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

Impact of Blood Pressure Variability on Cardiovascular Events in Elderly Patients with Hypertension

Blood pressure variability is one of the characteristic features of hypertension in the elderly. However, its clinical significance remains to be determined. We therefore examined the impact of blood pressure variability on the development of cardiovascular events in elderly hypertensive patients. A total of 106 consecutive hypertensive patients aged more than 60 years old (mean age, 73.9 +/- 8.1 years old; male, 54%), all of whom underwent 24-h ambulatory blood pressure monitoring, were followed up (median, 34 months; range, 3-60 months). During the follow-up period, 39 cardiovascular events were observed, including 14 cases of cerebral infarction and 7 cases of acute myocardial infarction. The coefficient of variation (CV) of 24-h systolic blood pressure (SBP) values was used as an index of blood pressure variability. The patients showed a mean CV value of 10.6%, and were divided into two groups according to this mean value as a cut-off point: a high CV group (n = 46) and a low CV group (n = 60). Although baseline clinical characteristics were similar in the two groups, Kaplan-Meier plots for event-free survival revealed that the rate of cardiovascular events was significantly higher in high CV group than in low CV group (p < 0.05). Cox's proportional hazards analysis showed that increased blood pressure variability (a high CV value of 24-h SBP) was an independent predictive variable for cardiovascular events. The CV value of daytime SBP and the SD value of both 24-h SBP and daytime SBP also had positive correlations with the onset of cardiovascular events. These results suggest that increased blood pressure variability may be an independent risk factor for cardiovascular events in elderly hypertensive patients.

Blunted reduction in night-time blood pressure is associated with cognitive deterioration in subjects with long-standing hypertension

OBJECTIVE

Data about the relationship of blunted reduction of night-time blood pressure (BP) with cognitive deterioration (CD) are conflicting. This study aims to explore this possible association in elderly people with long-standing hypertension.

METHODS

Twenty-six hypertensive subjects consecutively admitted to a rehabilitation unit over a six-month period were recruited. Exclusion criteria concerned all clinical conditions potentially related to BP variability or leading to CD. All patients underwent a clinic and 24-h BP non-invasive monitoring assessment of BP, as well as a cognitive assessment with the Mini Mental State Examination (MMSE). The presence of cerebrovascular disease (CVD) was assessed on CT films, with a standardized visual rating scale.

RESULTS

Blunted reduction of both systolic and diastolic night-time BP were significantly associated with poorer cognitive performances (r=0.61, p=0.001 for systolic; and r=0.57, p=0.002 for diastolic, respectively). In a multiple regression model, blunted reduction of night-time BP (B=0.17, [95% confidence intervals: 1.1-1.3], p=0.008 for systolic; and B=0.15, [95% confidence intervals: 1.0-1.3], p=0.02 for diastolic) independently predicted poorer cognitive performances.

CONCLUSIONS

In subjects with long-standing hypertension the blunted reduction of night-time BP is independently associated with lower cognitive performances.

Greater Change of Orthostatic Blood Pressure Is Related to Silent Cerebral Infarct and Cardiac Overload in Hypertensive Subjects

Greater change of postural blood pressure (BP) is often seen in elderly hypertensives and is recognized as a risk factor for cognitive decline and poorer cerebrovascular outcome, but its clinical significance still remains to be clarified. We performed a head-up tilting test, ambulatory BP monitoring, and brain MRI in 59 hypertensives and 27 normotensive subjects. We measured plasma atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels at rest to assess cardiac burden. The 59 hypertensive patients were classified into 3 groups: an orthostatic hypertension (OHT) group with orthostatic increase in systolic BP (SBP) > or = 10 mmHg (n=16); an orthostatic hypotension (OHYPO) group with orthostatic SBP decrease < or = -10 mmHg (n=18); and an orthostatic normotension (ONT) group with neither of these two patterns (n=25). A group of 27 normotensive subjects (NT) was also included as a control. Plasma BNP (72 +/- 92 vs. 29 +/- 24 pg/ml, p < 0.05) and BNP/ANP ratio (4.6 +/- 3.3 vs. 2.4 +/- 1.5, p < 0.05) were significantly higher in the OHYPO than in the NT group. The BNP/ANP ratio was also higher in the OHT than in the NT group (5.1 +/- 3.9 vs. 2.4 +/- 1.5, p < 0.01). The number of silent cerebral infarct (SCI), prevalence of SCI and number of multiple SCIs was the highest in the OHT group, followed in order by the OHYPO, ONT and NT groups. Blood pressure and left ventricular mass index were not significantly different among the 3 hypertensive groups. In conclusion, hypertensive patients with greater change of postural BP (OHT and OHYPO) were shown to have increased risk of advanced silent brain lesions and greater cardiac burden.

Event-Related Brain Potentials in Elderly Dippers and Nondippers with Recently Diagnosed Hypertension

Several studies have shown a relationship between blood pressure (BP) and cognitive function. Yet very few studies have addressed circadian BP patterns in this context, perhaps due to poor availability of suitable methods to detect slight changes in the cognitive state. Today, brain event-related potentials (ERPs) allow us to detect subclinical changes in cognitive function. We enrolled 30 elderly patients with recently diagnosed hypertension (<2 years) that had never been treated: 18 dippers and 12 nondippers. Patients underwent 24-h ambulatory blood pressure monitoring (ABPM). Careful assessment of their cognitive state was carried out using the mini mental state examination (MMSE), and the recording of P300 and N2 ERPs. No significant differences between the two groups were found. MMSE scores in dippers and nondippers were similar (29.5+/-0.71 vs. 29.3+/-1.07, respectively; p =0.611), as were P300 latency values (377.78+/-33.28 vs. 364.67+/-35.12 in the central (Cz) position, p =0.310; 379.22+/-32.94 vs. 365.25+/-35.07 in the occipital (Pz) position, p =0.277) and N2 wave latency values (253.83+/-24.9 vs. 249.17+/-24.47 in the Cz position, p =0.617; 251.56+/-25.86 vs. 246.58+/-25.46 in the Pz position, p =0.608). These data show no association between the nondipping pattern and lower cognitive function in elderly subjects with recent hypertension.

Reduced Endothelial Vasomotor Function and Enhanced Neointimal Formation after Vascular Injury in a Rat Model of Blood Pressure Lability

Increased short-term blood pressure variability is known to be associated with hypertensive target organ damage. Sinoaortic denervation (SAD) induces a marked increase in blood pressure lability without affecting the average blood pressure level. The aim of this study was to investigate the effects of blood pressure lability on endothelial vasomotor function and neointimal formation after balloon injury in SAD rats. Direct longterm measurement of mean arterial pressure showed no significant difference in the average of mean arterial pressure between the SAD group and sham-operated control group. In contrast, the standard deviation of mean arterial pressure, as an index of blood pressure lability, was 3-fold greater in SAD rats. To study endothelial function, isometric tension of aortic rings was measured 4 weeks after SAD or sham operation. Endothelium-dependent vasorelaxation induced by acetylcholine was significantly reduced in the SAD group (20% reduction at maximum relaxation). Endothelium-independent vasorelaxation induced by sodium nitroprusside was similar in each group. Acetylcholine-induced NO release from aortic rings was significantly reduced in the SAD group. Next, we examined neointimal formation in carotid arteries in SAD and sham-operated rats at 2 weeks after balloon injury. The neointimal-to-medial area ratio in the SAD group was 50% higher than that in the sham-operated group. The percentage of proliferating cell nuclear antigen-positive cells in the intima was significantly higher in the SAD group. These findings suggest that increased blood pressure lability, independently of average blood pressure level, impairs endothelial function by inhibiting NO production, enhances neointimal formation after balloon injury, and may thereby contribute to atherogenesis.

Pulsating renal blood flow distribution measured using power Doppler ultrasound: correlation with hypertension

Arterial compliance is associated with the first stage of hypertension and atherosclerosis. We propose here a compliance index, which measures pulsating renal blood flow distribution using a power Doppler ultrasound (US). We assessed the relationship between the compliance index and blood pressure and between the compliance index and risk factors of atherosclerosis. The subjects consisted of 136 consecutive patients (96 males, 40 females) who underwent a physical checkup. Ages ranged from 40 to 60 years with a mean of 50.1 years. Patients with past renal disease and/or renal dysfunction were excluded. Using a power Doppler US combined with an ECG-gated and echo-tracking system, we recorded the vascular distribution of the renal parenchyma at 8 to 10 time points during an interval of the R wave of the ECG. Using a color pixel counting technique, we calculated the area (A) corresponding to the colored vascular distribution at power Doppler US. The relationships between A and the time points (t) were fitted to a quadratic equation. The compliance index of renal parenchymal vessels was obtained by twice differentiating the quadratic equation obtained above (d2A/dt2), and taking the result as a new hemodynamic index. In the univariate correlation analysis, the compliance index was correlated with age (r=-0.26, p=0.002), systolic blood pressure (r=-0.33, p=0.0001), diastolic blood pressure (r=-0.45, p<0.0001), serum uric acid (r=-0.28, p=0.001), and body mass index (r=-0.32, p=0.0002). On the multivariate stepwise regression analysis, the compliance index was significantly correlated with diastolic blood pressure (beta=-0.36, p<0.0001) and body mass index (beta=-0.18, p<0.0001). In conclusion, the compliance index is a candidate for a new hemodynamic marker of renal blood flow abnormality caused by hypertension.

The relationship between changes in normal-range systolic blood pressure and cognitive function in middle-aged healthy women

Little is known about the effect of normal-range blood pressure (BP) on cognitive function. In previous studies investigating the relationship between BP and cognitive function in elderly subjects, underlying cerebrovascular damage has complicated the interpretation of results. To reveal the relationship between BP levels that were within an absolutely normal range and cognitive function, we examined cognitive function in normotensive, healthy middle-aged women. BP levels were measured on three separate occasions at 1-month intervals, and the subjects exhibiting normotension (< 140/90 mmHg) throughout the evaluation period were recruited as normotensive subjects. Cognitive function was assessed using subtests of the Wechsler Adult Intelligence Scale-Revised. The study demonstrated that, among the subtests examined, the scores on the Digit Symbol Test, an index of psychomotor performance, had a significant correlation with normotensive-range systolic blood pressure (SBP) (r=-0.51, p<0.05); this relation was negative-that is, higher but still normal-range SBP levels were associated with impaired Digit Symbol Test scores. In addition, the relationship adjusted by age and educational level was also significant (partial correlation = -0.56, p<0.05). In contrast, diastolic BP was not related to the Digit Symbol Test (r = -0.33, p = 0.13). Furthermore, the Digit Symbol Test was not influenced by blood glucose or serum cholesterol levels. These findings suggested that, even within the normotensive range, lower levels of SBP might be protective against impairment of psychomotor speed in middle-aged women.

Clinical significance of blood pressure response triggered by a doctor's visit in patients with essential hypertension

The clinical significance of the pressor response triggered by blood pressure measurement, the so-called "white-coat effect," was studied in relation to left ventricular structure and function in patients with essential hypertension. We studied 75 consecutive, never-before treated patients with essential hypertension (54 +/- 2 (SE) years; 31 men). Beat-to-beat blood pressure (Finapres) was monitored at rest, during conventional blood pressure measurement by a doctor, and during a mental stress test. The left ventricular mass index and diastolic function (EIA ratio) were determined by echocardiography. The systolic blood pressure response triggered by the doctor's visit (deltaSBP) correlated positively with the left ventricular mass index (r= 0.326, p<0.03) and negatively with the EIA ratio (r=-0.325, p<0.02). A positive relationship between the deltaSBP and left ventricular mass index was observed in men (r=0.556, p<0.01) but not in women. The greater ASBP also was associated with lower EIA ratio in women (r=-0.434, p<0.02). The deltaSBP correlated with the mental stress-induced increase in systolic blood pressure in men (r=0.586, p<0.005) but not in women (r=0.148, n.s.). Blood pressures outside the clinic were higher in men than in women (p<0.05 for systolic and p<0.005 for diastolic) despite the similar level of clinic blood pressures between the sexes. Stepwise multiple linear regression analysis showed that the deltaSBP was an independent predictor of the left ventricular mass index in men (beta=0.783, p=0.0009) and of the EIA ratio in women (beta=-0.003, p=0.05). These data suggest that the pressor response triggered by a doctor's visit has clinical significance in never-before treated hypertensive patients, possibly because it mirrors real-life stress reactivity in men.

Altered diurnal variation of blood pressure in elderly subjects with decreased activity of daily living and impaired cognitive function

Activity of daily living (ADL) and cognitive are indices of physical and psychological activity in elderly subjects. The present study was performed to clarify the relationship among ADL, cognitive function, and ambulatory blood pressure (ABP) in the elderly. Study subjects were 77 females and 22 males (aged 60 to 101 years) with various levels of ADL and cognition, who were in nursing homes or geriatric hospitals. ABP was recorded every 30 min for 24 h by a noninvasive device. Mini-mental state examination (MMSE) and Barthel index measurement were used to evaluate cognitive function and ADL, respectively. Both the MMSE and Barthel index values showed a significant positive correlation with daytime ABP but not with nighttime ABP. The dip in nighttime BP correlated negatively with age, and positively with MMSE and Barthel index. In the multiple regression analysis, age and Barthel index values remained significant determinants of the dip in nighttime BP. Presence of stroke and MMSE became significant when the Barthel index values were removed from the analyses. When subjects were classified by tertiles of MMSE or Barthel index, subjects in the lowest MMSE group and those in the lowest Barthel index group had both lower daytime ABP and smaller nighttime BP dip than those of the other groups. A low BP level during the daytime was associated with altered diurnal variation of BP in elderly subjects with greater age, impaired cognitive function, and/or decreased ADL. ADL had a greater influence on diurnal BP variation than did cognitive function.