Circadian Urinary Excretion of Water, and Not Salt, Is Affected by the White Coat Effect

Hypertension is an important morbidity factor. The prognostic consequences of the white-coat effect have been studied extensively. The repercussion on the circadian rhythm of urinary water and salt excretion in the same subgroup remain, conversely, among the open topics. Postulating an impaired diurnal sodium and volume excretion we decided to investigate both, in subjects with or without a white-coat effect, in the general population. A sample of 1023 subjects, has been considered. We collected 24-h urine samples, divided in day and night, and we measured the blood pressure with an Ambulatory Blood Pressure Monitoring (ABPM). ABPM values were then compared with physician collected in-office values to assign subjects to the group with or without the white-coat effect. Concerning the circadian pattern of urinary sodium excretion, we found no significant differences between the groups. There was instead in the white-coat effect group a higher night/day ratio of urinary water excretion. The white-coat effect, has been considered a potential hypertension precursor, and its consequent handling could be prospectively relevant in hypertension prevention. The absence of repercussions on the urinary circadian sodium excretion pattern and on the potentially related risk factors in subjects with a white coat effect is reassuring. The clinical significance of the impact on the night/day ratio of water excretion needs to be further investigated.

Nocturnal blood pressure rather than night-to-day blood pressure ratio is related to arterial stiffening in untreated young and middle-aged adults with non-dipper hypertension

Little is known about nocturnal blood pressure (BP) or night-to-day BP ratio, which is a more specific determinant of arterial stiffness in subjects with non-dipper hypertension? This study aims to investigate the correlation of nocturnal BP and brachial-ankle pulse wave velocity (ba PWV), an index of arterial stiffness in untreated young and middle-aged adults with non-dipper hypertension. A cross-sectional analysis of baseline parameters of the NARRAS trial was performed. Twenty-four hour ambulatory BP measurements, ba PWV and routine clinical data collection were performed in all patients. The relationship of 24-h ambulatory BP profiles, biochemical measures as well as demographic parameters and ba PWV were analyzed using Pearson's correlation and multiple stepwise regression analysis. A total of 77 patients (mean age 47.0 ± 11.7 years) with non-dipper hypertension were included. Age, height, weight and nocturnal systolic BP were related to ba PWV in Pearson's correlation analysis. In stepwise regression analysis, age (β = 10.57, 95% confidence interval (CI): 6.099-15.042, p < 0.001) and weight (β = -3.835, 95% CI: -7.658--0.013, p = 0.049) are related to ba PWV. Nocturnal systolic BP (β = 8.662, 95% CI: 2.511-14.814, p = 0.006) was the independent predictors of ba PWV, even after night-to-day systolic BP ratio or 24-h ambulatory BP profile were taken into account. Nocturnal systolic BP rather than night-to-day systolic BP ratio appears to be a more specific determinant for arterial stiffness, as assessed by ba PWV in young and middle-aged adults with non-dipper hypertension. 24-h ambulatory BP measurements are essential for cardiovascular risk evaluation.

Extreme altitude changes between night and day during marathon flights of great snipes

Several factors affect the flight altitude of migratory birds, such as topography, ambient temperature, wind conditions, air humidity, predation avoidance, landmark orientation, and avoiding over-heating from direct sunlight.^1-6 Recent tracking of migratory birds over long distances has shown that migrants change flight altitude more commonly and dramatically than previously thought.^4-8 The reasons behind these altitude changes are not well understood. In their seasonal migrations between Sweden and sub-Saharan Africa, great snipes Gallinago media make non-stop flights of 4,000-7,000 km, lasting 60-90 h.^9,10 Activity and air pressure data from multisensor dataloggers showed that great snipes repeatedly changed altitudes around dawn and dusk, between average cruising heights about 2,000 m (above sea level) at night and around 4,000 m during daytime. Frequency and autocorrelation analyses corroborated a conspicuous diel cycle in flight altitude. Most birds regularly flew at 6,000 m and one bird reached 8,700 m, possibly the highest altitude ever recorded for an identified migrating bird. The diel altitude changes took place independently of climate zone, topography, and habitat overflown. Ambient temperature, wind condition, and humidity have no important diel variation at the high altitudes chosen by great snipes. Instead, improved view for orientation by landmarks, predator avoidance, and not least, seeking cold altitudes at day to counteract heating from direct sunlight are the most plausible explanations for the diel altitude cycle. Together with similar recent findings for a small songbird,⁶ the great snipes' altitudinal performance sheds new light on the complexity and challenges of migratory flights.

Relationship between arterial stiffness and circadian pattern of blood pressure

Arterial stiffness is a risk factor for cardiovascular morbidity and mortality. The relationship between the arterial stiffness and the circadian pattern of blood pressure (BP) has been controversial. The objective of the present study was to investigate the relationship between arterial stiffness by pulse wave analysis (PWA) and variables of 24-hour ambulatory BP monitoring (ABPM) in patients with high normal BP or hypertension (HTN).Five hundred forty-eight patients (304 males, 48 ± 12-year-old) with high normal BP or HTN were enrolled. BP was measured at the outpatient clinic and 24-hour ABPM was performed. Using radial applanation tonometry, PWA was performed for evaluation of systemic arterial stiffness. Patients were classified into four groups according to the dipping patterns: a nocturnal dipping group, an isolated systolic non-dipping group, an isolated diastolic non-dipping group and a both systolic and diastolic non-dipping group. For adjustment of age, population was divided to 2 groups: old group ≥55 year-old (n = 158, 75 males), young group <55 year-old (n = 390, 229 males).According to the dipping patterns, augmentation pressure (AP), augmentation index (AI) and heart rate (75 bpm) adjusted AI (AI@HR75) showed statistically significant difference (P = .011, .009, and .018, respectively). Multivariate analysis showed that isolated diastolic non-dipping was correlated with arterial stiffness expressed as AI and AI@HR 75, only in young group (β-coefficient = 12.6, P = .04 and β-coefficient = 7.503, P = .028, respectively).Arterial stiffness might be closely related with the pattern of non-dipping in young patients with HTN and high normal BP.

Breast-Milk Cortisol and Cortisone Concentrations Follow the Diurnal Rhythm of Maternal Hypothalamus-Pituitary-Adrenal Axis Activity

BACKGROUND

Very preterm infants often receive donor milk from mothers who deliver at term, but its composition differs from that of their own mother's milk. Because breast-milk glucocorticoids can support developing neonates, we explored concentration variability within and between mothers.

OBJECTIVE

We hypothesized that breast-milk glucocorticoid concentrations would be higher after very preterm delivery [gestational age (GA) <32 wk; study 1] and would follow the diurnal rhythm of maternal adrenocortical activity (study 2).

METHODS

Study 1 assessed differences in milk cortisol, cortisone, and the cortisone-to-(cortisol+cortisone) ratio of mothers who delivered at (median) GA: 28.6 wk or at term weekly during the first month postpartum. Study 2 assessed variations in milk cortisol, cortisone, and the cortisone-to-(cortisol+cortisone) ratio over 24 h, and tested Pearson correlations between milk and salivary concentrations in mothers who delivered at term (median GA: 38.9 wk) during week 4 postpartum. In these studies, foremilk glucocorticoids were measured by liquid chromatography-tandem mass spectrometry. Associations of milk cortisol, milk cortisone, and the milk cortisone-to-(cortisol+cortisone) ratio with prematurity (study 1) or collection time (study 2) were studied with longitudinal data analyses.

RESULTS

In study 1, giving birth to a very preterm infant was associated with reductions in milk cortisol and cortisone concentrations of 50% (β: 0.50; 95% CI: 0.26, 0.99; P = 0.05) and 53% (β: 0.53; 95% CI: 0.30, 0.93; P = 0.03), respectively, when adjusted for collection time. In study 2, concentrations of milk cortisol and cortisone were associated with collection time (both P < 0.01), peaking at ∼0700. Milk and salivary concentrations of cortisol (r = 0.92, P < 0.01) and cortisone (r = 0.93, P < 0.01) as well as the cortisone-to-(cortisol+cortisone) ratio (r = 0.64, P < 0.01) were correlated with one another.

CONCLUSIONS

Breast-milk glucocorticoid concentrations follow the diurnal rhythm of maternal hypothalamus-pituitary-adrenal axis activity and are lower in mothers who deliver very preterm.

Validating faecal glucocorticoid metabolite analysis in the Virunga mountain gorilla using a natural biological stressor

The continued degradation of primate habitat worldwide is forcing many primate populations into small protected forest islands surrounded by high-density human populations. One well-studied example is the critically endangered mountain gorilla (Gorilla beringei beringei). Decades of monitoring and research on Rwanda's mountain gorillas offer a unique opportunity to use non-invasive endocrine analysis to address pressing questions about the conservation of this endangered population. The aims of our study were as follows: (i) to validate field and laboratory methods for assessing stress through faecal glucocorticoid metabolite (FGM) analysis using inter-social unit interactions as a natural stressor; (ii) to determine the excretion lag times between interactions and detectable stress response in faeces; and (iii) to determine whether there are circadian patterns of FGM excretion. We collected ~6000 faecal samples from 127 known gorillas in 10 habituated groups, monitored by the Dian Fossey Gorilla Fund's Karisoke Research Center over 21 months in 2011 and 2012. Extracted FGMs were measured using a cortisol enzyme immunoassay (R4866; C. J. Munro). Results revealed cause-effect relationships between inter-unit interactions and increased FGMs (relative to individual pre-event samples) between 20 and 140 h after interactions, with the peak most often occurring on day 3. There was no evidence of circadian patterns in FGM concentrations, as previously shown in many species with long gut passage times. However, baseline FGM concentrations were lower in adult males than in adult females, and variation was associated with the collection month, indicating possible seasonal variation. This study provides a biologically validated, field-friendly faecal hormone metabolite extraction and laboratory enzyme immunoassay analysis method for non-invasive monitoring of adrenocortical activity in Virunga mountain gorillas. The methods are useful for future evaluation of a variety of environmental and human-induced potential stressors in this critically endangered population.

Office and ambulatory blood pressure control in hypertensive patients treated with different two-drug and three-drug combinations

There is scarce information regarding ambulatory blood pressure (BP) achieved in daily practice with a wide range of antihypertensive drug combinations. We looked for differences in office and ambulatory BP among major drug combinations of two and three antihypertensive agents from a different drugs class. A total of 17187 patients treated with six types of two-drug combinations and 9724 treated with six types of three-drug combinations from the Spanish ABPM Registry were analyzed. We compared achieved office and ambulatory BP, as well as office (< 140/90 mmHg) and ambulatory (24-hour BP < 130/80; day BP < 135/85, and night BP < 120/70 mmHg) BP control among groups. The combination of renin-angiotensin system (RAS) blockers with diuretics and the triple combination of RAS blockers with diuretics and calcium channel blockers (CCB) were associated with lower values of 24-hour, daytime and nighttime BP, as well as more pronounced nocturnal BP dip. Compared with such combinations (reference), other double combinations had lower rates of ambulatory BP control. Moreover, triple combinations containing alpha blockers also had lower rates of ambulatory BP control. We conclude that even with similar office BP control, differences exist among antihypertensive two-drug and three-drug combinations with respect to ambulatory BP control achieved during treatment, with RAS blockers/diuretics and RAS blockers/CCBs/diuretics obtaining better control rates. This can help physicians choose among drug combinations in order to obtain further ambulatory BP reductions.

Circadian fluctuations in three types of sensory modules in healthy subjects

This study was designed to observe and compare the circadian fluctuations in tactile sense, joint reposition sense and two-point discrimination in healthy subjects. Twenty-one healthy adult subjects received perceptual ability tests through these three different sensory modules at approximately 9:00, 13:00 and 18:00 in a day. The distribution of ranking for perceptual ability was significantly different among the three different time points in each individual, with highest perceptual ability in the evening compared with noon and morning, in terms of tactile sense and two-point discrimination. These findings suggest that the perceptual ability of healthy subjects fluctuates according to the time points in a day.

Nocturnal hypertension or nondipping: which is better associated with the cardiovascular risk profile?

BACKGROUND

Both increased night blood pressure (BP) and nondipping are associated with worse cardiovascular risk and prognosis. However, as they are often related features, their relative importance has been difficult to assess separately. In this study we address separate associations of nocturnal hypertension and nondipping with cardiovascular risk profile in treated and untreated hypertensive patients.

METHODS

A total of 37,096 untreated patients and 62,788 patients receiving antihypertensive treatment from the Spanish Ambulatory Blood Pressure Monitoring Registry were included. Each cohort was separated into 4 groups: group 1, night systolic blood pressure (SBP) <120 mm Hg and normal dipping (>10%); group 2, night SBP <120 mm Hg and nondipping (≤10%); group 3, nocturnal hypertension (SBP ≥120 mm Hg) and normal dipping; and group 4, nocturnal hypertension and nondipping.

RESULTS

The smallest proportion of patients with additional cardiovascular risk factors, organ damage, and history of previous events was observed in the group with both normal night SBP and dipping, whereas those with both nocturnal hypertension and nondipping showed the largest proportion of cardiovascular risk factors and diseases. When groups showing only 1 abnormality were compared, nondipping was associated with female sex, reduced renal function, and previous cardiovascular events, whereas nocturnal hypertension was associated with male sex, smoking, and increased urinary albumin excretion. In treated patients, it was also associated with the presence of diabetes.

CONCLUSION

Nondipping is related to more advanced disease (reduced renal function and clinical evidence of cardiovascular disease), whereas nocturnal hypertension is associated with albuminuria. The worst cardiovascular risk profile is present in patients exhibiting both nocturnal hypertension and nondipping.

Circadian pattern of intraocular pressure fluctuations in young myopic eyes with open-angle glaucoma

PURPOSE

To characterize the circadian pattern of habitual-position intraocular pressure (IOP) and its association with ocular dimension in young myopic patients with open-angle glaucoma (OAG).

METHODS

A total of 108 young OAG patients with moderate to severe myopia (myopia group) and 67 age-matched OAG patients with emmetropia or mild myopia (control group) were recruited prospectively over 3 years. IOP was recorded 11 times over a 24-hour period by a single, well-trained ophthalmology resident using a handheld tonometer.

RESULTS

A total of 87 men and 88 women were included in this study. Analysis of the entire myopia group indicated no acrophase in habitual-position IOP over 24 hours. Subgroup analysis indicated that 44 patients (40.7%) had a diurnal acrophase, 17 patients (15.7%) had a nocturnal acrophase, and 47 patients (43.6%) had no evident acrophase. By contrast, the control group showed an overall nocturnal acrophase in habitual-position IOP, with 14 patients (20.8%) having a diurnal acrophase, 30 patients (44.8%) having a nocturnal acrophase, and 23 patients (34.4%) having no evident acrophase in subgroup analysis. There was a negative correlation between nocturnal habitual-position IOP elevation and axial length in the overall population.

CONCLUSIONS

In young myopic OAG eyes, there is no significant nocturnal elevation in habitual-position IOP, while IOP increases at night-time in age-matched control eyes. The overall 24-hour IOP pattern in the myopia group did not show an acrophase. Finally, data showed a negative relationship between nocturnal habitual-position IOP elevation and axial length.

Chronopharmacology of anti-convulsive therapy

Approximately one-third of patients with epilepsy continue to have seizures despite antiepileptic therapy. Many seizures occur in diurnal, sleep/wake, circadian, or even monthly patterns. The relationship between biomarkers and state changes is still being investigated, but early results suggest that some of these patterns may be related to endogenous circadian patterns whereas others may be related to wakefulness and sleep or both. Chronotherapy, the application of treatment at times of greatest seizure susceptibility, is a technique that may optimize seizure control in selected patients. It may be used in the form of differential dosing, as preparations designed to deliver sustained or pulsatile drug delivery or in the form of 'zeitgebers' that shift endogenous rhythms. Early trials in epilepsy suggest that chronopharmacology may provide improved seizure control compared with conventional treatment in some patients. The present article reviews chronopharmacology in the treatment of epilepsy as well as future treatment avenues.

Diffusion-weighted imaging-fluid attenuated inversion recovery mismatch in nocturnal stroke patients with unknown time of onset

BACKGROUND

More than a quarter of patients with ischemic stroke (IS) are excluded from thrombolysis because of an unknown time of symptom onset. Recent evidence suggests that a mismatch between diffusion-weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR) imaging could be used as a surrogate for the time of stroke onset. We compared used the DWI-FLAIR mismatch and the FLAIR/DWI ratio to estimate the time of onset in a group of patients with nocturnal strokes and unknown time of onset.

METHODS

We used a prospectively collected acute IS patient database with MRI as the initial imaging modality. Nineteen selected nocturnal stroke patients with unknown time of onset were compared with 22 patients who had an MRI scan within 6 hours from stroke onset (control A) and 19 patients who had an MRI scan between 6 and 12 hours (control B). DWI and FLAIR signal was rated as normal or abnormal. FLAIR/DWI ratio was calculated from independent DWI and FLAIR ischemic lesion volumes using semiautomatic software.

RESULTS

The DWI-FLAIR mismatch was different among groups (unknown 43.7%; control A 63.6%; control B 10.5%; Fisher-Freeman-Halton test; P = .001). There were significant differences in FLAIR/DWI ratio among the 3 groups (unknown 0.05 ± 0.12; control A 0.17 ± 0.15; control B 0.04 ± 0.06; Kruskal-Wallis test; P < .0001). Post-hoc pairwise comparisons revealed that FLAIR/DWI ratio from the unknown group was significantly different from the control B group (P = .0045) but not different from the control A group. DWI volumes were not different among the 3 groups.

CONCLUSIONS

A large proportion of patients with nocturnal IS and an unknown time of stroke initiation have a DWI-FLAIR mismatch, suggesting a recent onset of stroke.

Temporal variation of out-of-hospital cardiac arrests in an equatorial climate

OBJECTIVE

We aimed to determine whether there is a seasonal variation of out-of-hospital cardiac arrests (OHCA) in an equatorial climate, which does not experience seasonal environmental change.

METHODS

We conducted an observational prospective study looking at the occurrence of OHCA in Singapore. Included were all patients with OHCA presented to Emergency Departments across the country. We examined the monthly, daily, and hourly number of cases over a three-year period. Data was analyzed using analysis of variance (ANOVA).

RESULTS

From October, 1st 2001 to October, 14th 2004, 2428 patients were enrolled in the study. Mean age for cardiac arrests was 60.6 years with 68.0% male. Ethnic distribution was 69.5% Chinese, 15.0% Malay, 11.0% Indian, and 4.4% Others. There was no significant seasonal variation (spring/summer/fall/winter) of events (ANOVA P = 0.71), monthly variation (P = 0.88) or yearly variation (P = 0.26). We did find weekly peaks on Mondays and a circadian pattern with daily peaks from 9-10 am.

CONCLUSIONS

We did not find any discernable seasonal pattern of cardiac arrests. This contrasts with findings from temperate countries and suggests a climatic influence on cardiac arrest occurrence. We also found that sudden cardiac arrests follow a circadian pattern.

Evidence from knockout mice for distinct implications of neuropeptide-Y Y2 and Y4 receptors in the circadian control of locomotion, exploration, water and food intake

Members of the neuropeptide-Y (NPY) family acting via Y2 and/or Y4 receptors have been proposed to participate in the control of ingestive behaviour and energy homeostasis. Since these processes vary between day and night, we explored the circadian patterns of locomotor, exploratory and ingestive behaviour in mice with disrupted genes for Y2 (Y2-/-) or Y4 (Y4-/-) receptors. To this end, the LabMaster system was used and its utility for the analysis of changes in circadian activity and ingestion caused by gene knockout evaluated. Female animals, aged 27weeks on average, were housed singly in cages fitted with sensors for water and food intake and two infrared frames for recording ambulation and rearing under a 12h light/dark cycle for 4days. Relative to WT animals, diurnal locomotion, exploration, drinking and feeding were reduced, whereas nocturnal locomotion was enhanced in Y2-/- mice. In contrast, Y4-/- mice moved more but ate and drank less during the photophase, while they ate more and explored less during the scotophase. Both Y2-/- and Y4-/- mice weighed more than WT mice. These findings attest to a differential role of Y2 and Y4 receptor signalling in the circadian control of behaviours that balance energy intake and energy expenditure. These phenotypic traits can be sensitively and continuously recorded by the LabMaster system.