The influence of physical activity on the variability of ambulatory blood pressure

Ambulatory Blood Pressure Parameters Among Men With Hypogonadism Treated With Testosterone Transdermal Therapy

OBJECTIVE

Studies are needed to examine the effects of testosterone replacement therapy on ambulatory blood pressure (BP) parameters. This study assessed a testosterone transdermal system (TTS) using 24-hour ambulatory BP monitoring.

METHODS

In a single-arm, noninferiority trial conducted at 41 US sites, 168 men (mean age: 56.2 years) with hypogonadism not receiving testosterone replacement therapy in the past 6 months were enrolled and received ≥1 study drug dose. Nightly TTS treatment was administered for 16 weeks (starting dose: 4 mg/d; min, max dose: 2, 6 mg/d) to achieve testosterone concentration of 400-930 ng/dL. The primary endpoint was mean change from baseline to week 16 in 24-hour systolic BP (SBP). Noninferiority was determined based on the upper bound of the 2-sided 95% CI <3.0 mmHg.

RESULTS

Sixty-two men had ≥85% study drug compliance and a valid week 16 ambulatory BP monitoring session. Mean change from baseline to week 16 in 24-hour average SBP was 3.5 mmHg (95% CI, 1.2-5.8 mmHg; n = 62). Since the upper limit of the CI was >3 mmHg, an effect of TTS could not be ruled out. Mean changes were larger at daytime vs nighttime and in subgroups of men with vs without hypertension. Cardiovascular adverse events were rare (<2%) and nonserious; no major cardiovascular adverse events were reported.

CONCLUSION

A meaningful effect of 16-week TTS treatment on 24-hour average SBP among men with hypogonadism could not be ruled out based on the study's noninferiority criterion. The magnitude of mean changes observed may not be clinically meaningful regarding cardiovascular events.

Impact of sleep quality and physical activity on blood pressure variability

Increased blood pressure variability (BPV) is linked to cardiovascular disease and mortality, yet few modifiable BPV risk factors are known. We aimed to assess the relationship between sleep quality and activity level on longitudinal BPV in a cohort of community-dwelling adults (age ≥18) from 17 countries. Using Withings home measurement devices, we examined sleep quality and physical activity over one year, operationalized as mean daily step count and number of sleep interruptions, both transformed into tertiles. The primary study outcome was high BPV, defined as the top tertile of systolic blood pressure standard deviation. Our cohort comprised 29,375 individuals (mean age = 58.6 years) with 127.8±90.1 mean days of measurements. After adjusting for age, gender, country, body mass index, measurement days, mean blood pressure, and total time in bed, the odds ratio of having high BPV for those in the top tertile of sleep interruptions (poor sleep) was 1.37 (95% CI, 1.28-1.47) and 1.44 (95% CI, 1.35-1.54) for those in the lowest tertile of step count (physically inactive). Combining these exposures revealed a significant excess relative risk of 0.20 (95% CI, 0.04-0.35, p = 0.012), confirming their super-additive effect. Comparing individuals with the worst exposure status (lowest step count and highest sleep interruptions, n = 2,690) to those with the most optimal status (highest step count and lowest sleep interruptions, n = 3,531) yielded an odds ratio of 2.01 (95% CI, 1.80-2.25) for high BPV. Our findings demonstrate that poor sleep quality and physical inactivity are associated with increased BPV both independently and super-additively.

Influence of Recent Standing, Moving, or Sitting on Daytime Ambulatory Blood Pressure

Background There are no recommendations for being seated versus nonseated during ambulatory blood pressure (BP) monitoring (ABPM). The authors examined how recent standing or moving versus sitting affect average daytime BP on ABPM. Methods and Results This analysis used baseline assessments from a clinical trial in desk workers with office systolic BP (SBP) 120 to 159 mm Hg or diastolic BP (DBP) 80 to 99 mm Hg. ABPM was measured every 30 minutes with a SunTech Medical Oscar 2 monitor. Concurrent posture (standing or seated) and moving (steps) were measured via a thigh-worn accelerometer. Linear regression determined within-person BP variability explained (R2) by standing and steps before ABPM readings. Mean daytime BP and the prevalence of mean daytime BP >135/85 mm Hg from readings after sitting (seated) or after recent standing or moving (nonseated) were compared with all readings. Participants (n=266, 59% women; age, 45.2±11.6 years) provided 32.5±3.9 daytime BP readings. Time standing and steps before readings explained variability up to 17% for daytime SBP and 14% for daytime DBP. Using the 5-minute prior interval, seated SBP/DBP was lower (130.8/79.7 mm Hg, P<0.001) and nonseated SBP/DBP was higher (137.8/84.3 mm Hg, P<0.001) than mean daytime SBP/DBP from all readings (133.9/81.6 mm Hg). The prevalence of mean daytime SBP/DBP ≥135/85 mm Hg also differed: 38.7% from seated readings, 70.3% from nonseated readings, and 52.6% from all readings (P<0.05). Conclusions Daytime BP was systematically higher after standing and moving compared with being seated. Individual variation in activity patterns could influence the diagnosis of high BP using daytime BP readings on ABPM.

Masked Hypertension in Healthy Children and Adolescents: Who Should Be Screened?

PURPOSE OF REVIEW

The goal is to review masked hypertension (MH) as a relatively new phenomenon when patients have normal office BP but elevated out-of-office BP. Firstly, it was described in children in 2004. It has received increased attention in the past decade.

RECENT FINDINGS

The prevalence of MH in different pediatric populations differs widely between 0 and 60% based on the population studied, definition of MH, or method of out-of-office BP measurement. The highest prevalence of MH has been demonstrated in children with chronic kidney disease (CKD), obesity, diabetes, and after heart transplantation. In healthy children but with risk factors for hypertension such as prematurity, overweight/obesity, diabetes, chronic kidney disease, or positive family history of hypertension, the prevalence of MH is 9%. In healthy children without risk factors for hypertension, the prevalence of MH is very low ranging 0-3%. In healthy children, only patients with the following clinical conditions should be screened for MH: high-normal/elevated office BP, positive family history of hypertension, and those referred for suspected hypertension who have normal office BP in the secondary/tertiary center.

Acute ambulatory blood pressure response to short-term black carbon exposure: The MobiliSense sensor-based study

Documented relationships between black carbon (BC) exposure and blood pressure (BP) have been inconsistent. Very few studies measured both BC exposure and ambulatory BP across the multiple daily environments visited in the general population, and none adjusted for personal noise exposure, a major confounder. Our study addresses these gaps by considering 245 adults living in the Grand Paris region. Personal exposure to BC was monitored for 2 days using AE51 microaethalometers. Ambulatory BP was measured every 30 min after waking up using Arteriograph 24 monitors (n = 6772). Mixed effect models with a random intercept at the individual level and time-autocorrelation structure adjusted for personal noise exposure were used to evaluate the associations between BC exposure (averaged from 5 min to 1 h before each BP measurement) and BP. To increase the robustness of findings, we eliminated confounding by unmeasured time-invariant personal variables, by modelling the associations with fixed-effect models. All models were adjusted for potential confounders and short-term time trends. Results from mixed models show that a 1-μg/m³ increase in 5-minute averaged BC exposure was associated with an increase of 0.57 mmHg in ambulatory systolic blood pressure (SBP) (95 % CI: 0.30, 0.83) and with an increase of 0.36 mmHg in diastolic blood pressure (DBP) (95 % CI: 0.14, 0.58). The slope of the exposure-response relationship gradually decreased for both SBP and DBP with the increase in the averaging period of BC exposure from 5 min to 1 h preceding each BP measurement. Findings from the fixed-effect models were consistent with these results. There was no effect modification by noise in the associations, across all exposure windows. We found evidence of a relationship between BC exposure and acute increase in ambulatory SBP and DBP after adjustment for personal noise exposure, with potential implications for the development of adverse cardiovascular outcomes.

Association of ambulatory blood pressure with aortic valve and coronary artery calcification

OBJECTIVE

We aimed to investigate the effect of ambulatory blood pressure (BP) on aortic valve calcification (AVC) and coronary artery calcification (CAC), which are subclinical atherosclerotic diseases.

METHODS

In this population-based, cross-sectional study, we assessed office BP, mean ambulatory BP (24-h, awake, and asleep), and variability of ambulatory BP, as determined by the coefficient of variation (awake and asleep). AVC and CAC were quantified using an Agatston score (>0) based on computed tomography scanning. We calculated relative risks (RRs) and 95% confidence intervals (CIs) with a 1-standard deviation increment in each BP index for the presence of AVC and CAC using a multivariate-adjusted Poisson regression with robust error variance.

RESULTS

Of 483 participants (mean age: 66.8 years), 154 (31.9%) and 310 (64.2%) had AVC and CAC, respectively. The presence of AVC was associated with office systolic BP (SBP; RR, 1.15; 95% CI, 1.03-1.28), awake diastolic BP (DBP) variability (RR, 1.12; 95% CI, 1.01-1.25), and asleep SBP variability (RR, 1.14; 95% CI, 1.03-1.27). The presence of CAC was associated with office SBP (RR, 1.08; 95% CI, 1.01-1.15), mean 24-h SBP (RR, 1.10; 95% CI, 1.04-1.16), mean awake SBP (RR, 1.11; 95% CI, 1.04-1.17), mean asleep SBP (RR, 1.07; 95% CI, 1.01-1.13), and asleep SBP variability (RR, 1.07; 95% CI, 1.01-1.13).

CONCLUSION

These findings highlight the association of ambulatory BP indices with both AVC and CAC, but with different effects on their presences.

Examination stress in academic students: a multimodal, real-time, real-life investigation of reported stress, social contact, blood pressure, and cortisol

ObjectiveAcademic examinations are a frequent and significant source of student stress, but multimodal, psychophysiological studies are still missing. Participants & methods: Psychological and physiological variables were assessed on 154 undergraduate students in daily life using e-diaries resp. blood pressure devices at the beginning of the semester, and again before an examination. Results: Multilevel analysis revealed lower calmness, more negative valence, higher task-related stress, higher demands, lower perceived control, lower frequency of social contact, and a higher desire to be alone during the examination period (all p values < .0001), as well as lower ambulatory systolic blood pressure (p = .004), heightened cortisol at awakening (p = .021), and a smaller increase in cortisol (p = .012). Conclusions: Our study revealed empirical evidence that examination periods are not only associated with indicators of dysphoria, stress, and social withdrawal but also by altered physiological processes, which might reflect anticipatory stress and withdrawal effects.

Effect of Reducing Sedentary Behavior on Blood Pressure (RESET BP): Rationale, design, and methods

Sedentary behavior (SB) has recently been recognized as a strong risk factor for cardiovascular disease, with new guidelines encouraging adults to 'sit less, move more.' Yet, there are few randomized trials demonstrating that reducing SB improves cardiovascular health. The Effect of Reducing Sedentary Behavior on Blood Pressure (RESET BP) randomized clinical trial addresses this gap by testing the effect of a 3-month SB reduction intervention on resting systolic BP. Secondary outcomes include other BP measures, pulse wave velocity, plasma renin activity and aldosterone, and objectively-measured SB (via thigh-mounted activPAL) and physical activity (via waist-worn GT3X accelerometer). RESET BP has a targeted recruitment of 300 adults with desk jobs, along with elevated, non-medicated BP (systolic BP 120-159 mmHg or diastolic BP 80-99 mmHg) and physical inactivity (self-reported aerobic physical activity below recommended levels). The multi-component intervention promotes 2-4 fewer hours of SB per day by replacing sitting with standing and light-intensity movement breaks. Participants assigned to the intervention condition receive a sit-stand desk attachment, a wrist-worn activity prompter, behavioral counseling every two weeks (alternating in-person and phone), and twice-weekly automated text messages. Herein, we review the study rationale, describe and evaluate recruitment strategies based on enrollment to date, and detail the intervention and assessment protocols. We also document our mid-trial adaptations to participant recruitment, intervention deployment, and outcome assessments due to the intervening COVID-19 pandemic. Our research methods, experiences to date, and COVID-specific accommodations could inform other research studying BP and hypertension or targeting working populations, including those seeking remote methods.

Depiction of Physiological Homeostasis by Self-Coupled System and Its Significance

The negative feedback system (NFS) was regarded as the basic unit of regulation of physiological homeostasis for more than 70 years. However, NFS-based depiction possesses some limitations. The self-coupled system (SCS), a non-stop system in which the output of the current moment becomes the input of the next moment, can also be utilized to depict homeostasis. In SCS-based depiction, all of the related regulatory mechanisms of a homeostasis are regarded as an entity. Then, homeostatic dynamics can be expressed by simple mathematical language. A new disease group was revealed and some useful inferences were obtained through mathematical deduction. They were supported by published studies. SCS-based depiction of homeostasis should be a requisite supplement to medical knowledge systems based on NFS.

Labile and Paroxysmal Hypertension: Common Clinical Dilemmas in Need of Treatment Studies

Although "labile hypertension" is regularly encountered by clinicians, there is a paucity of information available to guide therapeutic decisions. This review discusses its clinical relevance, the limitations of current knowledge, and possible directions for future research and clinical management. Results of studies that assessed measures of blood pressure variability or reactivity are reviewed. The limited information about effects of antihypertensive drugs on blood pressure variability is discussed. Two different clinical presentations are differentiated: labile hypertension and paroxysmal hypertension. Labile hypertension remains a clinical impression without defined criteria or treatment guidance. Paroxysmal hypertension, also called pseudopheochromocytoma, presents as dramatic episodes of abrupt and severe blood pressure elevation. The disorder can be disabling. Although it regularly raises suspicion of a pheochromocytoma, such a tumor is found in <2 % of patients. The cause, which involves both emotional factors and the sympathetic nervous system, and treatment approaches, are presented.

Repetitive thought impairs sleep quality: an experience sampling study

Although previous research has suggested that presleep negative cognitive activities are associated with poor sleep quality, there is little evidence regarding the association between negative thoughts and sleep in real-life settings. The present study used experience sampling and long-term sleep monitoring with actigraphy to investigate the relationships among negative repetitive thought, mood, and sleep problems. During a 1-week sampling period, 43 undergraduate students recorded their thought content and mood eight times a day at semirandom intervals. In addition to these subjective reports, participants wore actigraphs on their wrists in order to measure sleep parameters. Analyses using multilevel modeling showed that repetitive thought in the evening was significantly associated with longer sleep-onset latency, decreased sleep efficiency, and reduced total sleep time. Furthermore, impaired sleep quality was significantly associated with reduced positive affect the next morning, and decreased positive affect was indirectly associated with increased repetitive thought in the evening. These findings suggest the existence of a self-reinforcing cycle involving repetitive thought, mood, and impaired sleep quality, highlighting the importance of cognitive and emotional factors in enhancement and maintenance of good-quality sleep.

A longitudinal study of blood pressure variability in African-American and European American youth

OBJECTIVES

High blood pressure variability is increasingly used as a predictor of target-organ damage and cardiovascular events. However, little is known about blood pressure variability changes with age and its possible sociodemographic, anthropometric, and genetic moderators.

METHODS

Twenty-four-hour ambulatory blood pressure was measured up to 12 times over a 15-year period in 344 European Americans and 297 African-Americans with an average age of 14 years at the initial visit. Blood pressure variability was indexed by the weighted 24-h standard deviation of ambulatory blood pressure recordings.

RESULTS

Both systolic and diastolic blood pressure variability increased with age and ambulatory blood pressure mean values. Men had higher levels of blood pressure variability (P < 0.001) and showed steeper linear increase rates with age than women. African-Americans showed higher values of blood pressure variability (P < 0.05) than European Americans. Body mass index and waist circumference were also associated with higher blood pressure variability levels (P < 0.001). Individuals with higher father's education level showed lower blood pressure variability. In the full model which included all the above factors, ethnic difference in systolic blood pressure variability was no longer significant.

CONCLUSION

The results of the present study suggest that men and African-Americans have higher blood pressure variability than women and European Americans. Apart from these ethnicity and sex effects, blood pressure variability increases with increases in age (especially in men), ambulatory blood pressure mean values and adiposity as well as decreased socioeconomic status.

The clinical spectrum of labile hypertension: a management dilemma

J Clin Hypertens (Greenwich). 2009;11:491-497. (c)2009 Wiley Periodicals, Inc.Although the management of the labile component of blood pressure elevation is a problem often encountered by clinicians, there is a paucity of information available to guide therapeutic decisions. This review discusses the clinical relevance of blood pressure lability, the limitations of current knowledge, and possible directions for future research and clinical management.

Masked hypertension: evaluation, prognosis, and treatment

Blood pressure (BP) may be high during usual daily life in one out of 7-8 individuals with normal BP in the clinic or doctor's office. This condition is usually defined as masked hypertension (MH). Prevalence of MH varied across different studies depending on patient characteristics, populations studied, and different definitions of MH. Self-measured BP and ambulatory BP (ABP) have been widely used to identify subjects with MH. Various factors have been identified as possible determinants of MH. Cigarette smoking, alcohol, physical activity, job, and psychological stress may increase BP out of the clinical environment in otherwise normotensive individuals, leading to MH. In most studies, target organ damage was comparable in subjects with MH and those with sustained hypertension, and greater than in those with true normotension. Subjects with MH showed a 1.5- to 3-fold higher risk of major cardiovascular (CV) disease than those with normotension, and their risk was not different from that of patients with sustained hypertension. In an overview of literature, we found that the risk of major CV disease was higher in subjects with MH than in the normotensive subjects regardless of the definition of MH based on self-measured BP (hazard ratio (HR) 2.13; 95% confidence interval (CI): 1.35-3.35; P = 0.001) or 24-h ABP (HR 2.00; 95% CI: 1.54-2.60; P < 0.001). MH is an insidious and prognostically adverse condition that can be reliably diagnosed by self-measured BP and ABP. MH should be searched for in subjects who appear to be more likely to have this condition. Antihypertensive treatment is envisaged in these subjects, although the associated outcome benefits are still undetermined.

Causal mechanisms of masked hypertension: socio-psychological aspects

The contribution of Dr Thomas Pickering's study to the measurement of blood pressure (BP) is the defining aspect of his academic career and achievement - narrowly defined. In this regard, two important areas characterized his study as it relates to masked hypertension. First, he introduced the term, masked hypertension, to replace the rather inappropriate term 'reverse white-coat hypertension' and 'white-coat normotension'; thus drawing attention to the fact that these patients are genuinely hypertensive by ambulatory BP but were missed by normal office BP. More importantly, he rightly maintained that masked hypertension is a true continuum of sustained hypertension rather than an aberrant measurement artifact. Second, is his pivotal study on the important role of psychosocial factors as a potential mechanism for the development of masked hypertension. In this regard, he explained masked hypertension as a conditioned response to anxiety in office settings, and highlighted the role that diagnostic labeling plays in its development. His view of masked hypertension is that of a continuum from prehypertension (based on office BP measurement) to masked hypertension (based on ambulatory BP) and finally to sustained hypertension (based on both office and ambulatory BP). He strongly believes that it is the prehypertensive patients who progress to masked hypertension. Subsequently, patients who are prehypertensive should be screened for masked hypertension and treated. In this manuscript, we summarize his study as it relates to the definition of masked hypertension, the psychosocial characteristics, mechanisms and its clinical relevance.

Traffic-related air pollution and blood pressure in elderly subjects with coronary artery disease

BACKGROUND

Associations between blood pressure (BP) and ambient air pollution have been inconsistent. No studies have used ambulatory BP monitoring and outdoor home air-pollutant measurements with time-activity-location data. We address these gaps in a study of 64 elderly subjects with coronary artery disease, living in retirement communities in the Los Angeles basin.

METHODS

Subjects were followed up for 10 days with hourly waking ambulatory BP monitoring (n = 6539 total measurements), hourly electronic diaries for perceived exertion and location, and real-time activity monitors (actigraphs). We measured hourly outdoor home pollutant gases, particle number, PM2.5, organic carbon, and black carbon. Data were analyzed with mixed models controlling for temperature, posture, actigraph activity, hour, community, and season.

RESULTS

We found positive associations of systolic and diastolic BP with air pollutants. The strongest associations were with organic carbon (especially its estimated fossil-fuel- combustion fraction), multiday average exposures, and time periods when subjects were at home. An interquartile increase in 5-day average organic carbon (5.2 microg/m) was associated with 8.2 mm Hg higher mean systolic BP (95% confidence interval = 3.0-13.4) and 5.8 mm Hg higher mean diastolic BP (3.0-8.6). Associations of BP with 1-8 hour average air pollution were stronger with reports of moderate to strenuous physical exertion but not with higher actigraph motion. Associations were also stronger among 12 obese subjects.

CONCLUSIONS

Exposure to primary organic components of fossil fuel combustion near the home were strongly associated with increased ambulatory BP in a population at potential risk of heart attack. Low fitness or obesity may increase the effects of pollutants.

The day-night difference of blood pressure is increased in AT(1A)-receptor knockout mice on a high-sodium diet

BACKGROUND

Abnormal circadian variation of blood pressure (BP) increases cardiovascular risk. In this study, we examined the influence of angiotensin AT(1A) receptors on circadian BP variation, and specifically on its behavioral activity-related and -unrelated components.

METHODS

BP and locomotor activity were recorded by radiotelemetry in AT(1A)-receptor knockout mice (AT(1A)(-/-)) and their wild-type controls (AT(1A)(+/+)) placed on a normal-salt diet (NSD) or high-salt diet (HSD, 3.1% Na).

RESULTS

The 24-h BP was lower in AT(1A)(-/-) than AT(1A)(+/+) mice on a NSD (92 +/- 2 and 118 +/- 2 mm Hg, respectively), whereas the day-night BP difference (DeltaDNBP) was similar between groups (11 +/- 2 and 12 +/- 1 mm Hg, respectively). HSD increased BP by 20 +/- 2 mm Hg and DeltaDNBP by 7 +/- 1 mm Hg in AT(1A)(-/-) mice, without affecting these parameters much in AT(1A)(+/+) mice. The DeltaDNBP increase in AT(1A)(-/-) mice was caused by nondipping BP during the inactive late-dark period. Conversely, BP rise associated with circadian behavioral activation during the early dark period was not altered by HSD in AT(1A)(-/-) mice. The BP change associated with spontaneous ultradian activity-inactivity bouts was also similar between strains on HSD as was the BP rise associated with induced (cage-switch) behavioral activity. Ganglionic or alpha(1)-adrenergic blockade decreased BP in both strains; HSD did not affect this response in AT(1A)(-/-), but abolished it in AT(1A)(+/+) mice.

CONCLUSIONS

AT(1A)-receptor deficiency, when combined with HSD, can increase circadian BP difference in mice. This increase is mediated principally by activity-unrelated factors, such as the nonsuppressibility of basal resting sympathetic tone by HSD, thus suggesting a form of salt-/volume-dependent hypertension.

Role of Angiotensin II Type 1A Receptors in Cardiovascular Reactivity and Neuronal Activation After Aversive Stress in Mice

We determined whether genetic deficiency of angiotensin II Type 1A (AT 1A ) receptors in mice results in altered neuronal responsiveness and reduced cardiovascular reactivity to stress. Telemetry devices were used to measure mean arterial pressure, heart rate, and activity. Before stress, lower resting mean arterial pressure was recorded in AT 1A −/− (85±2 mm Hg) than in AT 1A +/+ (112±2 mm Hg) mice; heart rate was not different between groups. Cage-switch stress for 90 minutes elevated blood pressure by +24±2 mm Hg in AT 1A +/+ and +17±2 mm Hg in AT 1A −/− mice ( P <0.01), and heart rate increased by +203±9 bpm in AT 1A +/+ and +121±9 bpm in AT 1A −/− mice ( P <0.001). Locomotor activation was less in AT 1A −/− (3.0±0.4 U) than in AT 1A +/+ animals (6.0±0.4 U), but differences in blood pressure and heart rate persisted during nonactive periods. In contrast to wild-type mice, spontaneous baroreflex sensitivity was not inhibited by stress in AT 1A −/− mice. After cage-switch stress, c-Fos immunoreactivity was less in the paraventricular ( P <0.001) and dorsomedial ( P =0.001) nuclei of the hypothalamus and rostral ventrolateral medulla ( P <0.001) in AT 1A −/− compared with AT 1A +/+ mice. Conversely, greater c-Fos immunoreactivity was observed in the medial nucleus of the amygdala, caudal ventrolateral medulla, and nucleus of the solitary tract ( P <0.001) of AT 1A −/− compared with AT 1A +/+ mice. Greater activation of the amygdala suggests that AT 1A receptors normally inhibit the degree of stress-induced anxiety, whereas the lesser activation of the hypothalamus and rostral ventrolateral medulla suggests that AT 1A receptors play a key role in autonomic cardiovascular reactions to acute aversive stress, as well as for stress-induced inhibition of the baroreflex.

Exclusion of Influence of Physical Activity on Ambulatory Blood Pressure

OBJECTIVE

The basal blood pressure (BP) is more intimately related to hypertension severity than casual BP. BP values obtained by ambulatory blood pressure monitoring (ABPM) tend to be influenced by patients' physical activity because values are not always obtained with the patient at rest. The purpose of this study was to estimate the influence of physical activity on BP and determine daytime BP adjusted for activity as measured by ABPM.

METHODS

This study targeted three clinically different groups: healthy medical students (HS, n = 40), patients with hypertension (HT, n = 20), and patients with diabetes mellitus (DM, n = 7). The subjects' BP, heart rate (HR), and physical activity level were measured by a noninvasive portable multi-biomedical recorder. To identify the influence of physical activity on BP in the three study groups, a least squares regression analysis of the relation between BP and ACT (an index of activity with acceleration) was performed for each group.

RESULTS

ACT had a positive influence on systolic BP (SBP) in the HS, HT, and DM groups (R2 = 0.319, 0.576, 0.697, respectively). SBP adjusted for ACT (walking level) by means of the regression model with dummy variable was 0-24 mmHg lower than the value of SBP measured by ABPM, and daytime SBP (walking level) was overestimated by approximately 10 mmHg in comparison to the value of SBP at rest (ACT = 0).

CONCLUSION

Physical activity had a positive effect on SBP. The results showed that physical activity (walking-level) had a positive effect on SBP of about 10 mmHg.

Ambulatory blood pressure and physical activity in heart failure

This observational study used repeated measures over 24 hr to investigate ambulatory blood pressure (BP) and physical activity (PA) profiles in community-based individuals with heart failure (HF). The aims were to (a) compare BP dipping and PA between two groups of HF patients with different functional statuses, and (b) determine whether the strength of the association between ambulatory BP and PA varies by functional status in HF. Ambulatory BP was measured every 30 min with a SpaceLabs 90207; a Basic Motionlogger actigraph was used to measure PA minute-by-minute. Fifty-six participants (54% female, age 66.96 + or - 12.35 years) completed data collection. Functional status was based on New York Heart Association (NYHA) ratings. Twenty-seven patients had no limitation of PA (NYHA Class I HF), whereas 29 had some limitation of PA but no discomfort at rest (NYHA Class II or III HF). Patients with Class I HF had a significantly greater degree of BP dipping than those with Class II/III HF after controlling for left ventricular ejection fraction. In a mixed-model analysis, PA was significantly related to ambulatory systolic and diastolic BP and mean arterial pressure. The strength of the association between PA and BP was not significantly different for the two groups of patients. These findings demonstrate differences between Class I and Class II/II HF in BP dipping status and ambulatory BP but not PA. Longitudinal research is recommended to improve understanding of the influence of disease progression on changes in 24-hr PA and BP profiles of patients with HF.

Blood pressure reactivity to emotional stress is reduced in AT1A-receptor knockout mice on normal, but not high salt intake

Pharmacological evidence suggests that angiotensin II type 1 (AT(1)) receptors are involved in the regulation of cardiovascular response to emotional stress and reinforcing effect of dietary salt on this response. In this study, we examined the effect of genetic deletion of AT(1A) receptors on the cardiovascular effects of stress and salt in mice. AT(1A) receptor knockout (AT(1A)(-/-)) and wild-type (AT(1A)(+/+)) mice were implanted with telemetry devices and placed on a normal (0.4%) or high (3.1%) salt diet (HSD). Resting blood pressure (BP) in AT(1A)(-/-) mice (84+/-3 mm Hg) was lower than in AT(1A)(+/+) mice (107+/-2 mm Hg). Negative emotional (restraint) stress increased BP by 33+/-3 mm Hg in AT(1A)(+/+) mice. This response was attenuated by 40% in AT(1A)(-/-) mice (18+/-3 mm Hg). Conversely, the BP increase caused by food presentation and feeding was similar in AT(1A)(-/-) (25+/-3 mm Hg) and AT(1A)(+/+) mice (26+/-3 mm Hg). HSD increased resting BP by 14+/-4 mm Hg in AT(1A)(-/-) mice without affecting it significantly in AT(1A)(+/+) mice. Under these conditions, the pressor response to restraint stress in AT(1A)(-/-) mice (30+/-3 mm Hg) was no longer different from that in wild-type animals (28+/-3 mm Hg). The BP response to feeding was not altered by HSD in either AT(1A)(-/-) or AT(1A)(+/+) mice (25+/-2 and 27+/-3 mm Hg, respectively). These results indicate that AT(1A) receptor deficiency leads to a reduction in BP reactivity to negative emotional stress, but not feeding. HSD can selectively reinforce the cardiovascular response to negative stress in AT(1A)(-/-) mice. However, there is little interaction between AT(1A) receptors, excess dietary sodium and feeding-induced cardiovascular arousal.

Masked hypertension in diabetes mellitus: a potential risk

The prevalence and clinical significance of masked hypertension (MHT) in diabetics have infrequently been described. The authors assessed the association of MHT (defined using a clinic blood pressure [BP] <140/90 mm Hg and daytime ambulatory BP > or = 135/85 mm Hg) with microvascular and macrovascular end organ damage in 81 clinically normotensive Japanese diabetic persons. The prevalence of silent cerebral infarcts (SCIs), increased left ventricular mass, and albuminuria were evaluated. Of 81 patients, 38 (46.9%) were classified as having MHT and showed significantly more SCIs (mean +/- SE: 2.5+/-0.5 vs 1.1+/-0.2; P=.017), and more albuminuria (39% vs 16%; P=.025), but no increase in left ventricular mass index, than the normotensive persons in office and on ambulatory BP monitoring group. The prevalence of MHT in this diabetic population was high (47%). Diabetic patients with MHT showed evidence of brain and kidney damage. Hence, out-of-office monitoring of BP may be indicated in diabetics whose BP is normal in the clinic.

High Job Strain and Ambulatory Blood Pressure in Middle-Aged Men and Women From the Belgian Job Stress Study

OBJECTIVE

The aim of this study was to assess whether job strain is associated with 24-hour ambulatory blood pressure measurements within a subsample of the Belgian Job Stress Project (BELSTRESS) population.

METHODS

A group of 89 middle-aged male and female workers perceiving high job strain and an equally large group of workers perceiving no high job strain wore an ambulatory blood pressure monitor for 24 hours on a regular working day.

RESULTS

Mean ambulatory blood pressure at work, at home, and while asleep was significantly higher in workers with job strain as compared with others. The associations between job strain and ambulatory blood pressure were independent from the covariates.

CONCLUSIONS

Within this study, high job strain was an important independent risk factor for higher ambulatory blood pressure at work, at home, and during sleep in a group of men and women.

Reactivity of Ambulatory Blood Pressure to Physical Activity Varies With Time of Day

Blood pressure (BP) fluctuates over a 24-hour period, but it is unclear to what extent this variation is governed completely by changes in physical activity. Our aim was to use a BP “reactivity index” to investigate whether the BP response to a given level of physical activity changes during a normal sleep-wake cycle. Hypertensive patients (n=440) underwent simultaneous 24-hour ambulatory BP, heart rate (HR), and activity monitoring. BP and HR were measured every 20 minutes. Actigraphy data were averaged over the 15 minutes that preceded a BP measurement. Individual BP and HR reactivity indices were calculated using least-squares regression for twelve 2-hour periods. These indices were then analyzed for time-of-day differences using a general linear model. Systolic BP and HR were generally more reactive to physical activity than diastolic BP. The highest reactivity of systolic BP (mean±SE=4±1 mm Hg per logged unit change in activity) was observed between 8:00 am and 10:00 am ( P =0.014). Between 10:00 am and 12:00 pm , BP reactivity then decreased ( P =0.048) and showed a secondary rise in the early afternoon. These 24-hour changes in BP reactivity did not differ significantly between groups formed on the basis of early and late wake times ( P =0.485), medication use, age, and sex ( P >0.350). In conclusion, under conditions of normal living, the reactivity of BP and HR to a given unit change in activity is highest in the morning and shows a secondary rise in the afternoon.

Haemodynamic responses to physical activity and body posture during everyday life

OBJECTIVE

To determine the relationships between body posture and physical activity and systemic haemodynamics during everyday life.

METHODS

Continuous measurements were performed in 34 subjects (16 hypertensive, 12 male), aged 49 +/- 13 (mean +/- standard deviation) years. Blood pressure (BP) was measured in the brachial artery. Physical activity and posture were measured with four accelerometers. Beat-to-beat values of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were computed from the pressure waveforms. Multiple correlation coefficients (R) between activity and haemodynamic variables were computed and responses to physical activity were estimated with random regression models.

RESULTS

The overall percentages of variance in SBP, DBP, HR, SV, CO and SVR explained by activity (R2) were 32, 28, 56, 44, 74, and 45%, respectively. The SBP and HR increased linearly with increasing levels of activity (19 mmHg and 30 beats/min when activity increased 90 percentiles). Other variables showed parabolic relationships. The initial decrease in SV and CO (14 ml and 0.5 l/min) and increase in DBP and SVR (9 mmHg and 2 mmHg min/l) with increasing levels of activity coincided with changes in posture (lying-sitting-standing). The subsequent SV and CO increase (23 ml and 3.7 l/min) and DBP and SVR decrease (8 mmHg and 8 mmHg min/l) coincided with changes in activity (standing-moving generally-walking).

CONCLUSIONS

Our findings show that normal daily posture and activity are only moderate determinants of BP, but main determinants of HR and CO variation.

Systolic blood pressure variability as a risk factor for stroke and cardiovascular mortality in the elderly hypertensive population

OBJECTIVE

To investigate whether baseline systolic blood pressure variability was a risk factor for stroke, cardiovascular mortality or cardiac events during the Syst-Eur trial.

DESIGN

The Syst-Eur study was a randomized, double-blind, placebo-controlled trial, powered to detect differences in stroke rate between participants on active antihypertensive treatment and placebo. Systolic blood pressure variability measurements were made on 744 participants at the start of the trial. Systolic blood pressure variability was calculated over three time frames: 24 h, daytime and night-time. The placebo and active treatment subgroups were analysed separately using an intention-to-treat principle, adjusting for confounding factors using a multiple Cox regression model.

PARTICIPANTS

An elderly hypertensive European population.

MAIN OUTCOME MEASURES

Stroke, cardiac events (fatal and non-fatal heart failure, fatal and non-fatal myocardial infarction and sudden death) and cardiovascular mortality (death attributed to stroke, heart failure, myocardial infarction, sudden death, pulmonary embolus, peripheral vascular disease and aortic dissection).

RESULTS

The risk of stroke increased by 80% (95% confidence interval: 17-176%) for every 5 mmHg increase in night-time systolic blood pressure variability in the placebo group. Risk of cardiovascular mortality and cardiac events was not significantly altered. Daytime variability readings did not predict outcome. Antihypertensive treatment did not affect systolic blood pressure variability over the median 4.4-year follow-up.

CONCLUSION

In the placebo group, but not the active treatment group, increased night-time systolic blood pressure variability on admission to the Syst-Eur trial was an independent risk factor for stroke during the trial.

The Effects of Physical Activity and Autonomic Nerve Tone on the Daily Fluctuation of Blood Pressure

The effects of daily activity and autonomic nerve tone on the fluctuation of ambulatory blood pressure were studied in hypertensive patients. The autonomic nerve tone was measured by frequency domain analysis of the RR interval. Physical activity was evaluated by a walk count, converted to a walk rate (WR), recorded using a digital Holter ECG fitted with an accelerometer, with simultaneous monitoring of blood pressure (Bp). Average values of the WR, H and L/H components were calculated for the 15 min. period just prior to Bp monitoring. The relationship between the average WR, H and L/H values and the Bp was determined by a linear regression analysis. Hypertension was classified into three types, autonomic nerve dominant (AN), exercise dominant (EX), and irregular (IR), based on a high correlation coefficient between Bp and either H or L/H (AN type), between Bp and WR (EX type), or no significant correlation between Bp and any of the parameters (IR type). Of the thirty hypertensive patients studied 11 were classified as AN, 12 as EX, and 7 as IR. Patients of the EX type had significantly lower Bp than patients in the other two classes. Furthermore, all of the IR type patients showed non-dipper type hypertension, suggesting that the Bp regulation mechanisms were impaired. The results suggest the significance of simultaneous monitoring of physical activity and autonomic nerve function at the time of Bp monitoring.

Non-random fluctuations and multi-scale dynamics regulation of human activity

We investigate if known extrinsic and intrinsic factors fully account for the complex features observed in recordings of human activity as measured from forearm motion in subjects undergoing their regular daily routine. We demonstrate that the apparently random forearm motion possesses dynamic patterns characterized by robust scale-invariant and nonlinear features. These patterns remain stable from one subject to another and are unaffected by changes in the average activity level that occur within individual subjects throughout the day and on different days of the week, since they persist during daily routine and when the same subjects undergo time-isolation laboratory experiments designed to account for the circadian phase and to control the known extrinsic factors. Further, by modeling the scheduled events imposed throughout the laboratory protocols, we demonstrate that they cannot account for the observed scaling patterns in activity fluctuations. We attribute these patterns to a previously unrecognized intrinsic nonlinear multi-scale control mechanism of human activity that is independent of known extrinsic factors such as random and scheduled events, as well as the known intrinsic factors which possess a single characteristic time scale such as circadian and ultradian rhythms.

Ambulatory blood pressure monitoring in children and adolescents

With recent technological advances, 24-hour ambulatory blood pressure (BP) monitoring (ABPM) has become a useful tool for the evaluation, diagnosis, and management of hypertensive children. It provides a more accurate representation of an individual's BP rather than intermittent casual or office BP measurements. Hence, ABPM is being used more often to assess the BP of children. In this comprehensive review, we provide the reader with the available literature on ABPM, discuss the advantages and limitations of ABPM, and the interpretation of ABPM data. The role of ABPM in various clinical conditions and hypertension research in children is presented.

Determinants of ambulatory blood pressure response to physical activity

OBJECTIVES

Previous studies reported that the association between physical activity, measured with a wrist-worn accelerometer, and ambulatory blood pressure is rather weak and that the inter-individual variation in the degree of association is high. The aim of the present study was to quantify the responses of ambulatory blood pressure (BP) and heart rate (HR) to physical activity, and to determine the effect of age, gender, body mass index, mean BP and HR level and the use of antihypertensive medication on these responses.

PATIENTS AND METHODS

Twenty-seven subjects (24 hypertensive) underwent 24-h ambulatory monitoring of BP, HR and physical activity. Physical activity was measured with four accelerometers mounted on the trunk and legs. The daytime BP and HR responses to physical activity and the possible modulating effects of the various subject characteristics on these responses were estimated with Random Regression Models.

RESULTS

Increasing physical activity from a very low level (e.g. watching television) to a moderate level (e.g. shopping) caused an average response of systolic blood pressure (SBP) of 11.6 mmHg, of diastolic blood pressure (DBP) of 7.0 mmHg and of HR of 16.1 beats/min. The SBP response to activity was about 2 mmHg larger for the overweight subjects than for subjects with normal weight, and the SBP, DBP and HR responses increased about 0.8 mmHg, 0.6 mmHg and 0.7 beats/min, respectively, with every 10 years increase in age. The between-subjects variances in estimated responses were low and were almost completely explained by differences in overweight and age between subjects. The average within-subject variances, however, were high.

CONCLUSIONS

Normal daily physical activity explains only a small part of the BP and HR variability. The BP and HR responses to activity are modestly affected by age. Overweight has a small effect on the SBP response to activity.

The white-coat effect is associated with increased blood pressure reactivity to physical activity

OBJECTIVE

The aim of this study was to test the hypothesis that blood pressure (BP) reactivity to the stress of a clinic visit, the so-called white-coat effect, is associated with increased BP reactivity to physical activity.

DESIGN

Patients referred to our clinic for assessment of hypertension prospectively underwent 24-h ambulatory BP monitoring and simultaneous actigraphy.

METHODS

The difference between mean clinic BP and mean daytime ambulatory BP was considered to be a measure of the white-coat effect. Presence or absence of a white-coat effect (clinic-daytime difference > 0 mmHg) was added to a mixed model regression of BP on mean activity score for the 10-min interval preceding BP measurement.

RESULTS

The group (n = 421) was heterogeneous in age, gender, mean 24-h BP and use of antihypertensive medications. A total of 259 patients had a systolic white-coat effect; for diastolic BP there were 264. Female patients exhibited a significantly larger white-coat effect. Coefficients for the regressions of both systolic and diastolic blood pressure on physical activity levels were significantly higher in those who had a white-coat effect.

CONCLUSIONS

These data suggest increased BP reactivity to activity in those with a white-coat effect. Patients with a prominent white-coat effect may experience greater BP load during normal daily activities as a consequence of increased BP reactivity. In patients with white-coat hypertension, this may contribute to target-organ damage.

The morning surge in blood pressure and heart rate is dependent on levels of physical activity after waking

OBJECTIVE

To define the influence of morning physical activity levels on the magnitude of the morning surge in blood pressure and heart rate.

DESIGN AND METHODS

Blood pressure and physical activity were simultaneously recorded in 420 patients by 24-h monitor and actigraphy. The morning surge was defined as the difference between mean blood pressure and heart rate values in the 4-h periods before and after waking; the trough-to-peak surge in blood pressure was also calculated. These values were regressed on the difference in mean (log transformed) physical activity for the same two periods. The analysis was adjusted for covariates, including age, sex, clinic blood pressure and use of antihypertensive medication, in a multiple linear regression.

RESULTS

The mean morning surges in blood pressure and heart rate were 23/15(+/- 13/10) mmHg and 17(+/- 10) beats/min, respectively. The geometric mean increase in physical activity after waking was 33(+/- 1.5) units. The magnitudes of the morning surge in systolic blood pressure, diastolic blood pressure and heart rate were all significantly and positively correlated with the difference in mean physical activity before and after waking (P < 0.005). Greater clinic blood pressure was significantly associated with a greater morning surge in blood pressure on physical activity (P < 0.0005).

CONCLUSIONS

The magnitude of the morning surge is significantly associated with the level of physical activity in the hours after waking. Physical activity should be taken into account when the results of ambulatory blood pressure monitoring are interpreted.

Exercise and hypertension

Epidemiologic studies have consistently revealed inverse associations between physical activity (or fitness) and hypertension. There are hypotensive benefits to exercise training found across a number of aerobic and progressive resistance training modalities. Optimal exercise prescriptions remain unclear, but hypotensive benefits have been noted for mild to vigorous ranges of exercise intensity, for as few as three exercise sessions per week and durations as short as 20 minutes. Hypertensive subjects appear to experience greater reductions than normotensive subjects. Exercise interventions may be safely and effectively used with mild to moderate as well as severe levels of hypertension. The incorporation of physical activity with other lifestyle interventions provides multiple benefits to hypertensive patients that extend beyond a reduction in blood pressure.

The beta blockers: are they as protective in hypertension as in other cardiovascular conditions?

Beta blockers are frequently used to treat hypertension because of their well established safety and efficacy. Large clinical trials yield a 12%--20% decline in cardiovascular end points in hypertensive patients treated with beta blockers. However, beta blockers account for only 11% of antihypertensive prescriptions, and their use appears to be declining as newer agents with fewer side effects become available. The metabolic side effects of beta blockers have recently been examined. While they may raise triglycerides, lower high-density lipoprotein cholesterol, induce glucose intolerance, and possibly unmask diabetes, these effects have not been shown to impact their clinical effectiveness. For hypertension, beta blockers are still recommended as first-line therapy in many patients, particularly those at high risk for cardiovascular disease. They are also indicated for other cardiovascular disorders, such as congestive heart failure and postmyocardial infarction, in which mortality reductions exceed that seen with hypertension treatment in patients without cardiovascular complications. (c)2001 Le Jacq Communications, Inc.