Showing papers by "Robert Fagard published in 1996"

Prediction of the actual awake and asleep blood pressures by various methods of 24 h pressure analysis.

Abstract: ObjectiveTo assess the relationships of daytime and night-time blood pressures and the day-night pressure differences, obtained by various analytical methods, with the actual awake and asleep pressures and the awakeasleep pressure difference.MethodsAmbulatory blood pressure was successfully monitore

Athlete's Heart: A Meta-Analysis of the Echocardiographic Experience

Abstract: Meta-analytical techniques were applied to selected echocardiographic reports on athlete's heart. The combined analysis of studies in which competitive long-distance runners were compared to matched nonathletic control subjects, revealed a 10% (p < 0.001) higher left ventricular internal diameter in the runners, an 18% (p < 0.001) thicker wall and an 8% (p < 0.05) greater relative wall thickness. In strength athletes these differences averaged +2.5% (p < 0.01), +15% (p < 0.05) and +12% (p < 0.05), respectively, and in cyclists +9% (p < 0.05), +29% (p < 0.01) and +19% (p <0.05). When compared to their respective controls, left ventricular mass was larger by 64% (p < 0.01) in cyclists, 48% (p < 0.001) in runners and 25% (p < 0.05) in strength athletes. There were no differences in left ventricular systolic or diastolic function at rest. The meta-analysis of longitudinal studies, in which athletes were assessed in active and inactive periods, suggested that at least part of the differences from nonathletes can be ascribed to the training per se. In conclusion, the classification of left ventricular hypertrophy in athletes as eccentric or concentric has to be considered as a relative concept, most likely related to the fact that training regimens and/or sports activities are not exclusively of the dynamic or static type but comprise both components to a variable extent.

An epidemiological approach to ambulatory blood pressure monitoring:the Belgian Population Study.

Abstract: BACKGROUND: In order to determine reference values for ambulatory blood pressure, a random population sample of 1057 persons, 20-88 years old, was investigated in a geographically defined area of Belgium. This article is the final report on the cross-sectional phase of this population survey. METHODS:Twenty-four-hour ambulatory pressure was recorded at 20 min intervals from 0800 to 2200 h and at 45 min intervals from 2200 to 0800 h. Conventional blood pressure was measured by trained nurses at the participants' homes and also in a subgroup of 532 persons at a locally organized clinic. A conventional blood pressure exceeding 140 mmHg systolic or 90 mmHg diastolic and the taking of antihypertensive drugs were the criteria used to distinguish between normotensive and hypertensive persons. RESULTS: In the 1057 patients, of whom 328 were hypertensive, 24 h, daytime (2200 to 0800 h) and night-time (0000 to 0600 h) pressures averaged 119/71, 125/77 and 108/62 mmHg, respectively. Compared with daytime values, blood pressures at home were 3.5/1.5 mmHg lower in 729 normotensive people but 11.6/4.5 mmHg higher in 328 hypertensive patients. In the normotensive subgroup the 95th percentiles of the 24 h, daytime and night-time pressures were 129/80, 137/88 and 121/72 mmHg, respectively. These boundaries were not materially altered when we considered only the 275 participants who had been normotensive both at home and at the clinic (127/79, 135/87 and 118/72 mmHg, respectively). When, in addition to the Belgian data, other reports on large cohorts were also analysed, the transition from normotension to hypertension on ambulatory measurement was likely to be within the ranges of 130-135/80-85, 135-140/85-90 and 120-125/70-75 mmHg for 24 h, daytime and night-time pressures, respectively. CONCLUSION: In comparison with other population surveys and with the earlier interim reports on the Belgian study, the present analysis produced remarkably consistent results with respect to the distributions of the ambulatory measurements. The working definitions of normality based on the 95th percentiles of the ambulatory measurements in the normotensive participants in the present survey and various other studies need further validation in terms of the incidence of cardiovascular complications. For this purpose, the Belgian participants as well as other cohorts are being prospectively followed.

Advantages and disadvantages of the meta-analysis approach

Abstract: Advantages of meta-analysisLiterature reviews have traditionally been largely narrative. Meta-analysis now offers the opportunity to critically evaluate and statistically combine results of comparable studies or trials. Its major purposes are to increase the numbers of observations and the statistic

Public Health Implications of Environmental Exposure to Cadmium and Lead: An Overview of Epidemiological Studies in Belgium:

Abstract: The CadmiBel Study was a cross-sectional population study that investigated the health effects of environmental exposure to cadmium and lead. The 2327 participants constituted a random sample of the population of four Belgian districts, chosen in order to provide a wide range of environmental exposu

Prognostic Value of Invasive Hemodynamic Measurements at Rest and During Exercise in Hypertensive Men

Abstract: In 1994, we ascertained the outcome of 143 hypertensive men in whom invasive hemodynamic measurements were performed at rest and during graded bicycle exercise during the period 1972-1982 to assess (1) which of the hemodynamic components of blood pressure is associated with the incidence of cardiovascular events and total mortality, and (2) whether the hemodynamic response to dynamic exercise adds prognostic precision to the data at rest. During 2186 patient years of follow-up, 38 patients suffered at least one fatal or nonfatal cardiovascular event and 17 patients died. Cox regression analysis showed that systolic pressure and systemic vascular resistance measured at rest, during submaximal exercise (50 W), and at peak effort were significant ( P P P

Power spectral analysis of RR interval and blood pressure short-term variability at rest and during dynamic exercise : Comparison between cyclists and controls

Abstract: To determine the adaptations of the autonomic nervous system in the control of heart rate and blood pressure induced by endurance training, 10 competitive cyclists aged 27 ± 7 years and 10 age, weight- and height-matched sedentary controls were subjected to Power Spectral Analysis of the RR interval and of blood pressure at supine rest and during submaximal cycloer-gometric exercise test in the supine position at 20 % and 40 % of maximal workload. At rest, the high-frequency (HF) power of the RR interval was higher in cyclists (p < 0.05) compared to) controls, whereas the power spectrum of both systolic and diastolic blood pressure did not differ between cyclists and controls. During exercise the variance, the low-frequency (LF) and the HF power of the RR interval decreased significantly (p < 0.005) and similarly in cyclists and controls. The LF/HF ratio of the RR interval increased (p < 0.001) and the alfa index of baroreflex sensitivity decreased (p < 0.05) without differences between cyclists and controls. The variance of both systolic and diastolic blood pressure increased (p < 0.001 and p < 0.005, respectively) as well as the HF power of systolic blood pressure (p < 0.001) similarly in cyclists and in controls. In conclusion, the data of the present study suggest that competitive cycling causes an enhanced vagal drive to the sinus node, whereas the neural control of blood pressure is not affected. During exercise a vagal withdrawal and a sympathetic activation in the neural control of heart: rate, together with a reduction of baroreflex sensitivity are operative. These changes are similar in cyclists and controls.

Lead Exposure and Conventional and Ambulatory Blood Pressure: A Prospective Population Study

Abstract: Objective. —To evaluate in a prospective fashion the association between low-level lead exposure and blood pressure. Design. —Prospective cohort study. Setting. —General population. Participants. —A random population sample (N=728; 49% men; age range, 20-82 years) was studied in Belgium for 1985 through 1989 and reexamined for 1991 through 1995. Mean Outcome Measures. —At baseline and follow-up, blood pressure was measured by conventional sphygmomanometry (15 total readings) and at followup also by 24-hour ambulatory monitoring. Lead exposure was estimated from blood lead and zinc protoporphyrin concentrations. Multivariate analyses controlled for sex, age, body mass index, smoking and drinking habits, physical activity, exposure at work, social class, menopausal status, use of medications (antihypertensive medication, oral contraceptives, hormonal replacement therapy), hematocrit or hemoglobin, serum total calcium concentration, 24-hour urinary sodium and potassium excretion, and γ-glutamyltransferase activity. Results. —At baseline, mean (SD) systolic/diastolic conventional blood pressure was 130 (17)/77 (9) mm Hg. The mean blood lead concentration was 0.42 μmol/L (8.7 μg/dL), and the mean zinc protoporphyrin concentration was 1.0 μg per gram of hemoglobin. Over the 5.2-year median follow-up, the mean blood lead concentration dropped by 32% (0.14 μmol/L [2.9 μg/dL]) (P Conclusions. —Lead exposure at the intensity studied (

Effect of strength training on blood pressure measured in various conditions in sedentary men.

Abstract: To examine the effect of long term strength training on heart rate and blood pressure, measured in different conditions, and on their variability, thirty healthy, previously sedentary men were randomized into a training and a control group. The strength training program consisted of 48 training sessions on a multigym apparatus at a frequency of 3 sessions each week, involving leg press, bench press, leg curl, shoulder press, leg extension and sit ups. The control group was asked not to change their sedentary lifestyle. In the subjects of the training group the load could be increased significantly for all exercises (p < 0.01). Heart rate and blood pressure were measured at rest in the supine and sitting position, during 24 hours with a non-invasive ambulatory device and during an exercise test on a cycloergometer. Repeated measures analysis of variance did not show an effect of strength training on heart rate or on blood pressure. In addition, power spectral analysis of the RR interval (ECG) and of the beat-to-beat blood pressure in the supine subject revealed similar total, low frequency and high frequency power before and after training, indicating that the neural control of both heart rate and blood pressure was not affected by a 16-week program of strength training.

Long-term blood pressure control in older Chinese patients with isolated systolic hypertension: a progress report on the Syst-China trial

Abstract: This report on the ongoing double-blind placebo-controlled Syst-China trial investigated whether antihypertensive drug treatment based mainly on a calcium entry blocker and a converting enzyme inhibitor, would be suitable for maintaining long-term blood pressure (BP) control in older Chinese patients (average age: 67 years) with isolated systolic hypertension (systolic pressure 160-219 mm Hg and diastolic pressure < 95 mm Hg). Active treatment consisted of nitrendipine (10- 40 mg/day) with the possible addition of captopril (12.5- 50 mg/day) and hydrochlorothiazide (12.5-50 mg/day), as necessary to reduce systolic pressure to a level of 150 mm Hg or lower and by at least 20 mm Hg. Matching placebos were used in the control group. This progress analysis was restricted to BP control up to 3 years of follow-up. The placebo (n = 1134) and active treatment n = 1245) groups had similar characteristics at enrolment. The sitting BP averaged 170/86 mm Hg. Systolic pressure fell (P < 0.001) on average 8 mm Hg more on active treatment than on placebo and diastolic pressure 3 mm Hg more. Fewer patients remained on monotherapy in the placebo than in the active treatment group (P < 0.001); on placebo the second and third line medications were started more frequently (P < 0.001). This progress report showed that significant BP reduction can be achieved and maintained in older Chinese patients treated with a calcium antagonist, associated with a converting-enzyme inhibitor and a thiazide, as necessary. Whether this BP reduction would result in a clinically meaningful decrease of cardiovascular complications is still under investigation.

Associations of orthostatic blood pressure fall in older patients with isolated systolic hypertension

Abstract: Objectives To investigate the associations of the orthostatic blood pressure changes in older patients with isolated systolic hypertension. Methods A total of 2716 patients, 917 men and 1799 women, aged > or = 60 years, were examined at three separate outpatient visits whilst receiving placebo during the single-blind run-in phase of the Syst-Eur trial. The orthostatic blood pressure changes were calculated by subtracting the average of two blood pressure readings with the patient in the supine position from the mean of two readings obtained after the patient had stood for 2 min. An orthostatic blood pressure drop by at least 20 mmHg systolic or 10 mmHg diastolic was considered exaggerated. Results For the three run-in visits combined, the supine blood pressure was 175 +/- 13 mmHg systolic and 86 +/- 6 mmHg diastolic (means +/- SD). With the patients standing the systolic blood pressure was 5 +/- 12 mmHg lower, whereas the diastolic blood pressure was 2 +/- 7 mmHg higher. An exaggerated fall in systolic blood pressure was observed on at least 1 visit in 21.0% of the patients and on all three visits in 2.5%. The corresponding values for diastolic blood pressure were 9.7 and 0.4%. The orthostatic fall in systolic blood pressure increased with previous antihypertensive treatment, age and smoking, but decreased with a higher sitting pulse rate and usual alcohol consumption versus none. The rise in diastolic blood pressure upon standing was higher in women than in men, was curvilinearly associated with age and increased with the sitting diastolic blood pressure. By multiple logistic regression analysis, the odds of having a persistent or occasional exaggerated orthostatic fall in systolic blood pressure were 22% higher in women than in men. The odds increased with previous antihypertensive treatment (by 42%), age (by 1.4%/year), electrocardiographic left ventricular mass (by 15%/mV) and sitting systolic blood pressure (by 0.9%/mmHg), but decreased with sitting pulse rate (by 1.9%/beat per min). An exaggerated orthostatic fall in diastolic blood pressure was 30% more likely in men; the likelihood increased with age (by 6.4%/year) and decreased with sitting diastolic blood pressure (by 6.6%/mmHg). Conclusion An exaggerated orthostatic blood pressure fall in older patients with isolated systolic hypertension is associated mainly with gender, age and blood pressure level. Previous antihypertensive treatment, a lower pulse rate and a lower electrocardiographic left ventricular mass were also associated with an exaggerated orthostatic fall in systolic blood pressure.

Ambulatory monitoring uncorrected for placebo overestimates long-term antihypertensive action

Abstract: This study compares blood pressure (BP) changes during active antihypertensive treatment and placebo as assessed by conventional and ambulatory BP measurement. Older patients (> or = 60 years, n=337) with isolated systolic hypertension by conventional sphygmomanometry at the clinic were randomized to placebo or active treatment consisting of nitrendipine (10 to 40 mg/d), with the possible addition of enalapril (5 to 20 mg/d) and/or hydrochlorothiazide (12.5 to 25 mg/d). At baseline, clinic systolic/diastolic BP averaged 175/86 mm Hg and 24-hour and daytime ambulatory BPs averaged 148/80 and 154/85 mm Hg, respectively. After 13 months (median) of active treatment, clinic BP had dropped by 22.7/7.0 mm Hg and 24-hour and daytime BPs by 10.5/4.5 and 9.7/4.3 mm Hg, respectively (P<.001 for all). However, clinic (9.8/1.6 mm Hg), 24-hour (2.1/1.1 mm Hg), and daytime (2.9/1.0 mm Hg) BPs decreased also during placebo (P<.05, except for daytime diastolic BP); these decreases represented 43%/23%, 20%/24%, and 30%/23% of the corresponding BP fall during active treatment. After subtraction of placebo effects, the net BP reductions during active treatment averaged only 12.9/5.4, 8.3/3.4, and 6.8/3.2 mm Hg for clinic, 24-hour, and daytime BPs, respectively. The effect of active treatment was also subject to diurnal variation (P<.05). Changes during placebo in hourly systolic and diastolic BP means amounted to (median) 21% (range, -1% to 42%) and 25% (-3% to 72%), respectively, of the corresponding changes during active treatment. In conclusion, expressed in millimeters of mercury, the effect of antihypertensive treatment on BP is larger with conventional than with ambulatory measurement. Regardless of whether BP is measured by conventional sphygmomanometry or ambulatory monitoring, a substantial proportion of the long-term BP changes observed during active treatment may be attributed to placebo effects. Thus, ambulatory monitoring uncorrected for placebo or control observations, like conventional sphygmomanometry, overestimates BP responses in clinical trials of long duration.

Antihypertensive therapy in older patients with isolated systolic hypertension: the Syst-Eur experience in general practice

Abstract: Background and objective. This interim report from the Syst-Eur trial investigated the level of blood pressure control achieved during the double-blind period in patients followed in general practices. Methods. In the Syst-Eur trial elderly patients (60 years or older) with isolated systolic hypertension were randomized to either active or placebo treatment. Active treatment consisted of nitrendipine combined with enalapril and/or hydrochlorothiazide to reduce systolic pressure to Results. This analysis was restricted to patients of general practitioners who had been followed for at least 12 months. The placebo (N = 204) and active treatment (N = 217) groups had similar characteristics at randomization. At one year, the difference in sitting pressure between the two treatment groups was 10 mmHg systolic and 4 mmHg diastolic. Fewer patients remained on monotherapy in the placebo than in the active treatment group and on placebo the second and third line medications were started earlier. Nitrendipine tablets were discontinued in 10 patients on placebo and in 21 patients assigned to active treatment (P Conclusions. A significant blood pressure reduction can be achieved and maintained in older patients with isolated systolic hypertension followed by general practitioners. Whether this blood pressure reduction results in a clinically meaningful decrease of cardiovascular complications is under investigation. Keywords. Antihypertensive treatment, general practice, isolated systolic hypertension, randomized clinical trial.

Prognostic significance of peak oxygen uptake in hypertension.

Abstract: The aim of this study was to investigate the prognostic value of cardiopulmonary fitness in hypertension. From 1972 to 1982 oxygen uptake and heart rate were recorded during an exercise test to exhaustion in 216 patients (143 men). Their outcome was ascertained in 1994. During 3,411 patient years of follow-up, 53 patients suffered at least one fatal or nonfatal cardiovascular event and 25 patients died. After adjustment for age, gender, and weight, the relative hazard rates (RHR ; Cox regression) of peak oxygen uptake (l.min -1 ) amounted to 0.44 (P = 0.01) for the first occurring cardiovascular events and 0.35 (P = 0.05) for all-cause mortality. These RHR remained significant after additional adjustment for traditional cardiovascular risk factors (RHR = 0.45 and 0.28, respectively ; P < 0.05). Heart rate at 50 W did not predict outcome after adjustment for age and gender (P = 0.94 and 0.14, respectively), nor after additional adjustment for heart rate at rest (P = 0.86 and 0.61, respectively). In conclusion, a lower peak oxygen uptake, but not a higher submaximal heart rate, is significantly and independently associated with a higher incidence of cardiovascular events and a higher total mortality in hypertensive patients.

Conventional and ambulatory blood pressure measurement in older patients with isolated systolic hypertension:second progress report on the ambulatory blood pressure monitoring project in the Syst-Eur trial.

Abstract: OBJECTIVES: To compare clinic and ambulatory blood pressure measurement and the reproducibility of these measurements in older patients with isolated systolic hypertension.PATIENTS: A total of 477 patients aged >/= 60 years with isolated systolic hypertension on clinic measurement were monitored during the placebo run-in phase of the Syst-Eur trial. METHODS: The time-weighted 24 h blood pressure, clock time day and night blood pressure, the cumulative sum-derived crest and trough blood pressure and the high and low blood pressure levels of the square-wave model were computed. The daily alteration between the high and low blood pressure spans was quantified using the clock time day-night difference, the cumulative sum-derived circadian alteration magnitude, the Fourier amplitude and the difference between the high and low blood pressure levels of the square-wave model. RESULTS: The daytime ambulatory systolic blood pressure was, on average, 21 mmHg lower than the clinic blood pressure, whereasthe diastolic blood pressure was, on average, similar with both techniques of measurement. In the 132 patients who underwent repeat measurements, clinic blood pressure levels and the parameters describing the difference betgween the daily high and low blood pressure spans were equally reproducible. However, both were less reproducible than the ambulatory blood pressure levels. The repeatability coefficients, expressed as percentages of near maximum variation, were 50 and 51% for the clinic systolic and diastolic blood pressures, 30 and 33% for the mean 24 h systolic and diastolic blood pressures and between 44 and 54% for the parameters describing the daily alteration between the high and low blood pressure spans. CONCLUSION: In older patients with isolated systolic hypertension, clinic and ambulatory systolic blood pressure may differ greatly; the prognostic significance of this difference remains to be elucidated. Furthermore, the level of blood pressure in these patients is more reproducible by ambulatory measurement than it is by clinic measurement.

Ambulatory Blood Pressure Monitoring in Clinical Trials

Abstract: Ambulatory blood pressure monitoring is increasingly used in clinical trials. The preliminary threshold values proposed for diagnosing hypertension and adjusting treatment based on ambulatory monitoring cannot yet be widely recommended because they have not been validated in prospective studies. The trough-to-peak or surface ratios may be useful instruments for assessing the duration of action of antihypertensive drugs. Trials with ambulatory monitoring just as clinical experiments based on conventional sphygmomanometry need to be properly controlled, because ambulatory blood pressure measurement is not completely devoid of a placebo effect. Ambulatory compared with conventional blood pressure measurements are characterized by higher reproducibility which makes it possible to reduce sample size in cross-over but not in parallel group trials. Finally, ambulatory monitors used in clinical research should have successfully passed one of the standardized validation protocols.

Life style as a blood pressure determinant.

Abstract: In Belgium, an affluent Western European country, participation in sports, alcohol intake, and living in a working class area were identified as the life style factors with the closest associations with the blood pressure level. Obesity was another important blood pressure correlate. Sodium intake, determined from the 24 h urinary output, and smoking were not associated with blood pressure. Controlled intervention studies have proven that weight reduction, endurance training and alcohol abstinence effectively reduce blood pressure. In the light of these intervention studies, the Belgian findings and the published work highlight the potential of preventive strategies aimed at these major life style factors.

Reversal of left ventricular hypertrophy.

Abstract: To the Editor. —In their meta-analysis on the reversal of left ventricular hypertrophy in essential hypertension, Dr Schmieder and colleagues 1 identified 471 references that reported results on regression of left ventricular mass with antihypertensive drugs. They then applied strict selection criteria and only the results of 39 clinical trials with a doubleblind, randomized, controlled, parallel-group design were retained. The authors are to be congratulated for the important and meticulous work they have done. However, I was somewhat surprised by the subsequent statistical analysis of the data. Whereas the individual studies were designed as comparative studies, the authors used each treatment arm of these selected trials as a separate observation and, therefore, gave up the major advantage of the original design. In my view, a more appropriate analysis would have been not only to calculate the changes within each treatment arm, but also to analyze the differences between the changes

Treatment of hypertensive patients according to the conventional or ambulatory pressure: a progress report on the APTH trial. APTH Investigators. Ambulatory Blood Pressure and Treatment of Hypertension.

Abstract: The main objective of the Ambulatory Blood Pressure and Treatment of Hypertension (APTH) trial is to test the hypothesis that antihypertensive treatment based on ambulatory monitoring may be more beneficial than treatment guided by conventional sphygmomanometry. After a 2-month run-in period on single-blind placebo, hypertensive patients were randomized to two groups, one in which the target pressure was a sitting diastolic pressure from 80 through 89 mm Hg on conventional sphygmomanometry (conventional blood pressure [CBP] group), and one in which a daytime (from 10 to 20 h) diastolic pressure from 80 through 89 mm Hg had to be achieved (ambulatory blood pressure [ABP] group). After randomization all patients were started on lisinopril 10 mg/day. One month later lisinopril could be continued at 10 or 20 mg/day or discontinued depending on the attained blood pressure level. This article is an interim report on 207 patients followed for two months into the trial. At one month lisinopril was discontinued more frequently in the ABP than the CBP group (24 vs 9 patients, p = 0.004). Nevertheless at two months, blood pressure control was not significantly different in the two treatment groups. The baseline-adjusted differences in systolic pressure between the two treatment arms of the trial (ABP-CBP group) were +2.7 mm Hg (95% confidence interval [CI]): -2.9, +8.3) for the conventional pressure, +0.4 mm Hg (CI: -4.3, +5.1) for the 24 h pressure, -0.1 mm Hg (CI: -5.1, +4.8) for the daytime pressure and -0.7 mm Hg (CI: -6.7, +5.4) for the night-time pressure. The corresponding differences in diastolic pressure were -1.3 mm Hg (CI: -4, +1.4), +0.1 mm Hg (CI: -3, +3.1), -1.1 mmgH (CI: -4.4, +2.1) and +0.3 mm Hg (CI: -3.7, +4.3), respectively. Thus, the present findings do not refute the APTH research hypothesis. In terms of blood pressure control and the number of patients remaining on antihypertensive drugs, treatment based on ambulatory recordings may be preferable to treatment guided by conventional sphygmomanometry.

Hypertension and lead exposure.

Abstract: To the Editor. —The suggestion by Dr Hu and colleagues 1 that long-term lead accumulation, as reflected by the tibia bone lead level, may be an independent risk factor for developing hypertension in men should be cautiously interpreted. Of the subjects classified as hypertensive, 44% had a blood pressure higher than 160 mm Hg systolic, 95 mm Hg diastolic, or both. 1 These thresholds are 1 mm Hg more than the published World Health Organization (WHO)/International Society of Hypertension (ISH) limits, which Dr Kim and colleagues applied in a second article in the same issue ofTHE JOURNAL. 2 Reclassifying individuals may impact on the association size and its significance. The analyses treating blood pressure as a continuous variable and avoiding the problem of having to define arbitrary cutoff points will be reported elsewhere, but a reference was not provided. According to WHO/ISH guidelines, the diagnosis of hypertension requires that pressure is measured

Ambulatory blood pressure monitoring in clinical trials.

Abstract: Ambulatory blood pressure monitoring is increasingly being used in clinical trials. Trials with ambulatory monitoring, just like clinical experiments based on conventional sphygmomanometry, need to be controlled properly, because ambulatory blood pressure measurements are not completely devoid of placebo-like effects. The trough: peak ratio might be a useful instrument for assessment of the durations of action of antihypertensive drugs. However, its error term and confidence interval need to be reported and its determination in clinical trials requires further standardization. Ambulatory compared with conventional blood pressure measurements are characterized by a higher reproducibility. This property makes a reduction in sample size possible in cross-over but not in parallel group trials, if instead of the conventional blood pressure the 24 h or daytime blood pressures are compared. Trials focusing on the full course of the blood pressure through the day need a larger sample size than do those just concerning the conventional blood pressure level.