Optimal definition of daytime and night-time blood pressure

OBJECTIVE: To review and categorize methods to define daytime and night-time blood pressures and to propose an optimal definition. METHODS: The methods can be divided into clock-time-independent and clock-time-dependent methods and, in addition, into wide methods, which use all pressure measurements for the entire 24 h period, and narrow methods, which exclude some of the measurements. RESULTS: The asleep and awake blood pressures, mostly defined as the in-bed and out-of-bed blood pressures, can be considered the optimum standard. Wide (square-wave fitting) and narrow (cumulative-sum analysis) clock-time-independent methods perform well with most subjects, but are problematic with reverse dippers because they identify periods of high and low blood pressure in these subjects that do not coincide with the day and the night. The results from fixed-time methods deviate from the awake and asleep blood pressures whens the predefined times do not coincide with the times subjects go to bed and arise; this is less of a problem for the narrow methods, in which data from morning and evening transition periods are discarded, than it is for the rigid time schedules of the wide methods. Reproducibilities of the various methods are roughly similar. CONCLUSION: We suggest that the optimal definition of daytime and night-time blood pressure is provided by the narrow clock-time-dependent method, in which data from morning and evening transition periods are excluded, because it is simple, reasonably accurate and reproducible and can be applied without disruption of the living habits of most subjects.     

Comparison of coronary microcirculation in female nurses after day-time versus night-time shifts

Nightshift work, which is known to cause mental stress and disrupt normal biological diurnal rhythms, leads to endothelial dysfunction resulting in increased risk for cardiovascular disease. This study aimed to investigate the acute effect of night-shift work on coronary microcirculation through assessment of coronary flow reserve (CFR) by transthoracic Doppler echocardiography. This study consisted of 36 women nurses who underwent transthoracic Doppler echocardiographic examinations after working a nightshift and on a regular day without previous nightshift work. Flow velocity in the distal portion of the left anterior descending coronary artery was measured at baseline and during adenosine infusion. CFR was calculated as the ratio of hyperemic to basal mean diastolic flow velocity. CFR after night work was lower than that on a regular workday (3.8 ± 0.6 vs 4.1 ± 0.6, p <0.001). Degree of decreases in CFR after night work was correlated to Framingham risk score (r = 0.35, p = 0.036). In conclusion, this study demonstrated that coronary microcirculation was impaired after nightshift work in women nurses.     

24-h blood pressure monitoring in normal tension glaucoma: night-time blood pressure variability

Systemic arterial hypotension, hypertension and altered ocular blood flow are known risk factors in glaucoma. In this study, 24-h ambulatory blood pressure monitoring was performed in patients with normal tension glaucoma (NTG) and controls to evaluate blood pressure variability. In all, 51 patients with NTG and 28 age-matched controls were included in this prospective study. A 24-h ambulatory blood pressure monitoring (SpaceLabs Medical Inc., Redmond, USA) was performed and systolic, diastolic and mean arterial blood pressures were measured every 30 min during daytime (0800-2000) and night time (0000-0600). To evaluate blood pressure variability a variability index was defined as the s.d. of blood pressure measurements. Night-time blood pressure depression ('dip') was calculated (in percent of the daytime blood pressures). Patients with NTG exhibited higher night-time diastolic (P = 0.01) and mean arterial blood pressure values (P = 0.02) compared to controls, whereas systolic blood pressure data were not significantly different. The variability indices of night-time systolic, diastolic and mean arterial blood pressure measurements were significantly increased in patients with NTG compared to controls (P < 0.05). The night-time blood pressure depression of systolic (P = 0.47), diastolic (P = 0.11) and mean arterial blood pressures (P = 0.28) was not significantly different between patients with NTG and controls. In conclusion, patients with NTG showed increased variability of night-time blood pressure measurements compared to controls. Increased fluctuation of blood pressure may lead to ocular perfusion pressure fluctuation and may cause ischaemic episodes at the optic nerve head.     

Ethnic differences in sleep quality accompany ethnic differences in night-time blood pressure dipping

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Sleep quality accompanied ethnic differences in systolic and diastolic BP dipping, but did not account for these differences.     

Classification of blood pressure levels by ambulatory blood pressure in hypertension

Whereas clinic blood pressure (CBP) above normality is divided into stages, no corresponding classifications are available for 24-hour ambulatory blood pressure (ABP). We conducted a study (1) to define stages of hypertension by ABP corresponding to CBP stages and (2) to evaluate if these stages have prognostic impact similar to CBP stages. Seven hundred thirty-six hypertensive patients were included. Mean systolic blood pressure was 149+/-15.2/87+/-8.6 mm Hg for CBP and 135+/-13/79+/-9.7 mm Hg for ABP. The mean bias between both methods was -13.3 mm Hg (95% CI, -14.3 to -12.2; 1.96xSD limits of agreement, 15.7 to -42.3) and -7.3 mm Hg (95% CI, -7.9 to -6.6; 1.96xSD limits of agreement, 9.8 to -24.3) for systolic and diastolic blood pressure (P>0.0001 for both), respectively. Classification of hypertension by ABP revealed lower cutoff values for the different stages of hypertension compared with the corresponding cutoff values for CBP (CBP versus ABP: 140/90 versus 132/81 mm Hg; 160/100 versus 140/88 mm Hg; 180/110 versus 148/94 mm Hg, P<0.001). Overall, 82 (11.1%) patients had nonfatal clinical cardiovascular events and 9 (1.2%) patients died of a cardiovascular cause during follow-up. The distribution of cardiovascular events was significantly associated with increasing ABP value (P<0.006). Staging of hypertension by ABP may facilitate the use of this method in daily clinical practice, as ABP can now be used not only to confirm the diagnosis of hypertension but also to assess the severity and prognosis of hypertensive disease.     

Acute effects of night-time noise exposure on blood pressure in populations living near airports.

AIMS: Within the framework of the HYENA (hypertension and exposure to noise near airports) project we investigated the effect of short-term changes of transportation or indoor noise levels on blood pressure (BP) and heart rate (HR) during night-time sleep in 140 subjects living near four major European airports. METHODS AND RESULTS: Non-invasive ambulatory BP measurements at 15 min intervals were performed. Noise was measured during the night sleeping period and recorded digitally for the identification of the source of a noise event. Exposure variables included equivalent noise level over 1 and 15 min and presence/absence of event (with LAmax > 35 dB) before each BP measurement. Random effects models for repeated measurements were applied. An increase in BP (6.2 mmHg (0.63-12) for systolic and 7.4 mmHg (3.1, 12) for diastolic) was observed over 15 min intervals in which an aircraft event occurred. A non-significant increase in HR was also observed (by 5.4 b.p.m.). Less consistent effects were observed on HR. When the actual maximum noise level of an event was assessed there were no systematic differences in the effects according to the noise source. CONCLUSION: Effects of noise exposure on elevated subsequent BP measurements were clearly shown. The effect size of the noise level appears to be independent of the noise source.     

The effects of short-term blood pressure variability and nighttime blood pressure levels on cognitive function.

We investigated the relationship between 24-h blood pressure (BP) and cognitive function. We performed the Hasegawa Dementia Scale Revised (HDSR), the Mini-Mental State Examination (MMSE), and the Raven's Coloured Progressive Matrices Test (RCPM) in 88 subjects (71+/-9 years) with no history of stroke. Ambulatory BP was non-invasively measured using a TM2421 for 24 h in all patients. Whereas 90% of the scores converged into a narrow range between 25 and 30 points in the HDSR and the MMSE tests, the RCPM score was widely distributed, ranging from 9 to 36 points. The subjects were therefore divided into three groups of > or =25, 26-30, and 31-36 according to their RCPM scores. Subjects with lower scores were significantly associated with increased short-term BP variability during the daytime (p<0.05) and had a tendency toward higher nighttime SBP (p=0.05) compared with those with higher scores. Increased short-term variability of daytime BP and high nighttime systolic BP were associated with cognitive impairment as assessed by the RCPM. The RCPM, which can assess the capacity for judgment through visual information processing, may detect earlier stages of cognitive impairment related to high BP. To prevent a deterioration of cognitive function, strict control of nighttime BP and suppression of short-term BP variability are thus necessary.     

Plasma brain natriuretic peptide levels and blood pressure tracking in the Framingham Heart Study

Increased brain natriuretic peptide (BNP) expression in the ventricles antedates elevated blood pressure (BP) in experimental studies. We hypothesized that higher plasma BNP levels in nonhypertensive individuals may be associated with a greater likelihood of future BP increase and/or hypertension. We evaluated the relations of plasma BNP to longitudinal BP tracking and incidence of hypertension in 1801 nonhypertensive Framingham Heart Study participants (mean age, 56 years; 57% women) by using gender-specific multivariable logistic regression. Progression of BP stage was defined as an increment of one or more BP categories, as classified by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI). Hypertension was defined as a systolic BP > or =140 or diastolic BP > or =90 mm Hg or use of antihypertensive medications. On follow-up 4 years from baseline, progression of BP category was observed in 36.2% of men and 33.1% of women; hypertension developed in 16.4% of men and 15.5% of women. In multivariable models adjusting for known risk factors, elevated plasma BNP level was associated with increased risk of BP progression in men (odds ratio of 1.15 for trend across categories, P=0.046) but not in women (P=0.82). There were no significant trends of increasing incidence of hypertension across BNP categories in men or women. In our community-based sample, higher plasma BNP levels were associated with increased risk of BP progression in men but not women. Additional investigations are warranted to confirm these findings and elucidate the basis for these gender-related differences.     

Short-term representatives of daytime and night-time ambulatory blood pressures.

OBJECTIVE: To see whether measurements of ambulatory blood pressure during short-term daytime and night-time periods can represent complete daytime and night-time pressures accurately. DESIGN: Short-term measurements would be less uncomfortable for patients, easier to perform and could lead to fewer missing values, outliers or artefacts than full-day measurements, especially when repeated monitorings are required. METHOD: Ambulatory blood pressure was measured every 15 min for 24 h in 254 subjects with normal or borderline office blood pressure. Each pressure profile included at least 80 valid readings. Mean blood pressures for different 1-, 2-, 3-, 4-, 5- and 6-h spans were calculated and compared with mean daytime and night-time values using paired Student's t-test. RESULTS: One or two-hour spans of daytime blood pressure poorly represented mean daytime pressure. In contrast, 4-h readings, selected between 1000-2200 h represented daytime blood pressure with good accuracy. Over the total sample, 4-h mean blood pressure readings from 1000-2200 h differed from daytime readings by less than 2 mmHg and 2-h mean readings from 0300-0700 h differed from mean night-time readings by less than 1 mmHg. CONCLUSION: We suggest that 4-h measurements of ambulatory blood pressure during the daytime and 2-h measurements at night (with time spans selected as indicated as above) may be of value.     

Pregnancy hypertension, blood pressure during labor, and blood lead levels

Pregnancy hypertension, blood pressure during labor, and the umbilical cord blood lead concentration were assessed in 3851 women for whom additional demographic, medical, and personal information was available. Lead levels correlated with both systolic (Pearson r = 0.081, p = 0.0001) and diastolic (r = 0.051, p = 0.002) blood pressures during labor. The incidence of pregnancy hypertension increased with lead level. Multivariate models of pregnancy hypertension and systolic blood pressure as a function of maternal age, parity, hematocrit, ponderal index, race, and diabetes were improved by including lead as a predictor variable. At these observed levels of exposure (mean blood lead, 6.9 +/- 3.3 [SD] micrograms/dl), lead appears to have a small but demonstrable association with pregnancy hypertension and blood pressure at the time of delivery, but not with preeclampsia.     

The effects of various definitions of dipping and daytime and night-time on the characterization of 24 h profiles of blood pressure

BACKGROUND: Ambulatory blood pressure monitoring allows characterization of the patient's average blood pressure load as well as various profiles of blood pressure. Results from clinical studies suggest that dippers (patients whose blood pressures decrease during night-time) have a lower risk of cardiovascular events than do nondippers with similar daytime blood pressures. However, the definitions of dipping as well as of daytime and night-time vary among clinical studies. OBJECTIVE: To determine whether various definitions lead to markedly different classifications of dipper status. DESIGN AND METHODS: We analyzed 894 24 h ambulatory blood pressure recordings that had been performed at our institution according to three previously published definitions of daytime and night-time and five definitions of dipping. RESULTS: There were small but statistically significant differences among the mean daytime and night-time blood pressures determined using the various definitions. Likewise, the proportions of dippers varied significantly with definitions of dipping and of daytime and night-time. CONCLUSIONS: Differences among definitions of dipping as well as of daytime and night-time lead to significant variations in the characterization of patients' 24 h blood blood pressure profiles. The results of this analysis can be used when comparing the results of clinical studies as well as in their design.     

中老年正常高值血压水平与冠状动脉性心脏病相关

目的探讨中老年正常高值血压人群血压水平与冠状动脉性心脏病(冠心病)的相关性。方法选取316例50岁以上接受冠状动脉造影检查的正常高值血压者,按照冠状动脉造影结果分为冠心病组(n=129)和非冠心病组(n=187)。对所有对象进行血压、身高、体质量测量,检测血脂指标。结果冠心病组舒张压低于非冠心病组[(73.1±8.9)比(77.0±8.0)mmHg],脉压高于非冠心病组[(55.9±10.5)比(51.2±9.5)mmHg]。对性别、年龄等常见冠心病危险因素调整后,较高的收缩压(≥130mmHg)、较低的舒张压(≤85mmHg)以及较大的脉压(≥60mmHg)与冠心病的发生相关,OR(95%CI)分别为1.60(1.04～2.46)、1.52(1.07～2.16)、1.90(1.06～3.39),均P<0.05。多因素Logistic逐步回归分析发现脉压≥60mmHg是冠心病的独立危险因素。结论在中老年正常高值血压人群中,较高的收缩压、较低的舒张压以及脉压增大与冠心病发生风险相关联,脉压≥60mmHg是冠心病的独立危险因素。     

卡维地洛对降压及血清Ⅲ型前胶原氨基端肽的影响

目的 :观察卡维地洛对原发性高血压 (EH)患者的降压效果及对血清Ⅲ型前胶原氨基端肽 (PⅢNP)及去甲肾上腺素 (NE)、肾上腺素 (E)水平的影响。方法 :EH患者服用卡维地洛治疗 12周 ,观察治疗前后心率、血压及血清PⅢNP及血浆NE、E水平的变化。结果 :EH患者治疗前血压、心率、血清PⅢNP及血浆NE、E水平显著高于正常对照组。治疗 12周后血压、心率、血清PⅢNP及血浆NE、E水平较前显著降低。治疗前后血压与血清PⅢNP水平间无明显相关性。结论 :卡维地洛可以有效控制血压、降低血清PⅢNP及血浆NE、E水平且副作用少 ,卡维地洛降低血压的作用与降低血清PⅢNP水平的作用并非完全一致     

Systolic blood pressure levels and mortality in Australian medical inpatients

The epidemiology of elevations in blood pressure is incompletely characterized, particularly in Australia. Given the lack of evidence regarding the frequency and the optimal management of in-hospital hypertension, the authors performed a multicenter retrospective cohort study of consecutive medical admissions in South Australia over a 2-year period to investigate systolic blood pressure levels and their association with in-hospital mortality. Among 16 896 inpatients, 76% had at least one systolic blood pressure reading of ≥140 mmHg and 11.7% of ≥180 mmHg during hospitalization. A statistically significant negative relationship was observed between having at least one reading ≥140 mmHg and a likelihood of in-hospital mortality (odds ratio 0.41, 95% CI: 0.35 to 0.49, P < .001). Our results suggest that elevations in systolic blood pressure are common in Australian medical inpatients. However, the inverse association observed between systolic blood pressure values ≥140 mmHg and in-hospital mortality warrants further research to determine the clinical significance and optimal management of blood pressure elevations in this group.     

Nocturnal blood pressure during apnoeic and ventilatory periods in patients with obstructive sleep apnoea.

The exact nature of asleep blood pressure in relation to awake blood pressure is still unclear in patients with obstructive sleep apnoea. This study aimed: 1) to investigate the asleep blood pressure in both apnoeic and ventilatory periods; 2) to determine the diurnal and nocturnal factors correlated with the changes in blood pressure from apnoea to ventilatory periods during sleep. Thirty-two patients, newly diagnosed as moderate to severe obstructive sleep apnoea with a standard nocturnal polysomnography, were enrolled. The blood pressure was monitored by using the noninvasive continuous monitoring method during polysomnographic study. The mean blood pressures in ventilatory periods during nonrapid eye movement (NREM) and rapid eye movement (REM) sleep were 117.5+/-17.9 mm Hg and 128.8+/-21.9 mm Hg, and those in apnoea periods were 94.5+/-15.4 mm Hg and 102.7+/-19.0 mm Hg. The average blood pressure during NREM sleep (103.0+/-16.1 mm Hg) was higher than the awake blood pressure (97.0+/-15.7 mm Hg). The blood pressure during REM sleep was greater than that during NREM sleep. The changes in the nocturnal blood pressure from apnoea to ventilatory periods were inversely correlated with the age and nocturnal mean nadir saturation. In conclusion, patients with obstructive sleep apnoea have higher asleep blood pressure than awake blood pressure.