Nighttime Blood Pressure Dipping Research Articles

Stress, cortisol, and nighttime blood pressure dipping in nonhypertensive Black American women.

Black American women have among the highest hypertension (HTN) rates in the world. Research suggests that nighttime might be a critical period of vulnerability for the development of HTN in Blacks. In the present study, personal factors (age, body fat, income, family history), psychological factors (stress, emotions, and John Henryism), and physiological factors (salivary cortisol and blood pressure [BP]) were explored in 30 Black women, ages 26-51 years. Data were collected in participants' homes. BP was monitored while participants were awake and asleep. Cortisol samples were obtained within the first hour after awakening. The usual pattern for BP is a drop or dipping of 10-20% during sleep; however, the BP for about a third of the subjects did not dip adequately during sleep. Though not statistically significant, this nondipping was clinically relevant and was associated with positive family history of HTN, more stress, lower positive and higher negative affect scores, and higher early morning cortisol levels. These findings add to the HTN risk profile and support the need to further explore the relationship between nondipping nighttime BP and cardiovascular disease in Black women.

The effect of job strain on nighttime blood pressure dipping among men and women with high blood pressure

Blunted nighttime blood pressure dipping is an established cardiovascular risk factor. This study examined the effect of job strain on nighttime blood pressure dipping among men and women with high blood pressure. The sample consisted of 122 blue- and white collar workers (men=72, women=50). The Job Content Questionnaire was used to measure job psychological demands, job control, and social support. The ratio of job demands to job control was used to assess job strain. Nighttime blood pressure dipping was evaluated from 24-hour ambulatory blood pressure monitoring performed on three workdays. Men with high job strain had a 5.4 mm Hg higher sleep systolic blood pressure (P=0.03) and 3.5 mm Hg higher sleep pulse pressure (P=0.02) compared to men with low job strain. Men with high job strain had a smaller fall in systolic blood pressure and pulse pressure from awake to sleep state than those with low job strain (P<0.05). Hierarchical analyses showed that job strain was an independent determinant of systolic blood pressure dipping (P=0.03) among men after adjusting for ethnicity, body mass index, anxiety and depression symptoms, current smoking status, and alcohol consumption. Further exploratory analyses indicated that job control was the salient component of job strain associated with blood pressure dipping (P=0.03). High job strain is associated with a blunting of the normal diurnal variation in blood pressure and pulse pressure, which may contribute to the relationship between job strain and cardiovascular disease.

Nighttime Blood Pressure Dipping in Young Adults and Coronary Artery Calcium 10-15 Years Later: The Coronary Artery Risk Development in Young Adults Study

Nighttime Blood Pressure Dipping in Young Adults and Coronary Artery Calcium 10-15 Years Later: The Coronary Artery Risk Development in Young Adults Study

Nighttime Blood Pressure Dipping in Postmenopausal Women With Coronary Heart Disease

Nighttime Blood Pressure Dipping in Postmenopausal Women With Coronary Heart Disease

Acute Exercise Is Associated With Greater Nighttime Blood Pressure Dipping In Women Classified As Non-dippers

Acute exercise has been shown to improve the non-dipping (ND) blood pressure pattern in hypertensive individuals. Prehypertensive individuals have increased risk for developing hypertension and for having a ND pattern. PURPOSE: To assess whether acute exercise affects the non-dipping blood pressure of prehypertensive individuals. METHODS: We assessed 24-hour blood pressure patterns in low to moderately active normotensive (n=8) and prehypertensive (n=22) women. Ten of the prehypertensive had a ND pattern for mean arterial pressure (MAP). Participants wore an ambulatory blood pressure monitor on two days separated by one week. In the first session, participants wore the monitor on a non-exercise weekday, and walked on a treadmill for 30 minutes at a moderate intensity before the second 24-hour measurement. Participants kept activity diaries and sleep records for each measurement. Repeated measures ANOVA was used to assess group differences across conditions. RESULTS: The condition effect was not significant (p=.30) and the group by condition interaction approached significance (p=.08). The group effect was significant (p=.009). This difference was characterized by greater dipping in the normotensive and dipper prehypertensive participants compared to ND prehypertensive participants. Although the interaction effect was not significant, ND prehypertensive participants were the only group to experience greater MAP dipping after acute exercise. CONCLUSION: Our results indicate that the ND pattern for MAP can be improved with moderate intensity acute exercise in ND women at increased risk for developing hypertension. Supported by: College of William & Mary Summer Research Grant; Borgenicht Program for Aging Studies and Exercise Science

Clinical variables associated with non-dipping of nocturnal blood pressure in type 2 diabetes

Aim Non-dipping of nocturnal BP (blood pressure) is common in people with type 2 diabetes and is associated with increased risk of cardiovascular morbidity and mortality. This study aimed to identify the factors associated with nocturnal non-dipping of BP in people with type 2 diabetes. Methods Data were examined from 100 people with type 2 diabetes who had undergone ambulatory BP monitoring. Dippers were defined as those with a systolic night-time BP dip over 15%, and non-dippers as those with a systolic night-time BP dip of under 5%. Results There was no significant difference between the mean awake systolic BP in the dipping (142.9 mmHg) and the non-dipping (142.0 mmHg) groups (p=0.77). Non-dippers were significantly older (p&lt;0.0001) with a higher prevalence of albuminuria (p=0.003) and of macrovascular disease (p=0.008) when compared with the dipping group. After adjustment for age, albuminuria remained more prevalent within the non-dipping group (p=0.007). There was no significant difference in glycaemic control, type of diabetes treatment, smoking status, or gender between the groups. Conclusion Albuminuria is strongly associated with non-dipping of nocturnal BP in people with type 2 diabetes.

Nocturnal Blood Pressure Fall Changes in Correlation With Urinary Sodium Excretion

HomeHypertensionVol. 52, No. 2Nocturnal Blood Pressure Fall Changes in Correlation With Urinary Sodium Excretion Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBNocturnal Blood Pressure Fall Changes in Correlation With Urinary Sodium Excretion Katia Coelho Ortega, Giovanio Vieira da Silva and Décio MionJr Katia Coelho OrtegaKatia Coelho Ortega Hypertension Unit, Nephrology Division, University of São Paulo–School of Medicine, São Paulo, Brazil Search for more papers by this author , Giovanio Vieira da SilvaGiovanio Vieira da Silva Hypertension Unit, Nephrology Division, University of São Paulo–School of Medicine, São Paulo, Brazil Search for more papers by this author and Décio MionJrDécio MionJr Hypertension Unit, Nephrology Division, University of São Paulo–School of Medicine, São Paulo, Brazil Search for more papers by this author Originally published7 Jul 2008https://doi.org/10.1161/HYPERTENSIONAHA.108.115394Hypertension. 2008;52:e10Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: July 7, 2008: Previous Version 1 To the Editor:In the April 2008 issue of Hypertension, Bankir et al1 analyzed the data of 325 subjects divided into tertiles of the day:night ratio of urinary sodium excretion. Subjects in tertile 3 were qualified as “high daytime sodium excretors” because they excreted sodium at a rate that was 46% higher during daytime than during nighttime, whereas subjects in tertile 1 were “low daytime sodium excretors” and excreted 3 times less sodium during daytime than during nighttime. The nocturnal blood pressure (BP) dipping was significantly lower in tertile 1 than in other tertiles, especially for systolic BP. Thus, the authors suggested that the capacity to excrete sodium during daytime is the main determinant of nocturnal BP and dipping.However, the mechanisms associated with the reproducibility of the circadian BP pattern remain to be elucidated. It is well known that when ambulatory BP monitoring (ABPM) is repeated without interventions in the short2 or long term,3 a spontaneous change may occur in the nocturnal BP.Thus, we4 investigated whether individuals with a spontaneous change in the nocturnal BP fall have any differences in physiological mechanisms of BP control. Normotensive and hypertensive subjects underwent two 24-hour ABPM recordings separated by 30 days and also measurements in the same period of plasma renin activity, aldosterone, catecholamines, and 24-hour urinary sodium/potassium excretion.Twenty-three individuals (50%) maintained the same nocturnal systolic and diastolic BP fall profile, “dipper” (n=14) or “nondipper” (n=9), designated as the “maintained” group. In 23 individuals (50%), the nocturnal BP fall profile changed, from dipper to nondipper (n=16) or from nondipper to dipper (n=7), called the “changed group.” The maintained and changed groups were not different in relation to age, body mass index, gender, plasma renin activity, aldosterone, catecholamines, and 24-hour urinary potassium excretion.However, it was observed that, in the changed group, the subgroup that changed from dipper (ABPM 1) to nondipper (ABPM 2) had a significant increase in nocturnal BP on ABPM 2 (123±16 to 131±19 mm Hg; P<0.05) and lower urinary sodium excretion (151±65 versus 112±48 mEq/24 hours; P<0.05) and a negative correlation between the difference in nighttime ambulatory systolic BP (ABPM 1 − ABPM 2) and in 24-hour urinary sodium excretion (r=−0.63; P=0.01).A explanation for this finding could be that the subjects in this subgroup probably had an elevation in nocturnal systolic BP during the second 24-hour recording because of lower sodium excretion in the daytime, as showed by Bankir et al.1 For a better understanding of this subject, further studies should be done to investigate the sodium excretion during daytime and nighttime in two 24-hour ABPM recordings.Source of FundingThis work was supported by a grant from FAPESP (03/08257-9).DisclosuresNone.1 Bankir L, Bochud M, Maillard M, Bovet P, Gabriel A, Burnier M. Nighttime blood pressure and nocturnal dipping are associated with daytime urinary sodium excretion in African subjects. Hypertension. 2008; 51: 891–898.LinkGoogle Scholar2 Mochizuki Y, Okutani M, Donfeng Y, Iwasaki H, Takusagawa M, Kohno I, Umetani K, Ishii H, Ijiri H, Komori S, Tamura K. Limited reproducibility of circadian variation in blood pressure dippers and nondippers. Am J Hypertens. 1998; 11: 403–409.CrossrefMedlineGoogle Scholar3 Omboni S, Parati G, Palatini P, Vanasia A, Muiesan ML, Cuspidi C, Mancia G. Reproducibility and clinical value of nocturnal hypotension: prospective evidence from the SAMPLE study. J Hypertens. 1998; 16: 733–738.CrossrefMedlineGoogle Scholar4 Ortega KC, Mion D Jr. Sodium excretion and nocturnal blood pressure fall. World Congress of Nephrology 2007; April 21–25, 2007; Rio de Janeiro, Brazil. Book of Abstracts WCN T-PO-. 2007; 1171: 387.Google Scholar Previous Back to top Next FiguresReferencesRelatedDetails August 2008Vol 52, Issue 2 Advertisement Article InformationMetrics https://doi.org/10.1161/HYPERTENSIONAHA.108.115394PMID: 18606898 Originally publishedJuly 7, 2008 PDF download Advertisement SubjectsDiagnostic TestingHypertension

Nighttime Blood Pressure and Nocturnal Dipping Are Associated With Daytime Urinary Sodium Excretion in African Subjects

Blood pressure (BP) follows a circadian rhythm, with 10% to 15% lower values during nighttime than during daytime. The absence of a nocturnal BP decrease (dipping) is associated with target organ damage, but the determinants of dipping are poorly understood. We assessed whether the nighttime BP and the dipping are associated with the circadian pattern of sodium excretion. Ambulatory BP and daytime and nighttime urinary electrolyte excretion were measured simultaneously in 325 individuals of African descent from 73 families. When divided into sex-specific tertiles of day:night ratios of urinary sodium excretion rate, subjects in tertile 1 (with the lowest ratio) were 6.5 years older and had a 9.8-mm Hg higher nighttime systolic BP (SBP) and a 23% lower SBP dipping (expressed in percentage of day value) compared with subjects in tertile 3 (P for trend <0.01). After adjustment for age, the SBP difference across tertiles decreased to 5.4 mm Hg (P=0.002), and the SBP dipping difference decreased to 17% (P=0.05). A similar trend across tertiles was found with diastolic BP. In multivariate analyses, daytime urinary sodium and potassium concentrations were independently associated with nighttime SBP and SBP dipping (P<0.05 for each). These data, based on a large number of subjects, suggest that the capacity to excrete sodium during daytime is a significant determinant of nocturnal BP and dipping. This observation may help us to understand the pathophysiology and clinical consequences of nighttime BP and to develop therapeutic strategies to normalize the dipping profile in hypertensive patients.

Early Socioeconomic Status is Associated With Adult Nighttime Blood Pressure Dipping

To examine the prognostic significance of early socioeconomic status (SES) on 24-hour blood pressure (BP) during early adulthood. Low SES has been related to poor health outcomes, in particular, cardiovascular morbidity and mortality. Recent cross-sectional research has also linked low levels of SES with several cardiovascular risk factors including poor nighttime BP dipping. A total of 174 undergraduate university students whose childhood SES was assessed by highest level of education completed by their parents underwent 24-hour ambulatory BP monitoring. Initial correlation analyses revealed positive associations between childhood SES and BP dipping, indicating that lower levels of childhood SES were associated with less systolic BP (SBP) (r = .29, p < .01) and diastolic BP (DBP) dipping (r = .38, p < .01). A stepwise multiple regression analyses indicated that childhood SES explained 6.9% of the variance in SBP dipping and 11.5% of the variance in DBP dipping above and beyond other lifestyle-related factors including daytime BP, body mass index, alcohol use, smoking, and current SES. These findings suggest that irrespective of adult achievement, childhood SES may have lasting health implications.

Ethnic Differences in Sleep Quality Accompany Ethnic Differences in Night-time Blood Pressure Dipping

African Americans exhibit a smaller nocturnal decrease in blood pressure (BP) than whites, and there are also reports of poorer sleep quality among African Americans. We examined the contribution of sleep quality to ethnic differences in BP dipping in African American and white male and female college students. We hypothesized that African Americans would exhibit blunted nocturnal BP dipping compared to whites, which would be partly accounted for by poorer sleep quality among African Americans. Forty-three African American and 46 white college students aged 18 to 25 years completed an ambulatory BP protocol that included wrist actigraphy, which was used in conjunction with participant self-reports of sleep times for analyses of sleep quality. Although daytime and night-time BP did not differ according to ethnicity, African Americans had a smaller dip in systolic BP (P < .01), and African American women had a smaller dip in diastolic BP than whites (P < .01). Whites were more likely to be classified as a dipper (71%) than African Americans (41%) (P < .01). African Americans, compared to whites, spent less time in bed, were asleep for a shorter period of time, took longer to fall asleep, exhibited poorer sleep efficiency, and were awakened a higher percentage of the time by the inflation of the BP cuff (F > or = 4.85, P < .05). However, sleep quality did not appear to contribute to ethnic differences in diastolic BP dipping. Sleep quality accompanied ethnic differences in systolic and diastolic BP dipping, but did not account for these differences.

Hypertension and Exposure to Noise near Airports (HYENA): study design and noise exposure assessment.

An increasing number of people live near airports with considerable noise and air pollution. The Hypertension and Exposure to Noise near Airports (HYENA) project aims to assess the impact of airport-related noise exposure on blood pressure (BP) and cardiovascular disease using a cross-sectional study design. We selected 6,000 persons (45–70 years of age) who had lived at least 5 years near one of six major European airports. We used modeled aircraft noise contours, aiming to maximize exposure contrast. Automated BP instruments are used to reduce observer error. We designed a standardized questionnaire to collect data on annoyance, noise disturbance, and major confounders. Cortisol in saliva was collected in a subsample of the study population (n = 500) stratified by noise exposure level. To investigate short-term noise effects on BP and possible effects on nighttime BP dipping, we measured 24-hr BP and assessed continuous night noise in another sub-sample (n = 200). To ensure comparability between countries, we used common noise models to assess individual noise exposure, with a resolution of 1 dB(A). Modifiers of individual exposure, such as the orientation of living and bedroom toward roads, window-opening habits, and sound insulation, were assessed by the questionnaire. For four airports, we estimated exposure to air pollution to explore modifying effects of air pollution on cardiovascular disease. The project assesses exposure to traffic-related air pollutants, primarily using data from another project funded by the European Union (APMoSPHERE, Air Pollution Modelling for Support to Policy on Health and Environmental Risks in Europe).

Circadian Blood Pressure Patterns and Life Stress

Background: Scarce data are available on the influence of psychological aspects on 24-hour ambulatory blood pressure patterns either in normotensive or hypertensive subjects. This study was designed to evaluate the relationship between psychological profile and changes in daytime/nighttime blood pressure rhythm. Methods:Nocturnal dipping was defined as the night/day ratio of ambulatory mean systolic and/or diastolic blood pressure ≤0.87. Three-hundred and two outpatients (M/F = 174/128; mean age = 49.8 years, SD = 13.6; range, 16–80 years) underwent 24-hour ambulatory blood pressure monitoring. They were administered a self-rating scale, the Psychosocial Index, as an indicator of stress, psychological distress, sleep disturbances, well-being, abnormal illness behavior and quality of life. There were 242 patients taking antihypertensive medication (146 adequately controlled and 96 not controlled) and 60 who were drug free (33 never-treated hypertensive and 27 normotensive subjects). Patients were divided according to the presence (n = 125) or absence (n = 177) of night blood pressure dipping. The two groups were compared using analysis of covariance, with age as a covariate. Results: Dippers had lower (p < 0.001) nocturnal systolic and diastolic blood pressure than nondippers, and higher (p < 0.05) daytime diastolic blood pressure. Patients with nocturnal blood pressure decline had a markedly higher (p < 0.001) level of stress than nondippers. When the sample was divided according to the presence or absence of hypertension, only subjects with normalblood pressure showed nocturnal dipping associated with increased stressful life circumstances. Conclusions: Our findings indicate that dippers experience stressful life circumstances, both in terms of life events and chronic stress. Thissuggests that stress-reducing techniques may be particularly helpful in the setting of hypertension characterized by nighttime blood pressure dipping.

Nighttime blood pressure dipping: the role of the sympathetic nervous system

There is a marked diurnal variation in blood pressure (BP), with BP dipping to its lowest levels during nighttime sleep. A day–night dip in systolic BP (SBP) of <10% has been used to characterize individuals as nondippers, and is associated with an increased risk for cardiovascular disease. The present study examined the contribution of the sympathetic nervous system (SNS) to BP dipping in a biracial sample of 172 men and women aged 25 to 45 years. Assessments included 24-h ambulatory BP monitoring and both waking and sleeping urinary catecholamines. In addition, cardiovascular α- and β-adrenergic receptor (AR) responsiveness was determined by the doses of isoproterenol and phenylephrine required to attain an increase in heart rate of 25 points (CD 25) and BP (PD 25), respectively. Compared with dippers ( n = 116), nondippers ( n = 56) were more likely to be African American and to have a family history of hypertension as well as a higher body mass index (BMI). The nighttime fall in both norepinephrine (NE) and epinephrine (EPI) excretion rates was reduced in nondippers compared with dippers (NE dip 9.3 v 13.1 μg/mg; EPI dip 2.7 v 4.0 μg/mg; both P < .05). Nondippers also were characterized by heightened α 1-AR responsiveness compared with dippers (PD 25 = 252 v 321 μg, P < .05). These data suggest that the SNS may contribute to individual differences in nighttime BP dipping, and appears to account in part for blunted BP dipping in African Americans.

Blunted nighttime blood pressure dipping in postmenopausal women

Blunting of the normal drop in blood pressure (BP) from day to night is emerging as a strong prognostic indicator of cardiovascular morbidity and mortality. This study evaluated the effects of natural menopause on BP dipping in African American and white women. A total of 112 women (62 premenopausal and 50 postmenopausal) took part in the study. Pre- and postmenopausal groups were comparable in terms of clinic BP, body mass index, and ethnic composition. Ambulatory BP was recorded over 24 h during a typical workday, with measurements programmed to be taken every 15 min during waking hours and every 30-minutes during sleeping hours. Nocturnal BP dipping was defined as the difference between waking and sleep BP. Waking BP did not differ by menopausal status. However, nocturnal systolic BP (SBP) and diastolic BP (DBP) dipping were attenuated in postmenopausal women, with both SBP ( P < .05) and DBP ( P < .05) higher during nighttime sleep in postmenopausal than in premenopausal women. Ethnicity was also related to BP dipping, with African American women tending to show blunted SBP dipping ( P = .055) compared with white women; BP dipping was most blunted in postmenopausal African American women. These observations suggest that blunted nighttime BP dipping may contribute to increased cardiovascular disease risk in postmenopausal women.

Potassium intake is related to nocturnal blood pressure dipping

Sodium restriction and high levels of dietary potassium may contribute to a greater nocturnal decline in blood pressure. To evaluate the association of nutrient intake with the nighttime blood pressure dip, we measured 24-hour sodium and potassium excretion and performed ambulatory blood pressure monitoring in a sample of 165 young men and women with normal or mildly elevated blood pressure. Participants included 85 African-Americans and 80 whites with an average age of 33±6 years. Daytime systolic blood pressure averaged 125±13 mmHg, with a mean nighttime dip of 16±7 mmHg. The 24-hour sodium excretion averaged 137±61 mEq/24 hr, and potassium excretion averaged 52±25 mEq/24 hr. African-Americans and whites had similar levels of sodium excretion (132±64 vs 144±58 mEq/24 hr, p=NS), but potassium excretion was significantly lower in African-Americans (38±24 vs 59±28 mEq/24 hr, p<0.001). The nocturnal dip in systolic blood pressure was correlated with potassium excretion (r=0.25, p<0.01), and this association remained significant after adjusting for race (p<0.05) and for daytime blood pressure (p<0.01). Subjects with low potassium excretion (≤50mEq/24 hr) and those with high potassium excretion (>50mEq/24 hr) were similar in age (34±6 vs 33±6 years, p=NS) and daytime systolic blood pressure (124±13 vs 127±12 mmHg, P=NS), but participants with low potassium excretion were more often African-American (72% vs 22%, p<0.01) and had a smaller nighttime systolic blood pressure dip (15±7 vs 18±7 mmHg, p<0.01). In contrast, low sodium intake was not associated with a greater nocturnal systolic blood pressure decline. These results suggest that potassium consumption may be an important determinant of the nocturnal fall in blood pressure, and that dietary factors may contribute to ethnic differences in diurnal blood pressure variation.

Psychosocial mediators of racial differences in nighttime blood pressure dipping among normotensive adults.

Shallow declines in nocturnal compared with diurnal blood pressure (BP dipping) have been associated with cardiovascular disease. In U.S. samples, Blacks demonstrate less BP dipping compared with Whites. In a sample of 60 Black and 60 White normotensive adults we examined stress, social integration (including parental status), social support, and hostility as potential mediators of the association between race and BP dipping. The effect of race on diastolic BP dipping was partially mediated by parental status. The effect of race on heart rate dipping was partially mediated by stressful life events. No psychosocial factors mediated the relation between race and systolic BP dipping. Although psychosocial factors appear to account for some of the observed racial differences in nocturnal blood pressure decline, our data suggest that these differences cannot be attributed entirely to covarying psychosocial effects.

How Reliable Is Nighttime Blood Pressure Dipping?

This report examines the reliability of nighttime blood pressure dipping. Twenty-one individuals were studied twice with ambulatory blood pressure monitoring. On one occasion they were studied as outpatients, and on the other as inpatients on a clinical research ward. Blood pressure monitoring revealed the expected dip in blood pressure at nighttime. However, there was little test–retest reliability across the two settings. The test–retest correlations for the dip in blood pressure across the two settings were nonsignificant for systolic, diastolic, and mean arterial blood pressure. Caution is advised before diagnosing dipping or nondipping on the basis of one 24-h ambulatory blood pressure recording.

Metoprolol minimizes nighttime blood pressure dip in hypertensive black males: J.A. Johnson, W.S. Akers, S.T. Miller, W.B. Applegate. Department Clinical Pharmacy, University of Tennessee, Memphis, TN. Am J Hypertens 1995;8:254–9

Metoprolol minimizes nighttime blood pressure dip in hypertensive black males: J.A. Johnson, W.S. Akers, S.T. Miller, W.B. Applegate. Department Clinical Pharmacy, University of Tennessee, Memphis, TN. Am J Hypertens 1995;8:254–9

Metoprolol minimizes nighttime blood pressure dip in hypertensive black males

Twelve hypertensive black males completed the study, which was conducted to evaluate the effect of metoprolol on 24-h ambulatory blood pressure (ABP). Study participants took 50 mg to 100 mg metoprolol twice daily for a minimum of 3 weeks. Metoprolol had no significant effect on blood pressure (147/90 +/- 11/8 mm Hg v 151/88 +/- 16/8 mm Hg, baseline v treated, respectively) in spite of causing significant reductions in heart rate (87 +/- 9 beats/min v 69 +/- 7 beats/min, P < .001). Only one subject had a > or = 10 mm Hg decrease in 24-h diastolic blood pressure. The nighttime fall in blood pressure was minimized by metoprolol and clinically significant increases in daytime or nighttime blood pressure were noted in 58% of patients. Metoprolol therapy failed to lower blood pressure and eliminated the normal nighttime decline in blood pressure. Since the nighttime decline in blood pressure is thought to protect against target organ damage, it may be important to identify antihypertensive agents which preserve or enhance the nighttime blood pressure dip.