Dipping status may be determined by nocturnal urination

Sleep characteristics associated with nocturnal blood pressure nondipping in healthy individuals: a systematic review

OBJECTIVE

The current literature investigating nocturnal blood pressure (BP) nondipping has largely focused on clinical populations, however, conditions such as hypertension, obstructive sleep apnoea and insomnia are recognized confounding factors for BP dipping. The exact mechanisms responsible for BP nondipping remain unclear, therefore, there is a need to investigate BP nondipping in healthy individuals to better understand the underlying mechanisms. This review identifies sleep characteristics that may contribute to BP nondipping in healthy individuals. It is anticipated that an understanding of the sleep characteristics that contribute to BP nondipping may inform future sleep-related behavioral interventions to ultimately reducing the burden of cardiovascular disease.

METHODS

The PubMed, Scopus and Web of Science databases were searched for relevant, English language, peer-reviewed publications (from inception to March 2022). The search identified 550 studies. After duplicates were removed, the titles and abstracts of the remaining 306 studies were screened. Of these, 250 studies were excluded leaving 56 studies to test for eligibility. Thirty-nine studies were excluded such that 17 studies fully met the inclusion criteria for the review.

RESULTS

Findings from this review indicate that short sleep duration, more sleep fragmentation, less sleep depth and increased variability in sleep timing may be associated with BP nondipping in healthy individuals.

CONCLUSION

While there is no evidence-based approach for the treatment of nocturnal BP nondipping, it seems promising that addressing one's sleep health may be an important starting point to reduce the prevalence of BP nondipping and perhaps the progression to cardiovascular disease.

Bedtime dosing of antihypertensive medications: systematic review and consensus statement: International Society of Hypertension position paper endorsed by World Hypertension League and European Society of Hypertension

Antihypertensive drug therapy is one of the most efficient medical interventions for preventing disability and death globally. Most of the evidence supporting its benefits has been derived from outcome trials with morning dosing of medications. Accumulating evidence suggests an adverse prognosis associated with night-time hypertension, nondipping blood pressure (BP) profile and morning BP surge, with increased incidence of cardiovascular events during the first few morning hours. These observations provide justification for complete 24-h BP control as being the primary goal of antihypertensive treatment. Bedtime administration of antihypertensive drugs has also been proposed as a potentially more effective treatment strategy than morning administration. This Position Paper by the International Society of Hypertension reviewed the published evidence on the clinical relevance of the diurnal variation in BP and the timing of antihypertensive drug treatment, aiming to provide consensus recommendations for clinical practice. Eight published outcome hypertension studies involved bedtime dosing of antihypertensive drugs, and all had major methodological and/or other flaws and a high risk of bias in testing the impact of bedtime compared to morning treatment. Three ongoing, well designed, prospective, randomized controlled outcome trials are expected to provide high-quality data on the efficacy and safety of evening or bedtime versus morning drug dosing. Until that information is available, preferred use of bedtime drug dosing of antihypertensive drugs should not be routinely recommended in clinical practice. Complete 24-h control of BP should be targeted using readily available, long-acting antihypertensive medications as monotherapy or combinations administered in a single morning dose.

Circadian blood pressure profile and blood pressure changes following oral appliance therapy for obstructive sleep apnoea

OBJECTIVES

Oral appliance therapy for obstructive sleep apnoea (OSA) reduces blood pressure (BP) but there is little information on relationship to circadian BP pattern (nocturnal BP dipping or non-dipping). The aims of this study were to determine whether nocturnal dipping pattern influences BP changes following oral appliance therapy, and to determine the effect of oral appliance therapy on circadian BP pattern.

METHODS

Participants in two randomized trials of oral appliance therapy (1-2 months) with 24-h ambulatory BP monitoring (ABPM) data were included (N = 152). Nocturnal BP Dippers (nocturnal/diurnal SBP ratio <0.9) and non-dippers were compared for BP changes following oral appliance therapy and the effect of oral appliance therapy on nocturnal BP dipping was assessed.

RESULTS

Of 152 participants, 64.5% were dippers. Dippers were on average younger and less likely to be hypertensive (42 vs. 82.7%, P < 0.001). Nondippers showed greater reduction in nocturnal BP measures, related to higher BP measures at baseline. There was no difference in the relationship between treatment effectiveness and BP changes between groups. Oral appliance therapy converted only 23% of baseline non-dippers to a nocturnal dipping profile.

CONCLUSION

Baseline circadian BP profile influenced the BP response to oral appliance therapy, largely because of higher baseline BP in the non-dipper subgroup. Oral appliance therapy did not convert OSA patients to a more favourable circadian BP profile. Further work is required to understand the effect of oral appliance therapy on circadian BP profile and of the individuals who will receive cardiovascular benefit from oral appliance therapy.

Nocturia as an Unrecognized Symptom of Uncontrolled Hypertension in Black Men Aged 35 to 49 Years

Background

Hypertension is assumed to be asymptomatic. Yet, clinically significant nocturia (≥2 nightly voids) constitutes a putative symptom of uncontrolled hypertension. Black men with hypertension may be prone to nocturia because of blunted nocturnal blood pressure (BP) dipping, diuretic drug use for hypertension, and comorbidity that predisposes to nocturia. Here, we test the hypothesis that nocturia is a common and potentially reversible symptom of uncontrolled hypertension in black men.

Methods and Results

We determined the strength of association between nocturia (≥2 nightly voids) and high BP (≥135/85 mm Hg) by conducting in‐person health interviews and measuring BP with an automated monitor in a large community‐based sample of black men in their barbershops. Because nocturia is prevalent and steeply age‐dependent after age 50 years, we studied men aged 35 to 49 years. Among 1673 black men (mean age, 43±4 years [SD]), those with hypertension were 56% more likely than men with normotension to have nocturia after adjustment for diabetes mellitus and sleep apnea (adjusted odds ratio, 1.56; 95% CI, 1.25–1.94 [P<0.0001]). Nocturia prevalence varied by hypertension status, ranging from 24% in men with normotension to 49% in men whose hypertension was medically treated but uncontrolled. Men with untreated hypertension were 39% more likely than men with normotension to report nocturia (P=0.02), whereas men whose hypertension was treated and controlled were no more likely than men with normotension to report nocturia (P=0.69).

Conclusions

Uncontrolled hypertension was an independent determinant of clinically important nocturia in a large cross‐sectional community‐based study of non‐Hispanic black men aged 35 to 49 years.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unqiue identifier: NCT 02321618.

Nocturia and increase in nocturnal blood pressure: the Nagahama study

OBJECTIVE

Abnormalities in circadian blood pressure (BP) variation, particularly increase in nocturnal BP, have been reported to be risk factors for cardiovascular disease, although the factors associated with BP abnormalities are not fully understood. This study aimed to clarify possible associations of sleep characteristics, including sleep fragmentation, sleep disordered breathing, and nocturia, with sleep BP by simultaneous multiday measurements.

METHODS

A cross-sectional study evaluated 5959 community participants having home-measured data on nocturnal BP change (sleep BP - awaking BP), sleep characteristics, and sleep disordered breathing. Sleep characteristics including the fragmentation index were assessed using wrist-wearable actigraphy, whereas sleep disordered breathing was assessed by 3% oxygen desaturation index obtained using a finger-type monitor. The number of nocturnal urinations was recorded in a sleep diary.

RESULTS

Mean nocturnal SBP change was -8.5 ± 7.9%. A 3% oxygen desaturation index was associated with the BP change independently of the basic covariates (β = 0.051, P = 0.001), although the association became insignificant (P = 0.196) after adjusting the fragmentation index (β = 0.105, P < 0.001). The association of the fragmentation index was also insignificant (P = 0.153) after adjusting measurement season (middle season: β = 0.163, P < 0.001; summer season: β = 0.249, P < 0.001). In contrast, the frequency of urination showed strong and independent association (β = 0.140, P < 0.001), with smaller nocturnal BP drop in participants with frequent urination.

CONCLUSION

Subjective sleep estimates and frequent nocturnal urination may represent a potential risk for circadian BP abnormalities.

Nocturia: The Complex Role of the Heart, Kidneys, and Bladder

We review the role of the heart, kidneys, and bladder in the pathophysiology of nocturia and nocturnal polyuria. Lower urinary tract symptoms such as nocturia have often been associated with lower urinary tract dysfunction. It is known that the bladder contributes to nocturia in the case of low functional capacity, urgency, and detrusor overactivity. Heart diseases, especially arterial hypertension and congestive heart failure, are closely related to nocturnal polyuria. The main mechanisms include renal hyperfiltration and elevated atrial natriuretic peptide. A number of drugs frequently used in cardiovascular disorders are implicated in nocturia; diuretics, calcium channel blockers, and β-blockers induce nocturnal polyuria and thus nocturia, whereas alpha-blockers improve nocturia. Among the different forms of hypertension, nondipping arterial hypertension has been associated with a higher risk of nocturnal polyuria. Besides the role of the kidneys in nocturia linked to arterial hypertension, chronic kidney disease is an independent predictor of nocturia through an osmotic diuresis mechanism. Some evidence suggests a close relationship between the heart (nondipping arterial hypertension), kidneys (chronic kidney disease), and nocturia/nocturnal polyuria. These complex interactions between the heart, kidneys, and bladder warrant a multidisciplinary approach in patients with nocturia. PATIENT SUMMARY: We review the different mechanisms that lead to nocturia and nocturnal polyuria. The complex interactions between the heart, the kidneys, and the bladder warrant a multidisciplinary approach in patients with nocturia. Careful investigation of the cause of nocturia can improve its management.

Associations Between Characteristics of Obstructive Sleep Apnea and Nocturnal Blood Pressure Surge

Research suggests that oxygen desaturation and sleep stage during obstructive sleep apnea (OSA) are related to the magnitude of high blood pressure (BP) in a laboratory setting. However, in a clinical setting, these associations have not been well studied. We used a noninvasive oscillometric BP measurement device to investigate the association between oxygen-triggered BP levels at the end of each OSA episode and the characteristics of the preceding OSA episode. In 42 newly diagnosed OSA patients (average age, 63.5±12.5 years; average apnea-hypopnea index, 32.6±18.2 per hour), 258 BP measurements were obtained at the end of OSA episodes. Hypoxia-peak systolic BP (SBP), defined as the maximum oxygen-triggered SBP value, was significantly higher in rapid eye movement sleep (144.9±19.9 mm Hg) than in non-rapid eye movement stage 1 sleep (129.5±15.1 mm Hg; P<0.001) and non-rapid eye movement stage 2 sleep (129.4±14.7 mm Hg; P<0.001). In a multivariate-linear mixed model, the lowest oxygen saturation percentage during each OSA episode was associated with increased hypoxia-peak SBP (-0.501 mm Hg; P<0.001), nocturnal SBP surge (-0.395 mm Hg; P<0.001), defined as the difference between the hypoxia-peak SBP and the mean nocturnal SBP, and maximum value of SBP surge (-0.468 mm Hg; P<0.001), defined as the difference between the hypoxia-peak SBP and the minimum nocturnal SBP independent of sleep stage. These values were not associated with the duration of each OSA episode. The contribution of rapid eye movement sleep and severe oxygen desaturation to OSA-related BP elevation measured with a noninvasive oscillometric method was determined in a clinical setting.

Evaluation of tolerance to ambulatory blood pressure monitoring: Analysis of dipping profile in a large cohort of hypertensive patients

Ambulatory blood pressure monitoring (ABPM) is a helpful tool to comprehensively identify and diagnose arterial hypertension. Moreover, it allows to better identify alterations in the circadian BP profile, as the nocturnal "nondipping" status, characterized by a lack of the physiological 10% night BP reduction and associated with a greater risk of target organ damage. However, ABPM has some limitations such as restricted availability, discomfort, particularly at night, cost implications, and reproducibility.Aim of the study was evaluate if the "nondipping" phenomenon may be related to low degree of tolerance to ABPM. Additionally, to determine whether self-reported events of sleep disorders and nighttime urinations may affect the "nondipping" status.From January 2013 to December 2015, we consecutively evaluated 1046 patients with arterial hypertension, performing ABPM, considering a tolerance index calculated on the basis of the patients' responses to a questionnaire.Thirty-eight out of 1046 patients showed complete lack of tolerance to the instrument during the day, whilst 126 during the night. There were no statistically significant differences in daytime and nighttime values of tolerance to the instrument between "dippers" and "nondippers," between "extreme-dippers" and the remaining patients or between "reverse-dippers" and the remaining patients. There were no statistically significant differences in the number of nocturnal awakenings between the groups. However, we found that the number of awakenings followed by urination was higher in "nondipping" patients and in "reverse-dipping" patients compared to the other groups.We found that the poor tolerance to the instrument does not seem to influence the BP "dipping" phenomenon among hypertensive individuals. Moreover, we think that in the evaluation of the ABPM data, factors, such as nocturnal urination and sleep disorders, need to be carefully taken into account, since may lead to a higher incidence of "nondipping" pattern.

Fine particulate matter results in hemodynamic changes in subjects with blunted nocturnal blood pressure dipping

Particulate matter with aerodynamic diameter of <2.5 μm (PM2.5) is associated with blood pressure and hemodynamic changes. Blunted nocturnal blood pressure dipping is a major risk factor for cardiovascular events; limited information is available on whether PM2.5 exposure-related hemodynamic changes vary with day-night blood pressure circadian rhythms. In this study, we enrolled 161 subjects and monitored the changes in ambulatory blood pressure and hemodynamics for 24h. The day-night blood pressure and cardiovascular metrics were calculated according to the sleep-wake cycles logged in the subject׳s diary. The effects of PM2.5 exposure on blood pressure and hemodynamic changes were analyzed using generalized linear mixed-effect model. After adjusting for potential confounders, a 10-μg/m(3) increase in PM2.5 was associated with 1.0 mmHg [95% confidence interval (CI): 0.2-1.8 mmHg] narrowing in the pulse pressure, 3.1% (95% CI: 1.4-4.8%) decrease in the maximum rate of left ventricular pressure rise, and 3.6% (95% CI: 1.6-5.7%) increase in systemic vascular resistance among 79 subjects with nocturnal blood pressure dip of <10%. In contrast, PM2.5 was not associated with any changes in cardiovascular metrics among 82 subjects with nocturnal blood pressure dip of ≥10%. Our findings demonstrate that short-term exposure to PM2.5 contributes to pulse pressure narrowing along with cardiac and vasomotor dysfunctions in subjects with nocturnal blood pressure dip of <10%.

Nocturia in arterial hypertension: a prevalent, underreported, and sometimes underestimated association

Nocturia is a risk factor for morbidity and mortality but is frequently overlooked and underreported by patients and unrecognized by physicians. Epidemiologic studies reported that nocturnal voiding is associated not only with aging and benign prostatic hyperplasia, but also with many other clinical conditions. The majority of epidemiologic studies reported a significant relationship between nocturia and hypertension. However, the cause-and-effect relationship between them has not been established. Some physiopathological changes in hypertension are conducive to result in nocturia. These include the effects of hypertension on glomerular filtration and tubular transport, resetting of the kidney pressure-natriuresis relationship, atrial stretch and release of atrial natriuretic peptide when congestive heart failure complicates hypertension, and peripheral edema. Another link between hypertension and nocturia is obstructive sleep apnea. Furthermore, some evidence supports the relationship between nondipping behavior of blood pressure and an increased prevalence of nocturia. The use of some classes of antihypertensive agents may result in nocturia. The present review aims to provide a comprehensive evaluation of the epidemiologic evidence and physiopathological links that correlate hypertension and nocturia. Emphasis is placed on the need to take a pro-active attitude to detect and treat this hazardous condition.

Short-term increase in particulate matter blunts nocturnal blood pressure dipping and daytime urinary sodium excretion

Short-term exposure to ambient particulate matter with aerodynamic diameters<10 µm were found to be positively associated with blood pressure. Yet, little information exists regarding the association between particles and circadian rhythm of blood pressure. Hence, we analyzed the association of exposure to particulate matter with aerodynamic diameters<10 µm on the day of examination and ≤7 days before with ambulatory blood pressure and with sodium excretion in 359 adults from the general population using multiple linear regression. After controlling for potential confounders, a 10-µg/m3 increase in particulate matter with aerodynamic diameters<10 µm levels was associated with nighttime systolic blood pressure (β=1.32 mm Hg 95% CI, 0.06-2.58 mm Hg at lag 0; P=0.04), nighttime diastolic blood pressure (0.72 mm Hg 95% CI, 0.03-1.42 mm Hg at lag 2; P=0.04), nocturnal systolic blood pressure dipping (-0.96 mm Hg 95% CI, -1.89 to -0.03 mm Hg at lag 0; P=0.044), and daytime urinary sodium excretion (-0.05 log-mmol/min 95% CI, -0.10 to -0.01 log-mmol/min at lag 0; P=0.027) but not with nighttime sodium excretion. The associations with blood pressure rapidly diminished with increasing lag days, and the associations with daytime sodium excretion were maximal with particulate matter with aerodynamic diameters<10 µm in exposures 2 to 5 days before. The associations of short-term increases in particulate matter with aerodynamic diameters<10 µm with higher nighttime blood pressure and blunted systolic blood pressure dipping were preceded by associations with reduced ability of the kidney to excrete sodium during daytime. The underlying mechanism linking air pollution to increased cardiovascular risk may include disturbed circadian rhythms of renal sodium handling and blood pressure.

The morning blood pressure surge and all-cause mortality in patients referred for ambulatory blood pressure monitoring

BACKGROUND

Morning blood pressure surge (MS) is accepted to increase cardiovascular risk, but it is not clear how it should be defined. Because dipping on 24-h ambulatory blood pressure monitoring (ABPM) associates with improved outcome we hypothesized that MS will not predict mortality independent of dipping.

METHODS

We investigated a cohort of 2,627 patients referred for ABPM with available values for at least 1-h after awakening, and related them to all-cause mortality.

RESULTS

During 22,353 person-years of follow-up, 246 patients died. We used Cox proportional hazards models to explore mortality associated with different definitions of the MS. Only the "1-h" MS (difference between average blood pressure (BP) 1-h before and after awakening) was related to mortality: after multiple adjustments including 24-h systolic BP, those whose "1-h" MS was above median (>12 mm Hg) had mortality hazard ratio (HR) of 0.61, 95% CI: 0.47-0.79, P < 0.001. In predetermined subgroup analyses, nondippers (n = 1,039), had a highly significant MS-related decrease in mortality: HR 0.49, 95% CI: 0.34-0.73, P < 0.001, unlike dippers (n = 1,588), HR = 0.90, 95% CI: 0.60-1.34.

CONCLUSION

Among nondipping subjects referred for ABPM, the MS is associated with decreased mortality.

Stress, menopausal status and nocturnal blood pressure dipping patterns among hypertensive women

BACKGROUND

A less than 10% decline in blood pressure during the night is known as a nondipping blood pressure (BP) pattern. Nondipping BP has been shown to be associated with target organ damage and poorer cardiovascular outcomes. Additionally, some evidence suggests that hyper-tensive nondipping women are at greater risk for target organ damage than hypertensive nondipping men.

OBJECTIVE

To determine whether stress, demographics, menopausal status or sleep quality are associated with nondipping BP among hyperten-sive women.

METHODS

A cross-sectional study design was used to describe the rela-tionship between stress and dipping status among a sample of hypertensive women and to describe the sample by age, ethnicity, marital status, meno-pausal status, current medications and sleep quality.

RESULTS

The study sample consisted of 47 women (mean [+/- SD] age 57+/-13.9 years) with essential or office hypertension who underwent 24 h ambulatory BP monitoring, and completed stress and sleep quality measurements. Thirty-one women (66%) were classified as dippers and 16 (34%) were classified as nondippers. Nondippers were older (P=0.04), postmenopausal (P=0.003) and had lower stress scores (P=0.02) than their dipper counterparts. Postmenopausal status sig-nificantly predicted nondipping (OR 16; 95% CI 1.9 to 136.4).

CONCLUSION

These findings were of interest given that some women had a nondipping BP pattern and significantly lower stress scores. It is pos-sible that there are fundamentally different physiological mechanisms that explain this nondipping phenomenon. In the future, the identification of specific hemodynamic mechanisms associated with nondipping could potentially influence the choice of antihypertensive treatment regimens for nondipper hypertensive patients.

Dynamic blood pressure changes and recovery under different work shifts in young women

BACKGROUND

Some studies have reported that shift work can affect blood pressure (BP), but few have studied recovery from BP changes occurring during different shifts.

METHODS

We recruited 16 young female nurses working rotating shifts and six working the regular day shift. All received repeated ambulatory BP monitoring (ABPM) during their workdays and following day off.

RESULTS

Our linear mixed-effect model showed that both systolic and diastolic BPs were significantly decreased during sleeping period and significantly increased while on working period, on a work day, but increased during sleeping period after a night shift or evening shift. BP measurements that changed after evening shift usually returned to baseline on consecutive off-duty day after day shift, but they did not completely return to baseline after a night shift (P < 0.05). We also found 69% of those working rotating shifts had at least changed once in dipper/nondipper status. The rates of change in dipper/nondipper status between work day and off-duty day were 33, 44, 50, and 38% for nurses worked in outpatient clinic, night shift, evening shift, and day shift, respectively.

CONCLUSION

Shift work is significantly associated with BP and possibly dipper/nondipper status in young female nurses. Except for those working night shifts, BP levels returned to baseline the off-duty day after day shift. We recommend that potential influence of shift work be considered when evaluating a person's BP.

Usefulness of nocturia as a mortality risk factor for coronary heart disease among persons born in 1920 or 1921

Cardiovascular events are clustered in the morning hours, after increases in blood pressure and heart rate that accompany awakening and arising. Similar hemodynamic changes occur during the night after nocturnal awakening and getting up. Such changes are common among older patients who have nocturia frequently and rise to urinate. We tested the hypothesis that nocturia may be associated with increased mortality in a population sample of 456 subjects born from 1920 to 1921, examined in 1990, and followed for total mortality until 2002. At baseline, they were questioned about nocturia (> or =2 times at night) as part of a detailed questionnaire and examination. Twelve-year survival was significantly lower (61% vs 72%, p = 0.0206) among subjects reporting nocturia (n = 160, 64% men) compared with those without nocturia (n = 296, 50% men). After accounting for numerous confounders, a proportional hazard model determined the mortality hazard ratio (HR) for nocturia alone to be 0.89 (95% confidence interval [CI] 0.55 to 1.43). The interaction between nocturia and previous coronary heart disease (CHD) was highly significant (p <0.0001), with an interaction variable HR of 2.16 (95% CI 1.01 to 4.61). Survival of patients who had CHD with nocturia (n = 54) versus those without nocturia (n = 65) was 44% versus 66% (p = 0.0201). Among patients with CHD, the mortality HR for nocturia was 2.11 (95% CI 1.16 to 4.00). In conclusion, nocturia is a significant independent predictor of mortality among 70-year-old patients with known CHD and thus warrants special attention.

How should patients treated with alpha-blockers be followed? Insights from an ambulatory blood pressure monitoring database

OBJECTIVE

Adrenergic alpha-antagonists have been suggested to confer lesser protection, compared to diuretics, when used as first agents for hypertension. While differences in clinic blood pressure may be partly responsible, this inferiority is unexpected in light of the metabolic advantages of alpha-blockade. The aim of this study was to evaluate the relationship between use of alpha-blockers and blood pressure dipping.

METHODS

A database of a 24-h ambulatory monitoring service was cross-sectionally evaluated for associations between antihypertensives and dipping. There were 681 treated subjects during a 3-year period (age 63 +/- 14, 57% female).

RESULTS

Overall, 78 of 681 treated hypertensive subjects used alpha-blockers (11%). Nine per cent of dippers and 16% of nondippers were treated with alpha-blockade, odds ratio 2.0. Whereas clinic, 24-h, and awake blood pressures were similar in alpha-blocker users and nonusers, sleep blood pressure was significantly higher in the former group. Furthermore, significantly fewer subjects given alpha-blockers had a controlled sleep blood pressure. Among alpha-blocker nonusers sleep blood pressure was the best controlled category, whereas in alpha-blocker users manual blood pressure had the highest rate of control. Generally, accounting for covariates of alpha-blockade (age, gender, diabetes, total number of medications) did not influence the above-mentioned trends. Finally, a limited negative dose-response relationship between alpha-blockade and dipping magnitude was also noticed.

CONCLUSIONS

We found a significant negative association between adrenergic alpha-blockade and the magnitude of sleep-related blood pressure decline. Awaiting results from interventional studies, this may suggest a need to perform ambulatory monitoring in patients given alpha-blocking agents (or at least supine and standing measurements), and may partially clarify the inferiority of doxazosin in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT).

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.

Blood pressure dipping is reproducible in clinical practice

OBJECTIVE

Blood pressure dipping pattern has clinical and prognostic consequences. However, reproducibility of night-time blood pressure fall during 24-h ambulatory blood pressure monitoring is considered limited. This limited reproducibility is possibly a result of inadequate day-night definitions. We retrospectively examined the reproducibility of blood pressure dipping in clinical practice, applying a method that accounts for sleep-awake states and does not rely on arbitrary day-night definitions. We also examined dipping repeatability in subjects with changing blood pressure.

METHODS

Of 962 consecutive ambulatory measurements performed in our unit during a 3-year period, 100 patients (age 60+/-15) had a prior session, and were the subjects of this study. Based on patients' report we defined 'awake blood pressure' as the average of pressure recordings while the subject was awake, including night-time arousals, and 'sleep blood pressure' as the average of pressure recordings while the subject was sleeping, including afternoon naps.

RESULTS

We found systolic blood pressure dipping not less reproducible than 24-h, awake- and sleep systolic blood pressure, as evaluated by both Pearson correlations (r=0.52 versus 0.5, 0.5, 0.49, respectively, P < or =0.0002 in all), and Bland-Altman repeatability. In a subgroup of 35 subjects (age 63+/-15) with at least 10 mmHg change in systolic blood pressure between the two sessions, systolic blood pressure dipping remained reproducible (r=0.45, P<0.007).

CONCLUSIONS

When interpreted in a way that accounts for sleep-awake pattern, sleep-induced systolic blood pressure dipping in clinical practice is a very reproducible feature of ambulatory blood pressure monitoring, in accordance with its vital prognostic implications.

Effect of the Angiotensin-Converting Enzyme Inhibitor Perindopril on 24-Hour Blood Pressure in Patients with Lacunar Infarction: Comparison between Dippers and Non-Dippers

Antihypertensive therapy based on the angiotensin-converting enzyme (ACE) inhibitor perindopril reduced the incidence of recurrent stroke in the Perindopril Protection against Recurrent Stroke Study (PROGRESS). The present study assessed the effect of perindopril on the 24-h blood pressure (BP) in hypertensive patients with lacunar infarction using ambulatory BP monitoring (ABPM). There was a 4-week observation period, a 4-week treatment period 1 (perindopril at 2 mg/day), and a 4-week treatment period 2 (perindopril at 4 mg/day). Twenty-seven hypertensive patients with lacunar infarction (10 dippers and 17 non-dippers) were enrolled. The average 24-h BP values were significantly decreased after both treatment periods. When the patients were divided into dippers and non-dippers, perindopril exhibited a different BP-lowering effect in the groups with these two circadian BP patterns. In dippers, daytime BP was significantly decreased, whereas nighttime BP was not, so an excessive fall of nighttime BP was not observed. In non-dippers, both daytime and nighttime BP were decreased, with a stronger BP-lowering effect at night. There was a significant inverse correlation between the magnitude of the change in nighttime BP and the night/day ratio. These results suggested that perindopril could induce a sustained decrease of the 24-h BP in patients with lacunar infarction. In particular, a more pronounced nighttime BP-lowering effect was observed in non-dippers. As the incidence of non-dippers is reported to be high among patients with cerebrovascular disease, better nighttime BP control by perindopril might have helped to improve the outcome of such patients in PROGRESS.

Time-series analysis of systolic blood pressure variation in thirty-three Uygur centenarians in China

The Uygur are reported to have an unusually long life expectancy. The purpose of this research was to perform a time-series analysis of systolic blood pressure (SBP) variations in the Uygur and clarify the role of blood pressure variation (BPV) in their longevity. A cross-sectional survey was carried out in Hotan. We investigated 133 clinically healthy elderly Uygur subjects and divided them into two groups: 1) 33 Uygur centenarians in Hotan (UCH; aged > or = 100 years); and 2) 100 elderly Uygur in Hotan (UEH; aged 65-70 years). Blood pressure (BP) was monitored and analyzed with ambulatory BP monitoring. The frequency domain measures were obtained with the maximum entropy method. The mean 24-h SBP was higher in UCH than in UEH. The ratio of non-dipper type BPV was larger in the UCH than in UEH. The highest power spectral density occurred over a 12-h rather than a 24-h period in both UCH and UEH. Ultradian BPVs were more frequent in UCH than in UEH. The least square-fitting curves demonstrated that the maximum values, minimum values, and mean 24-h SBP values were higher in UCH than in UEH. The higher BP and greater number of ultradian BPVs in UCH may have been due to the greater energy expenditure for maintaining daily activities in this population. Factors such as meals, daytime naps, nocturnal micturition, decreased baroreceptor sensitivity, and arterial sclerosis may also have contributed to the higher ultradian BPVs. In conclusion, BPV in the 12-h is more dominant than in the 24-h in both UCH and UEH. BPVs in the 3-h and 4-h are more frequent in UCH than those in UEH.

Ambulatory pulse pressure is a relatively sleep-independent variable

OBJECTIVES

Characterization of sleep-induced pulse and mean arterial pressure (MAP) dip.

DESIGN

Prospective study of consecutive referred patients.

SETTING

Hypertension unit of community university hospital.

PARTICIPANTS

A total of 500 consecutive subjects referred to our unit for ambulatory blood pressure (BP) monitoring. There were 200 men and 300 women, the majority of which were treated hypertensives. Mean age was 59.7 +/- 16.6 years.

MAIN OUTCOME MEASURES

Effect of sleep on MAP and pulse pressure (PP).

RESULTS

Twenty-four hour MAP was 98 +/- 10 mmHg. Awake and asleep MAPs were 101 +/- 11 and 87 +/- 11 mmHg, respectively. Twenty-four hour, awake and asleep pulse pressures were 60 +/- 13, 61 +/- 13 and 58 +/- 13 mmHg, respectively. MAP dip was 14%, 95% confidence interval (CI) 13.4-14.6, whereas PP dip was 5%, 95% CI 4.1-5.8. Thus, the MAP dip was almost three times the PP dip (P < 0.0001). This held true for normotensives, hypertensives (treated and untreated), men, women and diabetic subjects.

CONCLUSIONS

Although pulse pressure is derived from BP, it is more stable during a 24-h period, with a lesser effect of sleep compared with MAP. This more rigid nature of the PP could explain its better prognostic value, compared to that of MAP.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.

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.

Non-dipping in diabetic patients: insights from the siesta

Non-dipping, ie failure to lower blood pressure during sleep, has been found to be more prevalent in diabetic than in non-diabetic subjects. However, the reasons remain to be clarified. Diabetic patients may wake up more frequently during the night (for instance, due to nocturia). This may result in inclusion of awake blood pressure measurements in the night-time average and thus erroneously raise this average, causing misclassification of patients as non-dippers. However, non-dipping in diabetes may be due to blunted effect of sleep itself on blood pressure secondary to autonomic neuropathy. We undertook this study in order to further clarify this question. We studied 23 diabetic patients, and 23 matched controls who underwent 24-h ambulatory blood pressure monitoring, and reported taking an afternoon nap. Afternoon nap, by virtue of its short duration, is devoid of interruptions, and thus can be used as a model for tiled, non-interrupted sleep. We found that, both in diabetic patients and controls, blood pressure declined during the afternoon nap in a similar magnitude to the night-time decline. However, this decline was significantly blunted in the diabetic patients (13.9 +/- 2.2% decline in diastolic blood pressure during naptime in the diabetic patients, as compared with 24 +/- 2.3% decline in diastolic blood pressure during the siesta in the control group, P < 0.02). The blunted decline of blood pressure during the nap in diabetic patients demonstrates that non-dipping is due to the blunted effect of sleep itself. This can be another facet of autonomic dysfunction seen in diabetes mellitus.

Diurnal blood pressure patterns in long-term care settings

BACKGROUND

Some research suggests that individuals whose blood pressure does not decline at night may be at increased risk of end-organ damage. Few studies have examined ambulatory blood pressure among elders, particularly those living in institutions. This study therefore evaluates ambulatory blood pressure variation in two groups of institutionalized elderly, independent living and nursing home residents. It was suggested that the nursing home sample would have a higher rate of non-dipping than the independent-living residents.

DESIGN AND METHODS

Twenty-seven residents (aged 87 +/- 8 years) of a nursing home facility and 29 residents (aged 80 +/- 6 years) from two independent living facilities wore ambulatory monitors for approximately 24 h. Several definitions of dipping were examined.

RESULTS

Neither mean daytime nor mean night-time systolic blood pressure differed between the two groups. Daytime diastolic blood pressure was significantly higher in the independent living sample, as was night-time diastolic pressure in the nursing home residents. Neither asleep nor awake blood pressure varied significantly between groups. The decline in night-time blood pressure and sleep blood pressure was significantly greater among the independent living residents (P < 0.05). Ratios of night-time/daytime and asleep/awake blood pressure were significantly higher in the nursing home group. Non-dippers were significantly more frequent among the nursing home residents.

CONCLUSIONS

Nursing home residents were significantly more likely to be non-dippers. Both groups of resident were more frequently non-dippers than were individuals in community-dwelling samples. The high prevalence of non-dipping among institutionalized elderly people may be a result of age, health status or institutional activity patterns.