impact of OSA and its treatments on 24-h BP control. Overall, there is growing evidence suggest that OSA is associated with higher frequency of nondipping BP pattern and nocturnal hypertension in a dose-dependent manner. The presence of nondiping BP (especially the reverse pattern) is independently associated with OSA regardless of sleep-related symptoms suggesting a potential tool for screening OSA in patients with clinical indication for performing ABPM. Beyond dipping BP, preliminary evidence associated OSA with white-coat effect and higher frequency of masked hypertension and BP variability than the control group (no OSA). Unfortunately, most of the evidence on the evidence addressing the impact of OSA treatment on BP was limited to office measurements. In the last years, data from observational and randomized studies pointed that CPAP is able to promote 24-h BP decrease especially in patients with resistant and refractory hypertension. A randomized trial suggests that CPAP is able to decrease the rate of masked hypertension as compared to no treatment in patients with severe OSA. Interestingly, nondipping BP is a good predictor of BP response to CPAP making ABPM an interesting tool for better OSA management.

Reproducibility study of nocturnal blood pressure dipping in patients with high cardiovascular risk

It has been shown that in most people there is a physiological reduction in blood pressure during nighttime sleep, it falling by approximately 10% compared to daytime values (dippers). On the other hand, in some people, there is no nighttime reduction (non‐dippers). Various studies have found an association between being a non‐dipper and a higher risk of cardiovascular disease, but few have assessed whether the nocturnal pattern is maintained over time. From the database of the TAHPS study, data were available on 225 patients, each of whom underwent 24‐hour ambulatory blood pressure monitoring (ABPM) on four occasions over a period of 5 months. We studied the reproducibility of the nocturnal BP dipping pattern with mixed linear analysis and also calculated the concordance in the classification of patients as dippers or non‐dippers. The intraclass correlation coefficients between the different ABPM recordings were 0.482 and 0.467 for systolic and diastolic blood pressure, respectively. Two‐thirds (67%) and 70% of the patients classified, respectively, as dippers or non‐dippers based on systolic and diastolic blood pressure readings in the first ABPM recording were found to have the same classification based on the subsequent recordings. We conclude that the reproducibility of nocturnal dipping patterns and concordance of dipper vs non‐dipper status in individual patients is modest and therefore that we should be cautious about recommending treatments or interventions based on these patterns.

Acute inorganic nitrate supplementation and the hypoxic ventilatory response in patients with obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) have increased cardiovascular disease risk largely attributable to hypertension. Heightened peripheral chemoreflex sensitivity (i.e., exaggerated responsiveness to hypoxia) facilitates hypertension in these patients. Nitric oxide blunts the peripheral chemoreflex, and patients with OSA have reduced nitric oxide bioavailability. We therefore investigated the dose-dependent effects of acute inorganic nitrate supplementation (beetroot juice), an exogenous nitric oxide source, on blood pressure and cardiopulmonary responses to hypoxia in patients with OSA using a randomized, double-blind, placebo-controlled crossover design. Fourteen patients with OSA (53 ± 10 yr, 29.2 ± 5.8 kg/m², apnea-hypopnea index = 17.8 ± 8.1, 43%F) completed three visits. Resting brachial blood pressure and cardiopulmonary responses to inspiratory hypoxia were measured before, and 2 h after, acute inorganic nitrate supplementation [∼0.10 mmol (placebo), 4.03 mmol (low dose), and 8.06 mmol (high dose)]. Placebo increased neither plasma [nitrate] (30 ± 52 to 52 ± 23 μM, P = 0.26) nor [nitrite] (266 ± 153 to 277 ± 164 nM, P = 0.21); however, both increased following low (29 ± 17 to 175 ± 42 μM, 220 ± 137 to 514 ± 352 nM) and high doses (26 ± 11 to 292 ± 90 μM, 248 ± 155 to 738 ± 427 nM, respectively, P < 0.01 for all). Following placebo, systolic blood pressure increased (120 ± 9 to 128 ± 10 mmHg, P < 0.05), whereas no changes were observed following low (121 ± 11 to 123 ± 8 mmHg, P = 0.19) or high doses (124 ± 13 to 124 ± 9 mmHg, P = 0.96). The peak ventilatory response to hypoxia increased following placebo (3.1 ± 1.2 to 4.4 ± 2.6 L/min, P < 0.01) but not low (4.4 ± 2.4 to 5.4 ± 3.4 L/min, P = 0.11) or high doses (4.3 ± 2.3 to 4.8 ± 2.7 L/min, P = 0.42). Inorganic nitrate did not change the heart rate responses to hypoxia (beverage-by-time P = 0.64). Acute inorganic nitrate supplementation appears to blunt an early-morning rise in systolic blood pressure potentially through suppression of peripheral chemoreflex sensitivity in patients with OSA.NEW & NOTEWORTHY The present study is the first to examine the acute effects of inorganic nitrate supplementation on resting blood pressure and cardiopulmonary responses to hypoxia (e.g., peripheral chemoreflex sensitivity) in patients with obstructive sleep apnea (OSA). Our data indicate inorganic nitrate supplementation attenuates an early-morning rise in systolic blood pressure potentially attributable to blunted peripheral chemoreflex sensitivity. These data show proof-of-concept that inorganic nitrate supplementation could reduce the risk of cardiovascular disease in patients with OSA.

Lifestyle interventions for the prevention and treatment of hypertension

Hypertension affects approximately one third of the world's adult population and is a major cause of premature death despite considerable advances in pharmacological treatments. Growing evidence supports the use of lifestyle interventions for the prevention and adjuvant treatment of hypertension. In this Review, we provide a summary of the epidemiological research supporting the preventive and antihypertensive effects of major lifestyle interventions (regular physical exercise, body weight management and healthy dietary patterns), as well as other less traditional recommendations such as stress management and the promotion of adequate sleep patterns coupled with circadian entrainment. We also discuss the physiological mechanisms underlying the beneficial effects of these lifestyle interventions on hypertension, which include not only the prevention of traditional risk factors (such as obesity and insulin resistance) and improvements in vascular health through an improved redox and inflammatory status, but also reduced sympathetic overactivation and non-traditional mechanisms such as increased secretion of myokines.

The Association of Obstructive Sleep Apnea and Hypertension

Obstructive sleep apnea (OSA) is a condition characterized by recurrent episodes of partial or complete upper airway obstruction during sleep. Hypertension (HTN) is defined by the presence of a chronic elevation of systemic arterial pressure above a certain threshold value (≥140 mm Hg systolic or ≥90 mm Hg diastolic). On the surface, OSA and HTN appear very different from one another. Despite this, they share several common risk factors including obesity, male gender, and advancing age. In 2003, the Seventh Joint National Committee (JNC VII) recognized OSA as a secondary cause of HTN. As physicians, our goal is to understand the OSA-HTN association better through academic study regarding its epidemiology, its pathophysiology, and its treatment. 

Considering Circadian Pattern of Blood Pressure in the Treatment of Hypertension via Chronotherapy: A Conducive or Maladroit Approach

Medical chronobiology deals with the way body's rhythm influences a person's health and disease states. To match body rhythms, deliberate alteration of drug concentration is done to optimize therapeutic outcomes and minimize size effects and this approach is known as Chronotherapeutics. In general the concept of homeostasis has been the base for the treatment of diseases. Little importance has been given in understanding biologic rhythms and their underlying mechanisms. Designing of cardiovascular drug is done to achieve a constant or near-constant effect throughout the 24-hour with the prescribed dose. However in many cases, medication requirement during night and day time are not the same. Body rhythms may have profound effect on the treatment outcomes. It is a wrongful approach to assume that a drug dosed in the morning or evening will have the same antihypertensive effect. The vast literature record of circadian variations in Blood Pressure (BP), heart rate, hormone secretion, and platelet aggregation are examples of the impact of chronobiology. In this study we analyze the effect of circadian pattern of blood pressure on action of various antihypertensives and investigate the perspective of chronotherapeutics- whether it is a fruitful approach and rationalize its utility in the treatment of hypertension.

Evaluation of the 24-hour intraocular pressure and systemic blood pressure at the same time

PURPOSE

To obtain simultaneous 24-hour contact lens voltage and systemic arterial blood pressure values with the Sensimed Triggerfish system and Holter monitoring device.

METHODS

Ten primary open-angle glaucoma (POAG) and 8 pseudoexfoliation glaucoma (PXG) patients were included in the study. The Sensimed Triggerfish contact lens device was used to calculate the 24-hour IOP, and a Holter sphygmomanometer device was used for simultaneous 24-hour blood pressure measurements. We define the 8:00 am-11:00 pm period measurements as diurnal values and the other measurements as nocturnal values.

RESULTS

The mean nocturnal systolic values (nocturnal SBP 120.5±3.4 for POAG and 122.8±5.3mmHg for PXG) and diastolic BP (nocturnal DBP 70.2±1.9 for POAG and 68.1±1.2mmHg for PXG) were lower than the diurnal (diurnal SBP 134.6±5.3 for POAG, 145.9±41.7mmHg for PXG, diurnal DBP 79.4±5.8 for POAG and 78.6±5.1mmHg for PXG) values, and these differences were statistically significant in both groups (P=0.001 in DBP in PXG and P<0.001 for other values). In addition, nocturnal CL voltage values (228.8±41.1 for POAG and 214.3±47.0mVEq for PXG) were higher than the diurnal values (55.8±77.2 for POAG and 145.9±41.7mVEq for PXG) in the POAG and PXG groups, and these were statistically significant as well (P<0.001 for all). In the POAG and PXG groups, CL voltage had a statistically significant negative correlation with systolic (respectively, r: -0.248, P=0.001 and r: -0.272, P˂0.001) and diastolic (respectively, r: -0.115, P=0.036 and r: -0.160, P=0.028) BP values.

CONCLUSION

We observed that CL voltage values rose during the nocturnal period, with a concomitant decrease in systolic and diastolic BP.

Short sleep duration is related to kidney-related biomarkers, but not lipid profile and diet quality in diabetic nephropathy patients

Objectives: Diabetic nephropathy may adversely influence on sleep duration. The quality of diet may also be affected by both sleep duration and diabetes nephropathy. Therefore, lower diet quality in short sleepers-diabetic nephropathy patients might be related to higher metabolic abnormalities. In the present study, we investigated if sleep duration is related to diet quality indices and biochemical markers in diabetic nephropathy patients. Method: This cross-sectional study was conducted among 237 diabetic nephropathy patients, randomly selected from patients attending in the Alzahra University Hospital, Isfahan, Iran. Usual dietary intake was assessed using validated food frequency questionnaire. Diet quality indices (including diet diversity score, dietary energy density, mean adequacy ratio, and nutrient adequacy ratio) were calculated based on standard definitions. Sleep duration was estimated using self-reported nocturnal hours of sleep. Results: Short sleepers (5-6 h) had higher blood urea nitrogen and creatinine compared with those who slept more than 7.5 h (20.26 + 0.23 mg/dl vs. 17.61 + 0.30 mg/dl, P < 0.0001, and 1.98 + 0.27 mg/dl vs. 1.90 + 0.24 mg/dl, P = 0.03, respectively). Serum triglyceride levels were positively correlated with sleep duration (P = 0.02). Diet quality indices were not significantly associated with sleep duration. Conclusion: Higher sleep duration is significantly related to lower kidney-related biomarkers in diabetic nephropathy patients. Diet quality indices were not associated with sleep duration in diabetic nephropathy patients. More longitudinal studies are required to evaluate the associations of sleep duration, diet quality and biochemical markers in diabetic nephropathy patients.

Blood Pressure Variability and Autonomic Dysfunction

PURPOSE OF REVIEW

This review considers the relationship between abnormal blood pressure (BP) variability and autonomic dysfunction through an attempt to answer questions about its clinical relevance and pertinence to diabetes and cardiovascular autonomic neuropathy (CAN) and which therapeutic measures can lessen its cardiovascular impact.

RECENT FINDINGS

Office, ambulatory, and home BP monitoring identify posture-related, circadian, short-term, and long-term BP variabilities. Abnormal BP variability is a risk marker for organ damage, mortality, and cardiovascular events. Moreover, BP variability changes are common in diabetes and associated with CAN and possibly exacerbated by comorbidities like nephropathy, obstructive sleep apnoea syndrome, and chronic pain. The prognostic role of nondipping and reverse dipping is well documented in diabetes. Some findings suggest the possibility of restoring dipping with the dosage time of antihypertensive agents. Diabetes is a favorable scenario for altered BP variability, which might mediate the harmful effects of CAN. Preliminary data suggest the protective effect of targeting BP variability. However, further longitudinal outcome studies are needed. In the meantime, BP variability measures and practical expedients in antihypertensive treatment should be implemented in diabetes.

Review of and Updates on Hypertension in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a prevalent sleep disorder as is hypertension (HTN) in the 21st century with the rising incidence of obesity. Numerous studies have shown a strong association of OSA with cardiovascular morbidity and mortality. There is overwhelming evidence supporting the relationship between OSA and hypertension (HTN). The pathophysiology of HTN in OSA is complex and dependent on various factors such as sympathetic tone, renin-angiotensin-aldosterone system, endothelial dysfunction, and altered baroreceptor reflexes. The treatment of OSA is multifactorial ranging from CPAP to oral appliances to lifestyle modifications to antihypertensive drugs. OSA and HTN both need prompt diagnosis and treatment to help address the growing cardiovascular morbidity and mortality due to these two entities.

Dipping in Ambulatory Blood Pressure Monitoring Correlates With Overnight Urinary Excretion of Catecholamines and Sodium

Nondipping blood pressure (BP) is associated with increased morbidity and mortality. This study examines the relationship of "dipping" in 24-hour ambulatory BP monitoring (ABPM) with awake and sleeping urinary norepinephrine (NE) and epinephrine (EPI), and that of urinary NE and EPI with urinary sodium (UNa). Fifty nondippers and 65 dippers were included in the present study. Collected data included age, sex, body mass index, history of hypertension, current antihypertensive treatment, ABPM data, and NE, EPI, and UNa values. Hierarchical multiple regression analysis with the night-to-day ratio (NDR) of systolic BP as a dependent variable showed that the composite term of the NDRs of urinary NE and EPI was a significant predictor for dipping. Results also show a differential role of NE and EPI in circadian UNa excretion in dippers and nondippers. These results indicate that the sympathetic nervous system is involved in the regulation of circadian BP variations and UNa excretion.

The Association between Primary Open-Angle Glaucoma and Blood Pressure: Two Aspects of Hypertension and Hypotension

Glaucoma is the second leading cause of blindness worldwide. Although the mechanism of the development of primary open-angle glaucoma (POAG) is not fully understood, elevated intraocular pressure (IOP) is considered the most important risk factor. Several vascular factors have also been identified as risk factors and can lead to hypoperfusion of the optic nerve head and thus may play an important role in the pathogenesis and progression of POAG. The results of the present study suggest that both high and low blood pressure (BP) are associated with an increased risk of POAG based on a comprehensive literature review. Elevated BP is associated with elevated IOP, leading to increased risk of glaucoma, but excessive BP lowering in glaucoma patients may cause a drop in ocular perfusion pressure (OPP) and subsequent ischemic injury. The relationship between IOP, OPP, and BP suggests that the relationship between BP and glaucoma progression is U-shaped.

Relationship between Duration of Sleep and Hypertension in Adults: A Meta-Analysis

OBJECTIVES

Epidemiologic studies have shown that chronic short sleep may be associated with the development of hypertension; however, the results are controversial. This meta-analysis was conducted to determine whether the duration of sleep is associated with hypertension.

METHODS

Reference databases (PubMed, EmBase, the Cochrane Library, Chinese Biological Medicine database) were searched for studies related to sleep duration and hypertension. Sleep duration categories (≤ 5 h, 6 h, 7 h, 8 h, ≥ 9 h) and prevalence or incidence of hypertension in each sleep category were extracted. A general analysis and subgroup analyses stratified by gender, age, study design, and different definitions of sleep duration were conducted to evaluate the relationship between sleep duration and hypertension.

RESULTS

Thirteen articles out of a total of 1,628 articles involving 347,759 participants met the inclusion criteria. A U-shaped change in pooled odds ratios (ORs) for hypertension due to the change of sleep duration was observed. The unadjusted OR for hypertension of individuals who slept ≤ 5 h vs. 7 h was 1.61, 95% CI = 1.28-2.02; those who slept ≥ 9 h vs. 7 h was 1.29, 95% CI = 0.97-1.71. The pooled ORs were still significant after adjusted by age and gender. Women deprived of sleep (sleep time ≤ 5 h vs. 7 h, OR = 1.68, 95% CI = 1.39-2.03) had a higher risk of hypertension than men (OR = 1.30, 95% CI = 0.93-1.83).

CONCLUSION

Excessively longer and shorter periods of sleep may both be risk factors for high blood pressure; these associations are stronger in women than men.

A review of evidence for the link between sleep duration and hypertension

There are lines of evidence from experimental sleep deprivation studies, population-based epidemiological studies, and an interventional study that point to the potential efficacy of adequate quality sleep to prevent and treat hypertension. Experimental sleep restriction has been shown to raise blood pressure and heart rate. Insufficient sleep on a chronic basis can raise average 24-hour blood pressure and lead to structural adaptations that entrain the cardiovascular system to operate at an elevated blood pressure equilibrium and increase the risk for hypertension. Disruptions in the timing and duration of sleep could also disrupt circadian rhythmicity and autonomic balance, which can increase the prevalence of the nondipping pattern, disturb diurnal rhythm of cardiac output, and increase blood pressure variability. Short sleep duration has been found to be associated with higher blood pressure and hypertension in both cross-sectional and longitudinal epidemiological studies. The association appears stronger in middle-aged adults and in women. Experimental sleep extension has been shown to significantly reduce blood pressure in individuals with prehypertension or stage 1 hypertension. The observed association between sleep duration and hypertension raises the hypothesis that interventions to extend sleep and improve sleep quality could serve as effective primary, secondary, and tertiary preventive measures for hypertension.

A reverse dipping pattern predicts cardiovascular mortality in a clinical cohort

An abnormal dipping pattern in ambulatory blood pressure monitoring (ABPM) is a cardiovascular (CV) risk factor. However, its impact on CV mortality has not been investigated sufficiently in clinical practice to be considered a standard parameter. We assessed the association between abnormal dipping patterns and increased CV mortality in a tertiary hospital in Korea. Our retrospective cohort study included 401 patients who underwent ABPM between 1994 and 1996 in Hanyang University Hospital, Seoul, Korea. The patients were classified as risers (<0% drop in systolic BP; n=107), and others included dippers and non-dippers (≥0% drop, n=294). The follow-up period was 120 months. The frequency of CV mortality was 14.0% in risers and 5.8% in others. A Cox regression analysis found a significant association between dipping pattern and CV mortality, after adjusting for age, gender, body mass index, hypertension, diabetes mellitus, smoking and hypercholesterolemia. Risers were at greater risk of CV death than others (RR, 3.02, P=0.022), but there was no difference in event rates between dippers and non-dippers. The reverse dipping pattern may be more frequent in clinical settings than in the population at large, and it is strongly associated with increased risk of CV mortality in Korea.

Sleep duration and risk for hypertension in women: results from the nurses' health study

BACKGROUND

Acute sleep restriction has been shown to increase blood pressure and sympathetic nervous system activity.

METHODS

We investigated the relationships between sleep duration and hypertension among women whose sleep durations were self-reported in 1986 (n = 82,130) and 2000 (n = 71,658) in the Nurses' Health Study I (NHS-I) and in 2001 (n = 84,674) in the Nurses' Health Study II (NHS-II).

RESULTS

After controlling for multiple risk factors in logistic regression models, the prevalence of hypertension was significantly higher among women in all 3 groups who slept ≤5 hours (odds ratio = 1.19, 95% confidence interval [CI] = 1.14-1.25) per night compared with 7 hours. In prospective analyses using Cox regression shorter sleep duration of ≤5 hours per night was significantly associated with a higher incidence of hypertension only in younger women (hazard ratio [HR] =1.20, 95% CI = 1.09-1.31 for those aged <50 years; HR = 1.11, 95% CI = 1.00-1.23 for those aged 50-59 years). In both prevalent and incident analyses, results were consistent with obesity acting as a partial mediator. Results were not consistent with diabetes or hypercholesterolemia acting as mediators or with shift work, snoring, menopause, or postmenopausal hormone therapy acting as effect modifiers.

CONCLUSIONS

Sufficient sleep could represent a lifestyle practice worthy of investigation as an approach to reduce hypertension incidence and prevalence.

Intima-media thickness in patients with obstructive sleep apnea without comorbidities

Background

Obstructive sleep apnea (OSA) is associated with elevated risk of cardiovascular events. The early stages of vascular complications can be visualized by means of ultrasound. Intima-media thickness (IMT) correlates with the presence of risk factors of cardiovascular diseases such as hypertension, diabetes, tobacco smoking, or hyperlipidemia. However, little is known whether OSA itself may be the cause of IMT thickening.

Methods

The study group was composed of 28 patients (6 women, 22 men; mean age = 53.8 years, mean BMI = 27.1 kg/m², mean AHI = 22.4/h) with OSA who had no comorbidities. The control group consisted of 28 healthy subjects (6 women, 22 men; mean age = 53.9 years; mean BMI = 27.5 kg/m²). In both groups IMT was assessed in common carotid arteries with the use of ultrasonography. Additionally, in patients with OSA, pulse wave velocity, echocardiography, 24-h automated blood pressure monitoring, clinical signs and symptoms, and blood tests were performed to investigate possible correlations with IMT.

Results

Median IMT was 0.41 mm in OSA patients and 0.46 mm in the control group (p = 0.087). Echocardiography revealed left ventricle hypertrophy in 21 %, systolic disorders in 8 %, and diastolic disorders in 57 % of the patients. In a large majority of patients, pulse wave velocity was found to be normal. IMT correlated with age (r = 0.446, p = 0.017), total cholesterol (r = 0.518, p = 0.005), daytime systolic blood pressure (r = 0.422, p = 0.025), pulse pressure 24 h and daytime (r = 0.424, p = 0.027 and r = 0.449, p = 0.019), early mitral flow/atrial mitral flow (E/A) (r = −0.429, p = 0.023), and posterior wall diameter (PWD) (r = 0.417, p = 0.270).

Conclusion

In a relatively nonobese group of patients, no significant differences were found in the intima-media thickness between OSA patients without concomitant cardiovascular diseases and healthy controls. This may lead to the conclusion that IMT does not reflect increased risk of cardiovascular events in patients with isolated OSA.

24-hour intraocular pressure and ocular perfusion pressure in glaucoma

This review analyzes the currently available literature on circadian rhythms of intraocular pressure (IOP), blood pressure, and calculated ocular perfusion pressure (OPP) in patients with open-angle glaucoma. Although adequately powered, prospective trials are not available. The existing evidence suggests that high 24-hour IOP and OPP fluctuations can have detrimental effects in eyes with glaucoma. The currently emerging continuous IOP monitoring technologies may soon offer important contributions to the study of IOP rhythms. Once telemetric technologies become validated and widely available for clinical use, they may provide an important tool towards a better understanding of long- and short-term IOP fluctuations during a patient's daily routine. Important issues that need to be investigated further include the identification of appropriate surrogate measures of IOP and OPP fluctuation for patients unable to undergo 24-hour measurements, the determination of formulae that best describe the relationship between systemic blood pressure and IOP with OPP, and the exact clinical relevance of IOP and OPP fluctuation in individual patients. Despite the unanswered questions, a significant body of literature suggests that OPP assessment may be clinically relevant in a significant number of glaucoma patients.

Challenges in blood pressure measurement in patients treated with maintenance hemodialysis

The association between blood pressure and cardiovascular outcomes in patients undergoing hemodialysis remains controversial. This may relate in part to the technique and device used and the timing of the blood pressure measurement in relation to the hemodialysis procedure. Emerging evidence indicates that standardized hemodialysis unit blood pressure measurements or measurements obtained at home, either by the patient or using an ambulatory blood pressure monitor, may offer advantages over routine hemodialysis unit blood pressure measurements for determining cardiovascular risk and treatment. This review discusses the available evidence and implications for clinicians and clinical trials.

Association of sleep duration and hypertension among US adults varies by age and sex

BACKGROUND

While short sleep duration has been related to hypertension, the impact of age and sex on this association is less well known. We examined the association between hours of sleep and hypertension prevalence among US adults by age and sex.

METHODS

The study was conducted using data from the 2007-2009 National Health Interview Surveys (NHISs). The association between self-reported hours of sleep and prevalence of hypertension was assessed after stratifying by age and sex.

RESULTS

Among 71,455 participants, age-standardized hypertension prevalence rates (%) were 32.4, 25.5, 22.2, 23.2, 25.5, and 32.5 among adults reporting sleep of <6, 6, 7, 8, 9, and ≥10 h/day, respectively (P < 0.001). There was a "U"-shaped association of hours of sleep and hypertension prevalence among all age and sex subgroups. Logistic regression models, using 8 h sleep/day as the referent, showed a greater likelihood of hypertension among those who slept <7 or ≥10 h/day after adjusting for sociodemographic, behavior, and health characteristics. Further stratifying by age and sex, while adjusting for all other characteristics, revealed that among adults less than 45 years, short (<6 h for men and <8 h for women) and long (≥10 h for men) sleep were associated with higher likelihood of hypertension. For other age/sex groups, short sleep (<6 h) was associated with higher likelihood of hypertension among middle-aged men and older women, as was long sleep (≥10 h) among middle-aged women.

CONCLUSIONS

This national sample study suggests that the association between hours of sleep and hypertension varies by age and sex.

Association between habitual sleep duration and blood pressure and clinical implications: a systematic review

Elucidation of the association between short sleep duration and elevated blood pressure has implications for assessing and managing hypertension in adults.

OBJECTIVE

To assess the relationship between sleep duration and blood pressure, and its role in the etiology of hypertension.

METHODS

On a systematic search from MEDLINE, EMBASE, CINAHL, PEDro, PsychINFO and grey literature were included articles with participants over 18 years, reported sleep duration, measured blood pressure or diagnosed hypertension, and the relationship between sleep duration and blood pressure was analyzed.

RESULTS

Of 2522 articles initially identified, 11 studies met the inclusion criteria. Sample sizes ranged from 505 to 8860 (aged ≥ 20-98 years). Five studies (aged ≥ 58-60 years) determined that sleep duration and blood pressure were unrelated. In younger adults, five studies reported an association between short sleep duration and hypertension before adjustment for confounding variables; only the findings from one study remained significant after adjustment. Two studies supported a sex association; women who sleep less than 5-6 h nightly are at greater risk of developing hypertension.

CONCLUSION

Sleep duration and blood pressure are associated in both women and adults under 60 years. Controlled studies are needed to elucidate confounding factors and the degree to which sleep profiles could augment diagnosis of hypertension and sleep recommendations to prevent or manage hypertension.

Resistant hypertension and sleep apnea: pathophysiologic insights and strategic management

Resistant hypertension is common among adults with hypertension affecting up to 30% of patients. The treatment of resistant hypertension is important because suboptimal blood pressure control is the leading preventable cause of death worldwide. A frequent comorbid condition in patients with resistant hypertension is obstructive sleep apnea. The pathophysiology of sleep apnea-associated hypertension is characterized by sustained adrenergic activation and volume retention often posing treatment challenges in patients with resistant hypertension. This review will address some of the epidemiologic data associating apnea with the pathogenesis of resistant hypertension. Diagnosis and management of apnea and its associated hypertension will also be considered.

Predictive role of the nighttime blood pressure

Numerous studies addressed the predictive value of the nighttime blood pressure (BP) as captured by ambulatory monitoring. However, arbitrary cutoff limits in dichotomized analyses of continuous variables, data dredging across selected subgroups, extrapolation of cross-sectional studies to prospective outcomes, and lack of comprehensive adjustments for confounders make interpretation of the literature difficult. We reviewed prospective studies with total mortality or a composite cardiovascular end point as an outcome in relation to the level and the circadian profile of systolic BP. We analyzed studies in hypertensive patients (n = 23 856) separately from those in individuals randomly recruited from populations (n = 9641). We pooled summary statistics and individual subject data, respectively. In both patients and populations, in analyses in which nighttime BP was additionally adjusted for daytime BP and vice versa, nighttime BP was a stronger predictor than daytime BP. With adjustment for the 24-hour BP, both the night-to-day BP ratio and dipping status remained significant predictors of outcome but added little prognostic value over and beyond the 24-hour BP level. In the absence of conclusive evidence proving that nondipping is a reversible risk factor, the option whether or not to restore the diurnal blood pressure profile to a normal pattern should be left to the clinical judgment of doctors and should be individualized for each patient. Current guidelines on the interpretation of ambulatory BP recording need to be updated.

Epidemiological evidence for the links between sleep, circadian rhythms and metabolism

Epidemiological data reveal parallel trends of decreasing sleep duration and increases in metabolic disorders such as obesity, diabetes and hypertension. There is growing evidence that these trends are mechanistically related. The seasonal expression of the thrifty genotype provides a conceptual framework to connect circadian and circannual rhythms, sleep and metabolism. Experimental studies have shown sleep deprivation to decrease leptin, increase ghrelin, increase appetite, compromise insulin sensitivity and raise blood pressure. Habitually short sleep durations could lead to insulin resistance by increasing sympathetic nervous system activity, raising evening cortisol levels and decreasing cerebral glucose utilization that over time could compromise beta-cell function and lead to diabetes. Prolonged short sleep durations could lead to hypertension through raised 24-h blood pressure and increased salt retention resulting in structural adaptations and the entrainment of the cardiovascular system to operate at an elevated pressure equilibrium. Cross-sectional and longitudinal epidemiological studies have shown associations between short sleep duration and obesity, diabetes and hypertension. If metabolic changes resulting from sleep restriction function to increase body weight, insulin resistance and blood pressure then interventions designed to increase the amount and improve the quality of sleep could serve as treatments and as primary preventative measures for metabolic disorders.

24-hour variation in the reactivity of rate-pressure-product to everyday physical activity in patients attending a hypertension clinic

The exercise-related response of the rate-pressure-product (RPP) is a prognostic marker of autonomic imbalance, cardiovascular mortality, and silent myocardial ischemia in hypertension. In view of the well-known 24 h variation in out-of-hospital sudden cardiac events, our aim was to investigate whether the reactivity of RPP to everyday physical activities varies over the 24 h. Ambulatory measurements of systolic blood pressure (BP) and heart rate were recorded every 20 min for 24 h in 440 diurnally active patients attending a hypertension clinic. Wrist activity counts were summed over the 15 min that preceded a BP measurement. An RPP reactivity index was derived for each of twelve 2 h data bins by regressing the change in RPP against the change in logged activity counts. The RPP showed 24 h variation (p < 0.0005), with a peak of 11,004 (95% CI = 10,757 to 11,250) beat . min(-1) . mmHg occurring at 10:00 h (2 h after mean wake-time). The overall 24 h mean of RPP reactivity was 477 beat . min(-1) . mmHg . logged activity counts(-1) (95% CI = 426 to 529). The largest increase in RPP reactivity occurred within the first 2 h after waking (p < 0.0005). There were no subsequent significant differences in RPP reactivity up to 14 h after waking. The lowest RPP reactivity was found 18-20 h after waking, with a peak-to-trough variation of 593 beat . min(-1) . mmHg . logged activity counts(-1) (95% CI = 394 to 791, p < 0.0005). Although this variation was not moderated by BP status, age, or sex, less variability in RPP reactivity was found for the medicated individuals during the waking hours. These data suggest that under conditions of normal living, the reactivity of RPP to a given change in physical activity increases markedly during the first 2 h after waking from nocturnal sleep, the time when out-of-hospital sudden cardiac events are also most common. Therefore, these data add weight to the notion that reactivity of RPP to physical activity could be a prognostic marker of autonomic imbalance and cardiovascular mortality, although more research is needed to assess the specific prognostic value of 24 h ambulatory measurements of RPP and physical activity.

Can nocturnal hypertension predict cardiovascular risk?

Nocturnal hypertension and non-dipping of blood pressure during sleep are distinct entities that often occur together and are regarded as important harbingers of poor cardiovascular prognosis. This review addresses several aspects related to these blood pressure abnormalities including definitions, diagnostic limitations, pathogenesis and associated patient profiles, prognostic significance, and therapeutic strategies. Taken together, persistent nocturnal hypertension and non-dipping blood pressure pattern, perhaps secondary to abnormal renal sodium handling and/or altered nocturnal sympathovagal balance, are strongly associated with deaths, cardiovascular events, and progressive loss of renal function, independent of daytime and 24-hour blood pressure. Several pharmacological and non-pharmacological approaches may restore nocturnal blood pressure and circadian blood pressure rhythm to normal; however, whether this translates to a clinically meaningful reduction in unfavorable cardiovascular and renal consequences remains to be seen.

Reproducibility of home and ambulatory blood pressure in children and adolescents

OBJECTIVE

To evaluate the reproducibility of blood pressure measured at home (HBP) in comparison with ambulatory (ABP) and clinic blood pressure (CBP) in children and adolescents.

PARTICIPANTS AND METHODS

Individuals aged 8-17 years who had been referred for elevated CBP were included. CBP was measured at two visits, HBP on 5 days and ABP for 24 h. A second session including all the above measurements was performed after 8 weeks. The reproducibility of CBP (second visit of each session), HBP (average of days 2-5 of each session) and ABP (average 24-h, awake and asleep) was quantified using test-retest correlations coefficients (r) and the standard deviation of differences (SDD) between repeated measurements.

RESULTS

Sixteen individuals were included [mean age 13.3+/-2.9 (SD)] years, range 8-17, nine boys]. According to Task Force CBP criteria, eight were classified as hypertensives, three as high normal and five as normotensives. The reproducibility of HBP (systolic/diastolic r, 0.74/0.82, SDD 7.0/4.3) was superior to that of CBP (r, 0.63/0.80, SDD 10.4/6.3). However, ABP appeared to provide the most reproducible values (r, 0.87/0.84, SDD 5.5/4.3 for 24-h ABP; r, 0.85/0.76, SDD 5.9/5.0 for awake; r, 0.76/0.79, SDD 7.0/5.0 for asleep ABP). Aspects of the diurnal ABP variation were poorly reproducible (r, 0.62/0.14, SDD 6.8/5.5 for awake-asleep ABP difference; r, 0.55/0.26, SDD 0.07/0.11 for awake : asleep ratio).

CONCLUSION

These data suggest that in children and adolescents home blood pressure measurements are more reproducible than clinic measurements. However, 24-h ambulatory monitoring appears to provide the most reproducible blood pressure values.

Short sleep duration and incident coronary artery calcification

CONTEXT

Coronary artery calcification is a subclinical predictor of coronary heart disease. Recent studies have found that sleep duration is correlated with established risk factors for calcification including glucose regulation, blood pressure, sex, age, education, and body mass index.

OBJECTIVE

To determine whether objective and subjective measures of sleep duration and quality are associated with incidence of calcification over 5 years and whether calcification risk factors mediate the association.

DESIGN, SETTING, AND PARTICIPANTS

Observational cohort of home monitoring in a healthy middle-aged population of 495 participants from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort Chicago site (black and white men and women aged 35-47 years at year 15 of the study in 2000-2001 with follow-up data at year 20 in 2005-2006). Potential confounders (age, sex, race, education, apnea risk, smoking status) and mediators (lipids, blood pressure, body mass index, diabetes, inflammatory markers, alcohol consumption, depression, hostility, self-reported medical conditions) were measured at both baseline and follow-up. Sleep metrics (wrist actigraphy measured duration and fragmentation, daytime sleepiness, overall quality, self-reported duration) were examined for association with incident calcification. Participants had no detectable calcification at baseline.

MAIN OUTCOME MEASURE

Coronary artery calcification was measured by computed tomography in 2000-2001 and 2005-2006 and incidence of new calcification over that time was the primary outcome.

RESULTS

Five-year calcification incidence was 12.3% (n = 61). Longer measured sleep duration was significantly associated with reduced calcification incidence (adjusted odds ratio, 0.67 per hour [95% confidence interval, 0.49-0.91 per hour]; P = .01). No potential mediators appreciably altered the magnitude or significance of sleep (adjusted odds ratio estimates ranged from 0.64 to 0.68 per sleep hour; maximum P = .02). Alternative sleep metrics were not significantly associated with calcification.

CONCLUSION

Longer measured sleep is associated with lower calcification incidence independent of examined potential mediators and confounders.

Reproducibility of the ambulatory arterial stiffness index in hypertensive patients

BACKGROUND

We studied the repeatability of the ambulatory arterial stiffness index (AASI), which can be computed from 24-h blood pressure (BP) recordings as unity minus the regression slope of diastolic on systolic BP.

METHODS

One hundred and fifty-two hypertensive outpatients recruited in Nijmegen (mean age = 46.2 years; 76.3% with systolic and diastolic hypertension) and 145 patients enrolled in the Systolic Hypertension in Europe (Syst-Eur) trial (71.0 years) underwent 24-h BP monitoring at a median interval of 8 and 31 days, respectively. We used the repeatability coefficient, which is twice the SD of the within-participant differences between repeat recordings, and expressed it as a percentage of four times the SD of the mean of the paired measurements.

RESULTS

Mean AASI (crude or derived by time-weighted or robust regression) and 24-h pulse pressure (PP) were similar on repeat recordings in both cohorts. In Nijmegen patients, repeatability coefficients of AASI and PP were approximately 50%. In Syst-Eur trial patients, repeatability coefficient was approximately 60% for AASI and approximately 40% for PP. For comparison, repeatability coefficients for 24-h systolic and diastolic BP were approximately 30%. Differences in AASI between paired recordings were correlated with differences in the goodness of fit (r2) of the AASI regression line as well as with differences in the night-to-day BP ratio. However, in sensitivity analyses stratified for type of hypertension, r2, or dipping status, repeatability coefficients for AASI did not widely depart from 50 to 60% range.

CONCLUSION

Estimates of mean AASI were not different between repeat recordings, and repeatability coefficients were within the 50-60% range.

Post- to pre-overnight sleep systolic blood pressures are associated with sleep respiratory disturbance, pro-inflammatory state and metabolic situation in patients with sleep-disordered breathing

OBJECTIVE

The aim of the current study was to investigate whether changes in post- to pre-overnight sleep systolic blood pressure (SSBP) are associated with sleep respiratory disturbance, pro-inflammatory state, and metabolic situation in patients with sleep-disordered breathing (SDB).

METHODS

Anthropometry, sleep polysomnography, biochemical markers, and pre- and post-overnight sleep BP were measured from 263 SDB patients. All SDB patients were further subgrouped into MORNING SURGE (% changes from post- to pre-overnight SSBP >+1SD of this cohort), MORNING DROP (% changes <-1SD), CONSTANT HIGH (% changes within+/-1SD, averaged SSBP>130mmHg) and CONSTANT LOW (% changes within+/-1SD, averaged SSBP<130mmHg).

RESULTS

BMI, neck circumference, waistline circumference, respiratory disturbance index, arousal index, lowest oxygen saturation, duration of SaO(2)<90%, blood glucose, hs-CRP, and metabolic syndrome score in MORNING SURGE and CONSTANT HIGH were significantly greater than those in CONSTANT LOW. Except metabolic syndrome score, all other parameters in MORNING DROP were similar to those in CONSTANT LOW.

CONCLUSION

Patients with SDB whose post- to pre-overnight SSBPs were elevated or maintained a constant high have more sleep respiratory disturbance, more pro-inflammatory state, and higher metabolic syndrome indices than the rest. Without subdividing into CONSTANT LOW, MORNING DROP, CONSTANT HIGH, and MORNING SURGE, the important pathophysiologic points of SDB patients will possibly be missed.

Obstructive sleep apnea and hypertension

There has long been a recognized link between obstructive sleep apnea (OSA) and the cardiovascular system, no aspect of which has been more studied than blood pressure. Research in OSA has not only demonstrated dysregulation of homeostatic cardiovascular mechanisms but also has furthered our understanding of blood pressure regulatory control. Acute nocturnal blood pressure elevations associated with disordered breathing events have been reproduced from a number of observational studies, the accrual of which has also made an increasing argument for the importance of OSA in the pathogenesis of diurnal hypertension, as suggested by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), which implicated OSA as a secondary cause of hypertension. Accumulating data from randomized controlled treatment trials in OSA, particularly with continuous positive airway pressure, though sometimes inconsistent, suggest a potential role in blood pressure reduction. Further research is needed to better clarify indications for OSA treatment as well as its role as an adjunct to other antihypertensive treatments.

Cardiovascular dynamics in healthy subjects with differing heart rate responses to tilt

Orthostatic stress such as head-up tilt (HUT) elicits a wide range of heart rate (HR) and arterial pressure (AP) responses among healthy individuals. In this study, we evaluated cardiovascular dynamics in healthy subjects with different HR responses to HUT, but without autonomic dysfunction. We measured AP (brachial artery) and HR (ECG) during 5 min of 60 degrees HUT in 76 healthy normotensive individuals. We then chose individuals on the basis of the extremes of HR responses to HUT (high = DeltaHR > or = 20 beats/min, and low = DeltaHR < or = 10 beats/min; n = 15 per group). Peak HR during HUT was 87 +/- 10 beats/min in the high and 69 +/- 14 beats/min in the low group (P < 0.05). High HR responders had lower systolic pressure at baseline (121 +/- 9 vs. 129 +/- 11 mmHg, P < 0.05) and during HUT (120 +/- 10 vs. 131 +/- 13 mmHg, P < 0.05), and higher plasma norepinephrine (NE) response to HUT (DeltaNE: 156.9 +/- 17.8 vs. 89.0 +/- 17.2 pg/ml; P < 0.05). DeltaNE during HUT was also significantly correlated with DeltaHR when all 76 subjects were included in a regression analysis (r = 0.39; P < 0.001). Pulse pressure was lower during HUT in high HR responders compared with low HR responders (45 +/- 1 vs. 55 +/- 2 mmHg, P < 0.05). High HR responders also had larger fluctuations in systolic and pulse pressure during HUT (coefficient of variation = 10.7 +/- 0.7 vs. 5.7 +/- 0.3%; 7.9 +/- 0.5 vs. 4.1 +/- 0.4%, respectively, P < 0.05). Sex distribution was different between groups (high: 5 women, 10 men; low: 10 women, 5 men). Higher HR with lower AP during HUT is consistent with normal baroreflex mechanisms of integration. Although interindividual variability appears to be a fundamental part of cardiovascular regulation, the mechanisms of these differences and the sex discrepancy requires further investigation.

Different classifications of nocturnal blood pressure dipping affect the prevalence of dippers and nondippers and the relation with target-organ damage

OBJECTIVE

We assessed how different definitions of the awake and asleep periods and use of various blood pressure (BP) indices affect the extent of the nocturnal BP dip, the prevalence of dippers and nondippers, their respective reproducibilities and the relation of nondipping with target-organ damage.

METHODS

We performed 24-h ambulatory BP monitoring twice and determined the left ventricular mass index and urinary albumin excretion as indices of target-organ damage in 150 hypertensive patients (off-medication). Awake and asleep periods were assessed using fixed and diary time methods, covering all readings available (wide) or excluding morning and evening transition hours (narrow). Nondipping (BP dip < 10%) was established for systolic BP and diastolic BP, their combinations (and/or), and mean arterial pressure.

RESULTS

The different awake-asleep definitions caused significant variation in both the extent of the BP dip and the number of dippers and nondippers in comparison with the wide diary definition (i.e. use of actual awake and sleep periods). The prevalences of dippers and nondippers also varied significantly with the BP index. Reproducibility analyses of the BP dip and the dipping status yielded repeatability coefficients (expressed as percentages of nearly maximal variation) between 42.39 and 48.71%, and kappa values between 0.323 and 0.459, respectively. Some classifications, but not all, discriminated significantly between consistent dippers and nondippers in terms of left ventricular mass index or urinary albumin excretion.

CONCLUSIONS

Use of different definitions of awake-asleep and BP indices affects significantly the classification of nocturnal BP dipping and its relation with hypertensive target-organ damage.

Obstructive sleep apnea, cardiovascular disease, and pulmonary hypertension

With the growing epidemic of obesity in an aging population, obstructive sleep apnea (OSA) is increasingly encountered in clinical practice. Given the acute cardiopulmonary stressors consequent to repetitive upper airway collapse, as well as evidence for cardiovascular homeostatic dysregulation in subjects with sleep apnea, there is ample biologic plausibility that OSA imparts increased cardiovascular risk, independent of comorbid disease. Indeed, observational studies have suggested strong associations with multiple disorders, such as systemic hypertension, heart failure, cardiac arrhythmias, and pulmonary hypertension. Further data in the form of longitudinal cohort studies and randomized controlled trials are accruing to add to the body of evidence. This review examines pathophysiologic mechanisms and explores current concepts regarding the impact of OSA and its treatment on selected clinical disease states.

Reproducibility of the circadian blood pressure pattern in 24-h versus 48-h recordings: the Spanish Ambulatory Blood Pressure Monitoring Registry

OBJECTIVES

To assess the reproducibility of the circadian blood pressure (BP) pattern over a 48-h period by comparing the first 24 h of ambulatory blood pressure monitoring (ABPM) with the following 24 h and with the mean over 48 h.

PATIENTS AND METHODS

Patients undergoing 48-h ABPM within the National ABPM Registry of the Spanish Society of Hypertension, based on 800 Spacelabs 90207 monitors distributed throughout Spain in hypertension units and primary healthcare centres, were included. Between June 2004 and September 2005, 611 valid 48-h ABPM recordings were obtained, 235 corresponded to patients without antihypertensive treatment.

RESULTS

The percentages of patients classified as non-dipper for the first 24 h, the second 24 h and the 48-h average were 47, 50 and 48%, respectively. When the first and second 24-h periods were compared, 147 (24%) subjects switched from dipper (D) to non-dipper (ND) or vice-versa. When the first 24-h period was compared to the 48-h average, 66 (11%) subjects switched patterns. The proportions were similar separately for systolic blood pressure (SBP) and diastolic blood pressure (DBP) and between treated and untreated patients. In subjects with poor ABPM reproducibility, night-to-day ratios were of an intermediate value between those of subjects always classified as D or ND.

CONCLUSION

Categorization of D or ND based on a single 24-h ABPM is moderately reproducible, since one out of every five patients change profile over the following 24 h. Nevertheless, the use of 48-h ABPM in clinical practice should be assessed according to cost-effectiveness criteria. Night-to-day ratios may be helpful in identifying patients with a stable profile.

Prognostic accuracy of day versus night ambulatory blood pressure: a cohort study

BACKGROUND

Few studies have formally compared the predictive value of the blood pressure at night over and beyond the daytime value. We investigated the prognostic significance of the ambulatory blood pressure during night and day and of the night-to-day blood pressure ratio.

METHODS

We did 24-h blood pressure monitoring in 7458 people (mean age 56.8 years [SD 13.9]) enrolled in prospective population studies in Denmark, Belgium, Japan, Sweden, Uruguay, and China. We calculated multivariate-adjusted hazard ratios for daytime and night-time blood pressure and the systolic night-to-day ratio, while adjusting for cohort and cardiovascular risk factors.

FINDINGS

Median follow-up was 9.6 years (5th to 95th percentile 2.5-13.7). Adjusted for daytime blood pressure, night-time blood pressure predicted total (n=983; p<0.0001), cardiovascular (n=387; p<0.01), and non-cardiovascular (n=560; p<0.001) mortality. Conversely, adjusted for night-time blood pressure, daytime blood pressure predicted only non-cardiovascular mortality (p<0.05), with lower blood pressure levels being associated with increased risk. Both daytime and night-time blood pressure consistently predicted all cardiovascular events (n=943; p<0.05) and stroke (n=420; p<0.01). Adjusted for night-time blood pressure, daytime blood pressure lost prognostic significance only for cardiac events (n=525; p> or =0.07). Adjusted for the 24-h blood pressure, night-to-day ratio predicted mortality, but not fatal combined with non-fatal events. Antihypertensive drug treatment removed the significant association between cardiovascular events and the daytime blood pressure. Participants with systolic night-to-day ratio value of 1 or more were older, at higher risk of death, and died at an older age than those whose night-to-day ratio was normal (> or =0.80 to <0.90).

INTERPRETATION

In contrast to commonly held views, daytime blood pressure adjusted for night-time blood pressure predicts fatal combined with non-fatal cardiovascular events, except in treated patients, in whom antihypertensive drugs might reduce blood pressure during the day, but not at night. The increased mortality in patients with higher night-time than daytime blood pressure probably indicates reverse causality. Our findings support recording the ambulatory blood pressure during the whole day.

Blunted cardiovascular responses to daytime activities as related to reduced nocturnal blood pressure decline

BACKGROUND

Individuals showing less than a 10% decline in blood pressure at night ("nondippers") are known to be at increased risk for hypertension and other cardiovascular conditions.

PURPOSE

This research tested the assertion by Räikkönen et al. (1) that nondippers show blunted cardiovascular responses to activities during daytime hours.

METHODS

Ambulatory blood pressure and impedance monitoring was performed with 149 young adults in Singapore. At each daytime blood pressure reading, participants completed a computerized questionnaire indicating location, posture, physical activities, feelings, and social interactions.

RESULTS

Significant interactions between dipper status and feeling tired, location, posture, and physical activity provided qualified support for the blunting hypothesis. However, blunting of BP responses was not attributable to blunting of either cardiac output or total peripheral resistance responses.

CONCLUSION

Nondippers appear to show blunted daytime responses to certain types of daytime activities. However, these effects are limited and appear to be the result of different mechanisms than those responsible for reduced nighttime blood pressure decline.