Acute effect of coffee drinking on dynamic cerebral autoregulation

Cardiovascular and cerebrovascular effects of caffeine maintenance in preterm infants during the transitional period

BACKGROUND AND AIM

Caffeine is routinely used for the prophylaxis of prematurity-related apnoeas. We aimed to evaluate the effect of caffeine maintenance on cardiovascular and cerebrovascular haemodynamics using a non-invasive multimodal monitoring in preterm infants during the transitional period.

METHODS

Infants <32 weeks' gestational age (GA) were enrolled in this observational prospective study. The following parameters were recorded before and after the administration of caffeine citrate 5 mg/kg using near-infrared spectroscopy, pulse oximetry and electrical velocimetry: heart rate, cardiac output, stroke volume, cardiac contractility, systemic vascular resistance (SVR), perfusion index, peripheral and cerebral oxygenation, cerebral fractional oxygen extraction, correlation index between cerebral oxygenation and heart rate (TOHRx, marker of cerebrovascular reactivity). Multilevel mixed-effects linear models were used to assess the impact of caffeine and of relevant clinical covariates on each parameter.

RESULTS

Seventy-seven infants (mean GA 29.3 ± 2.5 weeks, mean birthweight 1148 ± 353 g) were included. Caffeine administration was associated with increased SVR (B = 0.623, p = 0.004) and more negative TOHRx values (B = -0.036, p = 0.022), which suggest improved cerebrovascular reactivity.

CONCLUSIONS

Caffeine administration at maintenance dosage during postnatal transition is associated with increased systemic vascular tone and improved cerebrovascular reactivity. A possible role for caffeine-mediated inhibition of adenosine receptors may be hypothesized.

IMPACT

This study provides a thorough and comprehensive overview of multiple cerebrovascular and cardiovascular parameters, monitored non-invasively by combining near-infrared spectroscopy, electrical velocimetry and pulse oximetry, before and after the administration of caffeine at maintenance dosage in preterm infants during postnatal transition. Caffeine was associated with an improvement in cerebrovascular reactivity and with a slight but significant increase in systemic vascular resistance, with no additional effects on other cardiovascular and cerebrovascular parameters. Our results support the safety of caffeine treatment even during a phase at risk for haemodynamic instability such as postnatal transition and suggest potential beneficial effects on cerebral haemodynamics.

Acute Effects of Coffee Consumption on Blood Pressure and Endothelial Function in Individuals with Hypertension on Antihypertensive Drug Treatment: A Randomized Crossover Trial

INTRODUCTION

Coffee is a complex brew that contains several bioactive compounds and some of them can influence blood pressure (BP) and endothelial function (EF), such as caffeine and chlorogenic acids (CGAs).

AIM

This study aimed to evaluate the acute effects of coffee on BP and EF in individuals with hypertension on drug treatment who were habitual coffee consumers.

METHODS

This randomized crossover trial assigned 16 adults with hypertension to receive three test beverages one week apart: caffeinated coffee (CC; 135 mg caffeine, 61 mg CGAs), decaffeinated coffee (DC; 5 mg caffeine, 68 mg CGAs), and water. BP was continuously evaluated from 15 min before to 90 min after test beverages by digital photoplethysmography. Reactive hyperemia index (RHI) assessed by peripheral arterial tonometry evaluated EF before and at 90 min after test beverages. At the same time points, microvascular reactivity was assessed by laser speckle contrast imaging. Repeated-measures-ANOVA evaluated the effect of time, the effect of beverage, and the interaction between time and beverage (treatment effect).

RESULTS

Although the intake of CC produced a significant increase in BP and a significant decrease in RHI, these changes were also observed after the intake of DC and were not significantly different from the modifications observed after the consumption of DC and water. Microvascular reactivity did not present significant changes after the 3 beverages.

CONCLUSION

CC in comparison with DC and water neither promoted an acute increase in BP nor produced an improvement or deleterious effect on EF in individuals with hypertension on drug treatment who were coffee consumers.

Cerebral vascular function following the acute consumption of caffeinated artificially- and sugar sweetened soft drinks in healthy adults

Chronic consumption of sugar- and artificially-sweetened beverages (SSB and ASB) are associated with an increased risk of stroke but it is unclear how acute consumption influences cerebral vascular function. Purpose: We hypothesized that: (1) acute consumption of SSB and ASB would augment dynamic cerebral autoregulation (dCA) and attenuate cerebral vascular reactivity to hypercapnia (CVR_CO2) compared to water; and (2) dCA and CVR_CO2 would be attenuated with SSB compared to ASB and water. Methods: Twelve healthy adults (age: 23 ± 2 years, four females) completed three randomized trials where they drank 500 ml of water, SSB (Mountain Dew^®), or ASB (Diet Mountain Dew^®). We measured mean arterial pressure (MAP), middle and posterior cerebral artery blood velocities (MCAv and PCAv), and end-tidal CO₂ tension (PETCO₂). Cerebral vascular conductance was calculated as cerebral artery blood velocity/MAP (MCAc and PCAc). Twenty min after consumption, participants completed a 5 min baseline, and in a counterbalanced order, a CVR_CO2 test (3%, 5%, and 7% CO₂ in 3 min stages) and a dCA test (squat-stand tests at 0.10 Hz and 0.05 Hz for 5 min each) separated by 10 min. CVR_CO2 was calculated as the slope of the linear regression lines of MCAv and PCAv vs. PETCO₂. dCA was assessed in the MCA using transfer function analysis. Coherence, gain, and phase were determined in the low frequency (LF; 0.07-0.2 Hz) and very low frequency (VLF; 0.02-0.07 Hz). Results: MCAv and MCAc were lower after SSB (54.11 ± 12.28 cm/s, 0.58 ± 0.15 cm/s/mmHg) and ASB (51.07 ± 9.35 cm/s, 0.52 ± 1.0 cm/s/mmHg) vs. water (62.73 ± 12.96 cm/s, 0.67 ± 0.11 cm/s/mmHg; all P < 0.035), respectively. PCAc was also lower with the ASB compared to water (P = 0.007). MCA CVR_CO2 was lower following ASB (1.55 ± 0.38 cm/s/mmHg) vs. water (2.00 ± 0.57 cm/s/mmHg; P = 0.011) but not after SSB (1.90 ± 0.67 cm/s/mmHg; P = 0.593). PCA CVR_CO2 did not differ between beverages (P > 0.853). There were no differences between beverages for coherence (P ≥ 0.295), gain (P ≥ 0.058), or phase (P ≥ 0.084) for either frequency. Discussion: Acute consumption of caffeinated SSB and ASB resulted in lower intracranial artery blood velocity and conductance but had a minimal effect on cerebral vascular function as only MCA CVR_CO2 was altered with the ASB compared to water.

The effect of water temperature on orthostatic tolerance: a randomised crossover trial

Purpose

Bolus water drinking, at room temperature, has been shown to improve orthostatic tolerance (OT), probably via sympathetic activation; however, it is not clear whether the temperature of the water bolus modifies the effect on OT or the cardiovascular responses to orthostatic stress. The aim of this study was to assess whether differing water temperature of the water bolus would alter time to presyncope and/or cardiovascular parameters during incremental orthostatic stress.

Methods

Fourteen participants underwent three head-up tilt (HUT) tests with graded lower body negative pressure (LBNP) continued until presyncope. Fifteen minutes prior to each HUT, participants drank a 500 mL bolus of water which was randomised, in single-blind crossover fashion, to either room temperature water (20 °C) (ROOM), ice-cold water (0–3 °C) (COLD) or warm water (45 °C) (WARM). Cardiovascular parameters were monitored continuously.

Results

There was no significant difference in OT in the COLD (33 ± 3 min; p = 0.3321) and WARM (32 ± 3 min; p = 0.6764) conditions in comparison to the ROOM condition (31 ± 3 min). During the HUT tests, heart rate and cardiac output were significantly reduced (p < 0.0073), with significantly increased systolic blood pressure, stroke volume, cerebral blood flow velocity and total peripheral resistance (p < 0.0054), in the COLD compared to ROOM conditions.

Conclusions

In healthy controls, bolus cold water drinking results in favourable orthostatic cardiovascular responses during HUT/LBNP without significantly altering OT. Using a cold water bolus may result in additional benefits in patients with orthostatic intolerance above those conferred by bolus water at room temperature (by ameliorating orthostatic tachycardia and enhancing vascular resistance responses). Further research in patients with orthostatic intolerance is warranted.

Dietary nitrate reduces blood pressure and cerebral artery velocity fluctuations and improves cerebral autoregulation in transient ischemic attack patients

We found dietary nitrate supplementation reduced blood pressure and brain blood flow fluctuations and improved the relationship between blood pressure and brain blood flow in transient ischemic attack patients. Meanwhile, dietary nitrate had no effects on the brain blood vessels’ response to CO2. We attribute the improved brain blood flow stability to the improved myogenic control of blood pressure with dietary nitrate. Our findings indicate that dietary nitrate could be an effective strategy for stabilizing blood pressure and brain blood flow following transient ischemic attack.

Caffeine Delays Retinal Neurovascular Coupling during Dark to Light Adaptation in Healthy Eyes Revealed by Optical Coherence Tomography Angiography

Purpose

The purpose of this study was to investigate the acute effects of caffeine on retinal hemodynamics during dark to light adaptation using optical coherence tomography angiography (OCTA).

Methods

Thirteen healthy individuals (13 eyes) underwent OCTA imaging after dark adaptation and at repeated intervals during the transition to ambient light in two imaging sessions: control and after ingesting 200 mg of caffeine. We analyzed the parafoveal vessel density (VD) and adjusted flow index (AFI) of the superficial capillary plexus (SCP), middle capillary plexus (MCP), and deep capillary plexus (DCP), as well as the vessel length density (VLD) of the SCP. After adjusting for age, refractive error, and scan quality, we compared parameters between control and caffeine conditions.

Results

In the dark, MCP VD decreased significantly after caffeine (−2.63 ± 1.28%). During the transition to light, initially, DCP VD increased (12.55 ± 2.52%), whereas SCP VD decreased (−2.09 ± 0.91%) significantly with caffeine compared to control. By 15 minutes in light, DCP VD reversed and was significantly decreased (−5.45 ± 2.62%), whereas MCP VD increased (4.65 ± 1.74%). There were no differences in AFI or VLD.

Conclusions

We show that, overall, caffeine causes a trend of delayed vascular response in all three macular capillary plexuses in response to ambient light. Whereas the MCP is constricted in the dark, during the transition from dark to light, there is initially delay followed by prolonged constriction of the DCP and constriction followed by slow dilation of the SCP. We posit that these delayed vascular responses may present potential risk of capillary ischemia.

ACUTE EFFECT OF CAFFEINE ON MACULAR MICROCIRCULATION IN HEALTHY SUBJECTS: An Optical Coherence Tomography Angiography Study

PURPOSE

To evaluate the acute effects of caffeine on macular microvasculature using quantitative optical coherence tomography angiography analysis.

METHODS

Fifty-two healthy subjects aged 24 to 48 years were randomly divided into 2 groups: a control group, which received placebo, and a study group, which was subjected to caffeine. All participants underwent optical coherence tomography angiography at baseline and 1 hour after 200-mg oral caffeine intake in the study group and after oral placebo in the control group. Macular flow area, macular vessel density, and foveal avascular zone (FAZ) area were analyzed in both the groups.

RESULTS

The study group consisted of 14 men and 12 women with a mean age of 40.6 ± 8.9 years. The mean age of control group was 39.5 ± 9.4 years, which consisted of 13 men and 13 women. Baseline macular flow area, vessel density, and FAZ area measurements of the study and control groups showed no significant difference (P > 0.05). Oral caffeine intake caused a significant reduction in macular flow area (superficial, deep, and choriocapillaris) and vessel density (P < 0.05). However, there was no statistically significant difference in FAZ area after caffeine intake when compared with baseline measurements (P = 0.063).

CONCLUSION

We found a significant decrease in macular flow area (superficial, deep, and choriocapillaris) and vessel density after caffeine intake. Our findings are consistent with previous studies using other techniques. We believe that the results of this preliminary study will be useful in future studies about this topic.

Chemosensory Sensitivity after Coffee Consumption Is Not Static: Short-Term Effects on Gustatory and Olfactory Sensitivity

Chemosensory sensitivity has great variation between individuals. This variation complicates the chemosensory diagnostics, as well as the creation of a meal with universally high hedonic value. To ensure accurate characterization of chemosensory function, a common rule of thumb is to avoid food/beverages one hour before chemosensory testing. However, the scientific foundation of this time of fast remains unclear. Furthermore, the role of coffee on immediate chemosensitivity is not known and may have implications for optimization of gastronomy and hedonia. The aim of this study is to investigate the modularity effects of coffee consumption on immediate gustatory and olfactory sensitivity. We included 155 participants. By applying tests for olfactory and gustatory sensitivity before and after coffee intake, we found no changes in olfactory sensitivity, but significantly altered sensitivity for some basic tastants. We repeated our experimental paradigm using decaffeinated coffee and found similar results. Our results demonstrate that coffee (regular and decaffeinated) alters the subsequent perception of taste, specifically by increasing the sensitivity to sweet and decreasing the sensitivity to bitter. Our findings provide the first evidence of how coffee impacts short-term taste sensitivity and consequently the way we sense and perceive food following coffee intake-an important insight in the context of gastronomy, as well as in chemosensory testing procedures.

Does Improved Attention Induced by Caffeine Intake Affect Olfactory Function?

Objectives

Past several studies have proven that caffeine facilitates attentional enhancement by acting as an adenosine antagonist once it is absorbed by the body, resulting in improved psycho-behavioral function. Modern clinical olfactory function tests are usually assessed by psychophysical tests but due to a paucity of data, the influence of enhanced attention by caffeine on olfactory function still remains unclear. The objective of this study was to compare results of cognitive function (attention) and olfactory function before and after caffeine administration in order to analyze effects of caffeine on olfactory function in normosmic subjects.

Methods

This study enrolled 49 participants of Konkuk University Hospital with a mean age of 27.7 years who had patent olfactory clefts and no olfactory dysfunction from May 2015 to February 2016. Subjects were restrained from caffeine 10 hours before the test. On day 1, participant’s subjective olfactory function was evaluated before and after uptake of either caffeinated or decaffeinated coffee using visual analog scale (VAS) score, minimum cross-sectional area (MCA) measured by acoustic rhinometry, and the Korean version of Sniffin’ Stick II (KVSS II). Evaluation of participant’s attentional degree was measured by d2 test. On day 2, the same procedure was carried out with counterpart substance. The type of coffee initially administrated was randomly selected.

Results

After administration, caffeinated coffee resulted in significant attentional enhancement than decaffeinated coffee. Results of d2 test showed statistically significant differences in the parameters of total number of errors and omission errors. In both the caffeinated and decaffeinated groups, the patients showed slight increase in VAS score and nasal cavity area; however, the difference was not statistically significant. Also, caffeinated coffee intake compared to decaffeinated coffee intake showed no significant relevance to olfactory function.

Conclusion

Caffeine may significantly improve attentional congnitive function, while not have acute effects on olfactory function.

The effect of caffeine loading on cerebral autoregulation in preterm infants

AIM

To evaluate cerebral autoregulation changes in preterm infants receiving a loading dose of caffeine base.

METHODS

In a cohort of 30 preterm infants, we extracted measures of cerebral autoregulation using time and frequency domain techniques to determine the correlation between mean arterial pressure (MAP) and tissue oxygenation index (TOI) signals. These measures included the cerebral oximetry index (COx), cross-correlation and coherence measures, and were extracted prior to caffeine loading and in the 2 hours following administration of 10 mg/kg caffeine base.

RESULTS

We observed acute reductions in time domain correlation measures, including the cerebral oximetry index (linear mixed model coefficient -0.093, standard error 0.04; p = 0.028) and the detrended cross-correlation coefficient (ρ₅ coefficient -0.13, standard error 0.055; p = 0.025). These reductions suggested an acute improvement in cerebral autoregulation. Features from detrended cross-correlation analysis also showed greater discriminative value than other methods in identifying changes prior to and following caffeine administration.

CONCLUSION

We observed a reduced correlation between MAP and TOI from near-infrared spectroscopy following caffeine administration. These findings suggest an acute enhanced capacity for cerebral autoregulation following a loading dose of caffeine in preterm infants, contributing to our understanding of the physiological impact of caffeine therapy.

Caffeine and the eye

Caffeine, a popular psychostimulant that acts as an adenosine receptor antagonist, is the most widely used drug in history, consumed daily by people worldwide. Knowledge of the physiological and pathological effects of caffeine is crucial in improving public health because of its widespread use. We provide a summary of the current evidence on the effect of caffeine on the eye. Most of the research conducted to date is in relation to cataract and glaucoma, two of the most common eye diseases among the elderly.

Acute impact of drinking coffee on the cerebral and systemic vasculature

Previous studies have suggested that the risk of ischemic stroke increases immediately after drinking coffee. Indeed, drinking coffee, that is, caffeine, acutely increases arterial stiffness as well as blood pressure and peripheral vascular resistance. On the other hand, it has been reported that arterial stiffening is associated with elevation in the pulsatility index (PI) of cerebral blood flow (CBF), which increases the risk of brain disease. However, the effect of drinking coffee on the PI of the CBF and its interaction with arterial stiffness remain unknown. Against this background, we hypothesized that an acute increase in arterial stiffness induced by drinking coffee augments cerebral pulsatile stress. To test this hypothesis, in 10 healthy young men we examined the effects of drinking coffee on the PI of middle cerebral artery blood velocity (MCAv) and brachial‐ankle pulse wave velocity (baPWV) as indices of cerebral pulsatile stress and arterial stiffness, respectively. Mean arterial blood pressure and baPWV were higher (P < 0.01 and P = 0.02), whereas mean MCA_V and mean cerebrovascular conductance index were lower upon drinking coffee (P = 0.02 and P < 0.01) compared with a placebo (decaffeinated coffee). However, there was no difference in the PI of MCAv between drinking coffee and the placebo condition. These findings suggest that drinking coffee does not increase cerebral pulsatile stress acutely despite an elevation in arterial stiffness in the systemic circulation.

A review of caffeine use as a risk or protective factor for women's health and pregnancy

PURPOSE OF REVIEW

To provide a narrative synthesis of recently published studies on caffeine use as a risk or protective factor for health outcomes, with a focus on women's health and pregnancy.

RECENT FINDINGS

Based on predominantly observational studies, moderate caffeine intake has been shown to be a protective factor for liver cancer, certain bowel conditions, colorectal cancer, skin cancer, and regular menstrual cycle function. However, heavy consumption is a risk factor for osteoporosis, urinary incontinence, and poorer birth and child developmental outcomes. Residual confounding and issues surrounding retrospective self-reported intake are cited as key limitations in the majority of these studies. Moderate caffeine intake has been associated with lower risk of cardiovascular disease and metabolic syndrome; however, recent genetic epidemiology studies provide no evidence for a causal relationship.

SUMMARY

Greater inclusion of female participants in studies, and analysis of sex differences in the relationship between caffeine intake and certain health conditions, is necessary. The current literature suggests caffeine's role as a risk or protective factor differs across health conditions. Often, there are plausible biological mechanisms for this relationship. However, a continued precautionary stance is recommended until direct causal pathways are established. Review of recently published studies does not suggest that current intake guidelines for adults and for pregnant woman need to be modified.