The structural and functional consequences of diurnal variations in blood pressure in treated patients with hypertensive cerebrovascular disease

Nocturnal blood pressure dipping, blood pressure variability, and cognitive function in early and middle-aged adults

Higher nighttime blood pressure (BP), less BP dipping, and higher BP variability have been linked with worse cognitive function in the elderly. The goal of this study is to explore whether this relationship already exists in early and middle adulthood. We further examined whether ethnic differences between African Americans and European Americans in BP parameters can explain ethnic differences in cognitive function. 24-h ambulatory BP monitoring and cognitive function were obtained from 390 participants (average age: 37.2 years with a range of 25-50; 54.9% African Americans; 63.6% females). We observed that higher nighttime BP, decreased dipping, and higher variability were significantly associated with lower scores on the Picture Sequence Memory Test. Significant negative associations between variability and overall composite scores were also observed. No significant associations between average 24-h or daytime BP and cognitive function were observed. Ethnic differences in nighttime diastolic pressures and dipping can explain 6.81% to 10.8% of the ethnicity difference in the score of the Picture Sequence Memory Test (ps < .05). This study suggests that the associations of nighttime BP, dipping, and variability with cognitive function already exist in young and middle-aged adults. Ethnic differences in nighttime BP and dipping can at least partially explain ethnic differences in cognitive function. The stronger association of these parameters with cognitive function than daytime or average BP in this age range raises the importance of using ambulatory BP monitoring for more precise detection of abnormal BP patterns in young adulthood.

Twenty-four hour blood pressure variability and the prevalence and the progression of cerebral white matter hyperintensities

Blood pressure variability (BPV) is related to cerebral white matter hyperintensities (WMH), but longitudinal studies assessing WMH progression are scarce. Patients with cardiovascular disease and control participants of the Heart-Brain Connection Study underwent 24-hour ambulatory blood pressure monitoring and repeated brain MRI at baseline and after 2 years. Using linear regression, we determined whether different measures of BPV (standard deviation, coefficient of variation, average real variability (ARV), variability independent of the mean) and nocturnal dipping were associated with WMH and whether this association was mediated or moderated by baseline cerebral perfusion. Among 177 participants (mean age: 65.9 ± 8.1 years, 33.9% female), the absence of diastolic nocturnal dipping was associated with higher WMH volume at baseline (β = 0.208, 95%CI: 0.025-0.392), but not with WMH progression among 91 participants with follow-up imaging. None of the BPV measures were associated with baseline WMH. Only 24-hour diastolic ARV was significantly associated with WMH progression (β = 0.144, 95%CI: 0.030-0.258), most profound in participants with low cerebral perfusion at baseline (p-interaction = 0.042). In conclusion, absent diastolic nocturnal dipping and 24-hour diastolic ARV were associated with higher WMH volume. Whilst requiring replication, these findings suggest that blood pressure patterns and variability may be a target for prevention of small vessel disease.

Associations of Nocturnal Blood Pressure With Cognition by Self-Identified Race in Middle-Aged and Older Adults: The GENOA (Genetic Epidemiology Network of Arteriopathy) Study

BACKGROUND

Whether the association of blood pressure (BP) during sleep (nocturnal BP) with cognition differs by race is unknown.

METHODS AND RESULTS

Participants in the GENOA (Genetic Epidemiology Network of Arteriopathy) Study underwent ambulatory BP measurements, brain magnetic resonance imaging, and cognitive function testing (the Rey Auditory Verbal Learning Test, the Digit Symbol Substitution Task, and the Trail Making Test Part B) between 2000 and 2007. We examined multivariable linear regression models of the nocturnal BP-cognition association. Among 755 participants (mean age, 63 years; 64% women; 42% self-identified black race; 76% taking antihypertensive medication), mean nocturnal systolic BP (SBP)/diastolic BP was 126/69 mm Hg, daytime SBP/diastolic BP level was 139/82 mm Hg, and mean reduction in SBP from day to night (dipping) was 9%. Among the entire sample, a race interaction was observed in Digit Symbol Substitution Task and Trail Making Test Part B (both P<0.15). Race-stratified analyses showed that a 1-SD increase in nocturnal SBP levels was associated with poorer Digit Symbol Substitution Task and log-transformed Trail Making Test Part B scores (unstandardized regression coefficient [95% confidence interval]: -1.98 [-3.28 to -0.69] and 0.06 [0.004-0.12]; both P<0.05) in black but not white individuals. Additional adjustments for white matter hyperintensity volumes or brain atrophy, measured via brain magnetic resonance imaging, did not change the results. Results were similar when nocturnal SBP dipping was assessed as the exposure, yet daytime SBP levels yielded no association with cognition.

CONCLUSIONS

Nocturnal SBP measurements may be useful in assessing the potential risk for lower cognitive function in middle-aged and older adults, particularly in black individuals.

Nocturnal Blood Pressure in Young Adults and Cognitive Function in Midlife: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

Nocturnal blood pressure (BP) is associated with risk for cardiovascular events. However, the relationship between nocturnal BP in young adults and cognitive function in midlife remains unclear.

METHODS

We used data from the ambulatory BP monitoring substudy of the Coronary Artery Risk Development in Young Adults Study, including 224 participants (mean age 30 years, 45% men, 63% African Americans). At the 20-year follow-up, the Stroop test (executive function), Digit Symbol Substitution Test (psychomotor speed), and Rey Auditory Verbal Learning Test (verbal memory) were assessed.

RESULTS

Baseline mean office, daytime, and nocturnal BP were 109/73, 120/74, and 107/59 mm Hg, respectively. Nocturnal BP dipping, calculated as (nocturnal systolic BP [SBP]--daytime SBP) × 100/daytime SBP, was divided into quartiles (Q1: -39.3% to -16.9%; Q2: -16.8% to -13.2%, Q3 [reference]: -13.1% to -7.8%, and Q4: -7.7% to +56.4%). In multiple regression analyses, the least nocturnal SBP dipping (Q4 vs. reference) and higher nocturnal diastolic BP level were associated with worse Stroop scores, with adjustments for demographic and clinical characteristics, and cumulative exposure to office BP during follow-up (β [standard error]: 0.37 [0.18] and 0.19 [0.07], respectively; all P < 0.05). Digit Symbol Substitution Test and Rey Auditory Verbal Learning Test were not significantly associated with nocturnal SBP dipping or nocturnal SBP/diastolic BP levels.

CONCLUSIONS

Among healthy young adults, less nocturnal SBP dipping and higher nocturnal diastolic BP levels were associated with lower executive function in midlife, independent of multiple measures of office BP during long-term follow-up.

Impact of nocturnal heart rate variability on cerebral small-vessel disease progression: a longitudinal study in community-dwelling elderly Japanese

Recent evidence has shown an effect of ambulatory heart rate (HR) on cardiovascular events and mortality. Our objective was to determine whether ambulatory HR was related to the progression of cerebral small-vessel disease (SVD) or cognitive decline in community-dwelling elderly people. A cohort of 190 community-dwelling elderly people underwent an ambulatory blood pressure monitoring (ABPM), brain magnetic resonance imaging (MRI) and cognitive testing at baseline, with MRI and cognitive tests repeated 4 years later. HR variability in ABPM was quantified by the s.d. (s.d. and the root mean square of successive differences (RMSSD), and the relationship between HR variability and the progression of SVD/cognitive decline was investigated. We also assessed the association of nighttime HR variability and nocturnal HR dipping. The nighttime RMSSD of participants with the progression of SVD was significantly higher than that of those without progression of SVD (P<0.05). Moreover, nighttime RMSSD was independently associated with the progression of SVD (1 b.p.m. increment: odds ratio=1.13, 95% confidence interval=1.04-1.24, P<0.01). We failed to confirm an association between cognitive decline and nighttime HR variability. However, s.d. in the daytime and 24-h HR were independently related to cognitive decline (P<0.05). Nocturnal HR dipping was least in the top quartiles of nighttime HR variability, with a monotonic trend of nocturnal HR dipping that was dependent on the quartiles of nighttime HR variability indices (P<0.01). Increased HR variability during the night is a predictor of the progression of SVD in community-dwelling elderly people.

Ambulatory blood pressure in stroke and cognitive dysfunction

We have reviewed the most relevant data regarding ABPM and brain damage, with specific reference to first and recurrent stroke, silent structural brain lesions such as lacunar infarcts and white matter lesions, and cognitive impairment. Only two large studies have evaluated the usefulness of ABPM in relation to antihypertensive treatment in primary stroke prevention. In the Syst-Eur trial, drug treatment reduced ABPM and office BP more than placebo in patients with sustained isolated systolic hypertension (ISH). In contrast, in those patients with white-coat hypertension (WCH) changes in ABPM between the treatment groups were not significantly different. Patients with WCH had a lower incidence of stroke (p < 0.05) during follow-up than patients with sustained ISH, suggesting that WCH is a benign condition. In the HYVET trial 50 % of the very elderly patients included with office systolic BP > 160 mmHg had WCH. However, a significant 30 % stroke reduction was observed in treated patients including those with WCH, indicating that WCH may not be a benign condition in the elderly. In the acute stroke setting, where treatment of hypertension is not routinely recommended due to the lack of evidence and the differing results of the very few available trials, ABPM data shows that sustained high BP during the first 24 h after acute stroke is related to the formation of cerebral edema and a poorer functional status. On the other hand, even when nondipping status was initially related to a poorer prognosis, data indicate that patients with very-large nocturnal dipping, the so-called "extreme dippers", are those with the worse outcomes after stroke. The association between different ABPM parameters (circadian pattern, short-term variability) and poorer performance scores in cognitive function tests have been reported, especially in elderly hypertensives. Unfortunately most of these studies were cross-sectional and the associations do not establish causality.

Associations between Ambulatory Blood Pressure Parameters and Cerebral White Matter Lesions

Silent cerebral white matter lesions (WMLs) are a common finding on magnetic resonance imaging of the brain in the elderly. However, in patients with hypertension, WMLs tend to occur earlier in life and appear to be more severe. There is a body of evidence that supports the idea that WMLs in asymptomatic hypertensive patients should be considered a silent early marker of brain damage. It is known that ambulatory blood pressure monitoring (ABPM) correlates more closely with hypertension-related organ damage than office blood pressure. This paper focuses on the associations between blood pressure parameters obtained by 24-hour ABMP and cerebral WMLs.

Nocturnal blood pressure in untreated essential hypertensives

AIM. Prevalence, correlates and reproducibility of nocturnal hypertension (NH) as defined by fixed cut-off limits in uncomplicated essential hypertension are poorly defined. Therefore, we assessed such issue in a cohort of 658 untreated hypertensives. METHODS. All subjects underwent procedures including cardiac and carotid ultrasonography, 24-h urine collection for microalbuminuria, ambulatory blood pressure monitoring (ABPM), over two 24-h periods within 4 weeks. NH was defined according to current guidelines (i.e. night-time blood pressure, BP ? 120/70 mmHg) and non-dipping status as a reduction in average systolic (SBP) and diastolic BP (DBP) at night lower than 10% compared with daytime values. RESULTS. A total of 477 subjects showed NH during the first and second ABPM period; 62 subjects had normal nocturnal BP (NN) in both ABPM sessions. Finally, 119 subjects changed their pattern from one ABPM session to the other. Overall, 72.5% of subjects had reproducible NH, 18% variable pattern (VP) and 9.5% reproducible NN. In the same group, figures of reproducible non-dipping, variable dipping and reproducible dipping pattern were 24%, 24% and 52%, respectively. Among NH patients, 56% of whom were dippers, subclinical cardiac organ damage was more pronounced than in their NN counterparts. CONCLUSIONS. In uncomplicated essential hypertensives, NH is a more frequent pattern than non-dipping; NH is associated with organ damage, independently of dipping/non-dipping status. This suggests that options aimed at restoring a blunted nocturnal BP fall may be insufficient to prevent cardiovascular complications unless night-time BP values are fully normalized.