Posts tagged blood pressure
Articles and news from the latest research reports.
Researchers Identify New Pathway Linking the Brain to High Blood Pressure
New research by scientists at the University of Maryland School of Medicine (UM SOM) and the Ottawa Heart Institute has uncovered a new pathway by which the brain uses an unusual steroid to control blood pressure. The study, which also suggests new approaches for treating high blood pressure and heart failure, appears today in the journal Public Library of Science (PLOS) One.
“This research gives us an entirely new way of understanding how the brain and the cardiovascular system work together,” said Dr. John Hamlyn, professor of physiology at the University of Maryland School of Medicine, one of the principal authors. “It opens a new and exciting way for us to work on innovative treatment approaches that could one day help patients.”
For decades, researchers have known that the brain controls the diameter of the peripheral arteries via the nervous system. Electrical impulses from the brain travel to the arteries via a network of nerves known as the sympathetic nervous system. This system is essential for daily life, but is often chronically overactive in high blood pressure and heart failure. In fact, many drugs that help with hypertension and heart failure work by decreasing both acute and chronic activity in the sympathetic nervous system. However, these drugs often have serious side effects, such as fatigue, dizziness and erectile dysfunction. “These drawbacks have led to the search for novel ways to inhibit the sympathetic nervous system while causing fewer problems for hypertension and heart failure patients,” says Dr. Frans Leenen, director of hypertension at the Ottawa Heart Institute, and a principal author of the study.
Working with an animal model of hypertension, Dr. Hamlyn and Dr. Mordecai Blaustein, professor of physiology and medicine at the UM SOM, and their research partner, Dr. Leenen, found a new link between the brain and increased blood pressure, namely, a little-known steroid called ouabain (pronounced WAH-bane). Ouabain was discovered in human blood more than 20 years ago by Dr. Hamlyn and Dr. Blaustein, along with scientists at the Upjohn Company. The new study is the first to identify the particular pathway that connects the brain to ouabain’s effects on proteins that regulate arterial calcium and contraction. Through this mechanism, ouabain makes arteries more sensitive to sympathetic stimulation, and as a result the enhanced artery constriction promotes chronic hypertension.
“Now that we understand the role of ouabain, we can begin working on how to modify this new pathway to help people with cardiovascular problems,” said Dr. Blaustein. “The potential for this is big.” Dr. Blaustein, who has been doing research on the substance since 1977, said medications that block ouabain’s effects might improve the lives of people with hypertension and heart failure.
The researchers, who include Vera Golovina, Ph.D., an adjunct associate professor of physiology at UM SOM, and Bing Huang, M.D, Ph.D., a research associate at the Ottawa Heart Institute, also found significant new evidence that ouabain is manufactured by mammals, a question that had not been previously answered.
“This discovery underscores the crucial importance of basic research here at the School of Medicine,” said Dean E. Albert Reece, MD, PhD, MBA, as well as vice president of medical affairs, the University of Maryland and the John Z. and Akiko Bowers Distinguished Professor. “These scientists have spent years unraveling the many potential roles of ouabain and how it works, and now we are beginning to see the fruits of their labor.”
Caffeine affects boys and girls differently after puberty
Caffeine intake by children and adolescents has been rising for decades, due in large part to the popularity of caffeinated sodas and energy drinks, which now are marketed to children as young as four. Despite this, there is little research on the effects of caffeine on young people.
One researcher who is conducting such investigations is Jennifer Temple, PhD, associate professor in the Department of Exercise and Nutrition Sciences, University at Buffalo School of Public Health and Health Professions.
Her new study finds that after puberty, boys and girls experience different heart rate and blood pressure changes after consuming caffeine. Girls also experience some differences in caffeine effect during their menstrual cycles.
The study, “Cardiovascular Responses to Caffeine by Gender and Pubertal Stage,” will be published online June 16 in the July 2014 edition of the journal Pediatrics.
Past studies, including those by this research team, have shown that caffeine increases blood pressure and decreases heart rate in children, teens and adults, including pre-adolescent boys and girls. The purpose here was to learn whether gender differences in cardiovascular responses to caffeine emerge after puberty and if those responses differ across phases of the menstrual cycle.
Temple says, “We found an interaction between gender and caffeine dose, with boys having a greater response to caffeine than girls, as well as interactions between pubertal phase, gender and caffeine dose, with gender differences present in post-pubertal, but not in pre-pubertal, participants.
“Finally,” she says, “we found differences in responses to caffeine across the menstrual cycle in post-pubertal girls, with decreases in heart rate that were greater in the mid-luteal phase and blood pressure increases that were greater in the mid-follicular phase of the menstrual cycle.
“In this study, we were looking exclusively into the physical results of caffeine ingestion,” she says.
Phases of the menstrual cycle, marked by changing levels of hormones, are the follicular phase, which begins on the first day of menstruation and ends with ovulation, and the luteal phase, which follows ovulation and is marked by significantly higher levels of progesterone than the previous phase.
Future research in this area will determine the extent to which gender differences are mediated by physiological factors such as steroid hormone level or by differences in patterns of caffeine use, caffeine use by peers or more autonomy and control over beverage purchases, Temple says.
This double-blind, placebo-controlled, dose-response study was funded by a grant from the National Institute on Drug Abuse of the National Institutes of Health.
It examined heart rate and blood pressure before and after administration of placebo and two doses of caffeine (1 and 2 mg/kg) in pre-pubertal (8- to 9-year-old; n = 52) and post-pubertal (15- to 17-year-old; n = 49) boys (n = 54) and girls (n = 47).
Music can be soothing or stirring, it can make us dance or make us sad. Blood pressure, heartbeat, respiration and even body temperature – music affects the body in a variety of ways. It triggers especially powerful physical reactions in pregnant women. Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig have discovered that pregnant women compared to their non-pregnant counterparts rate music as more intensely pleasant and unpleasant, associated with greater changes in blood pressure. Music appears to have an especially strong influence on pregnant women, a fact that may relate to a prenatal conditioning of the fetus to music.
For their study, the Max Planck researchers played short musical sequences of 10 or 30 seconds’ duration to female volunteers. They changed the passages and played them backwards or incorporated dissonances. By doing so, they distorted the originally lively instrumental pieces and made listening to them less pleasant.
The pregnant women rated the pieces of music slightly differently, they perceived the pleasant music as more pleasant and the unpleasant as more unpleasant. The blood pressure response to music was much stronger in the pregnant group. Forward-dissonant music produced a particularly pronounced fall in blood pressure, whereas backwards-dissonant music led to a higher blood pressure after 10 seconds and a lower one after 30 seconds. “Thus, unpleasant music does not cause an across-the-board increase in blood pressure, unlike some other stress factors”, says Tom Fritz of the Max Planck Institute in Leipzig. “Instead, the body’s response is just as dynamic as the music itself.”
According to the results, music is a very special stimulus for pregnant women, to which they react strongly. “Every acoustic manipulation of music affects blood pressure in pregnant women far more intensely than in non-pregnant women”, says Fritz. Why music has such a strong physiological influence on pregnant woman is still unknown. Originally, the scientists suspected the hormone oestrogen to play a mayor part in this process, because it has an influence on the brain’s reward system, which is responsible for the pleasant sensations experienced while listening to music. However, non-pregnant women showed constant physiological responses throughout the contraceptive cycle, which made them subject to fluctuations in oestrogen levels. “Either oestrogen levels are generally too low in non-pregnant women, or other physiological changes during pregnancy are responsible for this effect”, explains Fritz.
The researchers suspect that foetuses are conditioned to music perception while still in the womb by the observed intense physiological music responses of the mothers. From 28 weeks, i.e. at the start of the third trimester of pregnancy, the heart rate of the foetus already changes when it hears a familiar song. From 35 weeks, there is even a change in its movement patterns.
Anaesthetic technique important to prevent damage to brain
Researchers at the University of Adelaide have discovered that a commonly used anaesthetic technique to reduce the blood pressure of patients undergoing surgery could increase the risk of starving the brain of oxygen.
Reducing blood pressure is important in a wide range of surgeries - such as sinus, shoulder, back and brain operations - and is especially useful for improving visibility for surgeons, by helping to remove excess blood from the site being operated on.
There are many different techniques used to lower patients’ blood pressure for surgery - one of them is known as hypotensive anaesthesia, which slows the arterial blood pressure by up to 40%.
Professor PJ Wormald, a sinus, head and neck surgeon from the University’s Discipline of Surgery, based at the Queen Elizabeth Hospital, led a world-first study looking at both the effectiveness of hypotensive anaesthesia from the surgeon’s point of view and its impact on the patients.
The study followed 32 patients who underwent endoscopic sinus surgery. The results have now been published online in the journal The Laryngoscope.
"There is an important balance in anaesthesia where the blood pressure is lowered so that the surgeon has good visibility and is able to perform surgery safely. There are numerous sensitive areas in sinus surgery - the brain, the eye and large vessels such as the carotid. However, if the blood pressure is lowered too far this may cause damage to the brain and other organs," says Professor Wormald.
"We know from previous research that a person’s brain undergoing anaesthesia has lower metabolic requirements than the awake brain, and therefore it can withstand greater reductions in blood flow.
"There is also a widely accepted concept that the brain has the ability to autoregulate - to adapt and maintain a constant blood flow as needed, despite a wide range of blood pressure conditions. Our studies challenge this; they show that the brain can only autoregulate up to a point, and cannot completely adapt to such low blood pressures.
"This drop in blood pressure poses a risk of starving the brain of much-needed oxygen and nutrients, which could result in injury. There have been cases, for example, where patients have reported memory loss following surgery.
"Given that hypotensive anaesthesia is a widely used technique, not just in sinus surgery but in many different types of surgery, we’ve made recommendations in our paper that suggest a safer approach to this technique. This would reduce risk to the patient while enabling the surgeon to carry out their work effectively," Professor Wormald says.
(Image: Shutterstock)
High Blood Pressure in Middle Age Versus Old Age May Better Predict Memory Loss
People in middle age who have a high blood pressure measure called pulse pressure are more likely to have biomarkers of Alzheimer’s disease in their spinal fluid than those with lower pulse pressure, according to research published in the November 13, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology.
Pulse pressure is the systolic pressure, or the top number in a blood pressure reading, minus the diastolic, or the bottom number. Pulse pressure increases with age and is an index of the aging of the vascular system.
The study involved 177 people ages 55 to 100 with no symptoms of Alzheimer’s disease. Participants had their pulse pressure taken and lumbar punctures to obtain spinal fluid.
The study found that people who have higher pulse pressure are more likely to have the Alzheimer’s biomarkers amyloid beta, or plaques, and p-tau protein, or tangles, in their cerebral spinal fluid than those with lower pulse pressure. For every 10 point rise in pulse pressure, the average level of p-tau protein in the spinal fluid rose by 1.5 picograms per millileter. A picogram is one trillionth of a gram.
“These results suggest that the forces involved in blood circulation may be related to the development of the hallmark Alzheimer’s disease signs that cause loss of brain cells,” said study author Daniel A. Nation, PhD, of the VA San Diego Healthcare System.
The relationship was found in people age 55 to 70, but not in people age 70 to 100.
“This is consistent with findings indicating that high blood pressure in middle age is a better predictor of later problems with memory and thinking skills and loss of brain cells than high blood pressure in old age,” Nation said.
Happiness lowers blood pressure
A synthetic gene module controlled by the happiness hormone dopamine produces an agent that lowers blood pressure. This opens up new avenues for therapies that are remote-controlled via the subsconscious.
The endogenous hormone dopamine triggers feelings of happiness. While its release is induced, among other things, by the “feel-good” classics sex, drugs or food, the brain does not content itself with a kick; it remembers the state of happiness and keeps wanting to achieve it again. Dopamine enables us to make the “right” decisions in order to experience even more moments of happiness.
Biological components reconnected
Now a team of researchers headed by ETH-Zurich professor Martin Fussenegger from the Department of Biosystems Science and Engineering (D-BSSE) in Basel has discovered a way to use the body’s dopamine system therapeutically. The researchers have created a new genetic module that can be controlled via dopamine. The feel-good messenger molecule activates the module depending on the dosage. In response to an increase in the dopamine level in the blood, the module produces the desired active agent.
The module consists of several biological components of the human organism, which are interconnected to form a synthetic signalling cascade. Dopamine receptors are found at the beginning of the cascade as sensors. A particular agent is produced as an end product: either a model protein called SEAP or ANP, a powerful vasodilator lowering blood pressure. The researchers placed these signal cascades in human cells, so-called HEK cells, around 100,000 of which were in turn inserted into capsules. These were then implanted in the abdomens of mice.
Contact with females activates module
These animals were subsequently exposed to situations that corresponded to their central reward system, such as sexual arousal, which a female mouse triggered in males, the injection of the drug methamphetamine or the drinking of golden syrup. In each case, the mouse brain responded with a “state of happiness”, the formation of dopamine and its release into the blood via the peripheral nervous system. In mice which received different concentrations of golden syrup, the “state of happiness” varied: the more the sugar was diluted, the smaller the amount of dopamine and thus the active agent that circulated in the blood. “This shows that dopamine does not merely switch our module on and off, but also that it responds based on the concentration of the happiness hormone,” says Fussenegger.
In another step, the scientists linked the dopamine sensor module to the production of the antihypertensive agent ANP and implanted the customised cells in the abdomens of hypertensive male mice. Contact with a female mouse triggered such feelings of happiness in the males that the dopamine-induced ANP production corrected the hypertension and the blood pressure even reached a normal level.
Serum dopamine linked to brain
Based on their experiments, the researchers were also able to demonstrate that dopamine is not only formed in the brain in corresponding feel-good situations, but also in nerves in the vegetative system, the so-called sympathetic nervous system, which are closely knit around blood vessels. The brain is interlinked with the rest of the body via the sympathetic nervous system, despite the fact that the brain is unable to release “its” dopamine directly into the circulation due to the blood-brain barrier. Dopamine receptors have also been known to exist in body tissue such as the kidneys, adrenalin glands or on blood vessels, as well as in the brain.
Dopamine, which circulates in the blood serum, regulates the breathing and the blood sugar balance. For a long time, it was thus assumed that the activities of brain and serum dopamine were connected. The fact that the ETH-Zurich researchers in Basel have now managed to demonstrate this connection deepens our understanding of the body’s reward system.
Eating as therapeutic input
Martin Fussenegger says that eating, for instance, can be seen as therapeutic input thanks to this module. “Using the gene network, we link up with the normal reward system,” he explains. Good food triggers feelings of happiness, which activate the module and intervene in a process that is normally only controlled by the subconscious. As a result, daily activities could be used for therapeutic interventions.
For the time being, however, the dopamine hypertension model is only a prototype. With their work, the scientists have proved that they can intervene in the body’s reward system as a result. Nonetheless, it is more than merely an idea or experiment in living cells. “It works in a mouse model that simulates a human disease and the components we used to produce the module also came from humans.” When and whether a treatment based on the happiness hormone will hit the market, however, remains uncertain. The development of prototypes into a marketable product takes years or even decades.
Further reading
Rössger K, Charpin-El-Hamri G & Fussenegger M. Reward-based hypertension control by a synthetic brain-dopamine interface. PNAS Early Edition, online 14th Oct. 2013.
Omega-3 removes ADHD symptoms
A new multidisciplinary study shows a clear connection between the intake of omega-3 fatty acids and a decline in ADHD symptoms in rats.
Researchers at the University of Oslo have observed the behaviour of rats and have analyzed biochemical processes in their brains. The results show a clear improvement in ADHD-related behaviour from supplements of omega-3 fatty acids, as well as a faster turnover of the signal substances dopamine, serotonin and glutamate in the nervous system. There are, however, clear sex differences: a better effect from omega-3 fatty acids is achieved in male rats than in female.
Unknown biology behind ADHD
Currently the psychiatric diagnosis ADHD (Attention Deficit/Hyperactivity Disorder) is purely based on behavioural criteria, while the molecular genetic background for the illness is largely unknown. The new findings indicate that ADHD has a biological component and that the intake of omega-3 may influence ADHD symptoms.
“In some research environments it is controversial to suggest that ADHD has something to do with biology. But we have without a doubt found molecular changes in the brain after rats with ADHD were given omega-3,” says Ivar Walaas, Professor of Biochemistry.
The fact that omega-3 can reduce ADHD behaviour in rats has also been indicated in previous international studies. What is unique about the study in question is a multidisciplinarity that has not previously been seen, with contributions from behavioural science in medicine as well as from psychology, nutritional science and biochemistry.
Hyperactive rats
The rats used in the study are called SHR rats – spontaneously hypertensive rats. Although this is primarily a common type of rat, random mutations in their genes have resulted in genetic damage that produces high blood pressure. It is therefore first and foremost blood-pressure researchers who have so far been interested in these rats.
However, the rats do not suffer from high blood pressure until they have reached puberty. Before that age they present totally different symptoms – namely hyperactivity, poor ability to concentrate and impulsiveness. It is exactly these three criteria that form the basis for making the ADHD diagnosis in humans. The animals also react to Ritalin, the central nervous system stimulant, in the same way as humans with ADHD: the hyperactive responses are stabilized. SHR rats are therefore increasingly used in research as a model for ADHD.
Supplements as early as the foetal stage
Researchers believe that omega-3 can have an effect from the very beginning of life. Omega-3 was therefore added to the food given to mother rats before they were impregnated, and this continued throughout their entire pregnancy and while they fed their young. The baby rats were also given omega-3 in their own food after they were separated from their mother at the age of 20 days. Another group of mother rats were given food that did not have omega-3 added, thus creating a control group of SHR offspring that had not been given these fatty acids at the foetal stage or later.
The researchers started to analyze the behaviour of the offspring some days after they were separated from the mother. They studied behaviour driven by reward as well as spontaneous behaviour. Substantial differences were noted for both types of behaviour between the rats that had been given the omega-3 supplement as foetuses and as baby rats and those that had not.
Rewards made male rats more concentrated
The reward-driven behaviour was such that the rats were allowed access to a drop of water each time they pressed an illuminated button. The ADHD rats that had not been given omega-3 could not concentrate on pressing the button, whereas the rats that had been brought up on omega-3 easily managed to hold their concentration for the seconds this takes and were able to enjoy a delicious drop of water as a reward.
Surprisingly enough, it was only male rats that showed an improvement in reward-driven behaviour. However, with regard to the rats’ spontaneous behavior, the same type of reduction in hyperactivity and attention difficulties was noted in both male and female rats that had been given the omega-3 supplement.
Changes in brain chemistry
Professor Walaas and his research group became involved in the study at this point in order to analyze the molecular processes in the rats’ brains.
The group analyzed the level of the chemical connections in the brain, the so-called neurotransmitters that transfer nerve impulses from one nerve cell to another. The researchers measured how much of the neurotransmitters such as dopamine, serotonin and glutamate was released and broken down within the nerve fibres. A key player in this work was Kine S. Dervola, PhD candidate, who reports clear sex differences in the turnover of the neurotransmitters – just as there had been in the reward-driven behaviour.
“We saw that the turnover of dopamine and serotonin took place much faster among the male rats that had been given omega-3 than among those that had not. For serotonin the turnover ratio was three times higher, and for dopamine it was just over two and a half times higher. These effects were not observed among the female rats. When we measured the turnover of glutamate, however, we saw that both sexes showed a small increase in turnover,” Ms Dervola tells us.
Transferrable to humans?
The researchers are cautious about drawing conclusions as to whether the results can be transferred to humans.
“In the first place there is of course a difference between rats and humans, and secondly the rats are sick at the outset. Thirdly the causes of ADHD in humans are in no way mapped sufficiently well. But the end result of what takes place in the brains of both rats and humans with ADHD is hyperactivity, poor ability to concentrate and impulsiveness,” says Professor Walaas, and concludes:
“Giving priority to basic research like this will greatly increase our detailed knowledge of ADHD.”
Reference:
Dervola, Kine-Susann Noren; Roberg, Bjørg Åse; Wøien, Grete; Bogen, Inger Lise; Sandvik, Torbjørn; Sagvolden, Terje; Drevon, Christian A, Espen B. Johansen and Sven Ivar Walaas (2012). Marine omega-3 polyunsaturated fatty acids induce sex-specific changes in reinforcer-controlled behavior and neurotransmitter metabolism in a spontaneously hypertensive rat model of ADHD. Behavioral and Brain Functions. ISSN 1744-9081. 8(56).
(Source: med.uio.no)
Increased fluctuation in blood pressure linked to impaired cognitive function in older people
Higher variability in visit-to-visit blood pressure readings, independent of average blood pressure, could be related to impaired cognitive function in old age in those already at high risk of cardiovascular disease, suggests a paper published today on BMJ.
There is increasing evidence that vascular factors contribute in development and progression of dementia. This is of special interest as cardiovascular factors may be amendable and thus potential targets to reduce cognitive decline and the incidence of dementia. Visit-to-visit blood pressure variability has been linked to cerebrovascular damage (relating to the brain and its blood vessels). It has also been shown that this variability can increase the risk of stroke.
It has been suggested that higher blood pressure variability might potentially lead to cognitive impairment through changes in the brain structures.
Researchers from the Leiden University Medical Center (Netherlands), University College Cork (Ireland) and the Glasgow University (UK) therefore investigated the association of visit-to-visit blood pressure variability (independent of average blood pressure) with cognitive function in older subjects at high risk of cardiovascular disease.
All data were obtained from the PROSPER study, which investigated the effect of statins in prevention of vascular events in older men and women. This study took data on 5,461 individuals aged 70-82 years old in Ireland, Scotland and the Netherlands. Average follow-up was three years.
Both systolic (peak pressure) and diastolic (minimum pressure) blood pressures were measured every three months in the same clinical setting. The variability between these measurements were calculated and used in the analyses.
The study used data on cognitive function where the following was tested: selective attention and reaction time; general cognitive speed; immediate and delayed memory performance.
Results showed that visit-to-visit blood pressure variability was associated with worse performance on all cognitive tests. The results were consistent after adjusting for cardiovascular disease and other risk factors.
The main findings of the study were: higher visit-to-visit blood pressure variability is associated with worse performance in different cognitive tests; higher variability is associated with higher risk of stroke and both these associations are independent of various cardiovascular risk factors, in particular, average blood pressure.
Researcher Simon Mooijaart, (Leiden University Medical Centre, Leiden, the Netherlands) says that by using a population of “over five thousand participants and over three years of blood pressure measurements, we showed that high visit-to-visit systolic and diastolic blood pressure variability associates with worse performance in different domains of cognitive function including selection attention, processing speed, immediate verbal memory and delayed verbal memory”. The researchers do add though that it is still unclear whether higher blood pressure variability is a cause or consequence of impaired cognitive function.
They suggest several explanations for their findings: firstly that blood pressure variability and cognitive impairment could stem from a common cause, with cardiovascular risk factors being the most likely candidate; secondly that variability might reflect a long term instability in the regulation of blood pressure and blood flow to the key organs in the body; thirdly that exaggerated fluctuations in blood pressure could result in the brain not receiving enough blood, which can cause brain injury, leading to impairment of cognitive function.
The researchers conclude that “higher visit-to-visit blood pressure variability independent of average blood pressure might be a potential risk factor with worse cognitive performance in older subjects at high risk of cardiovascular disease”. Given that dementia is a major public health issue, they say that further interventional studies are warranted to establish whether reducing blood pressure variability can decrease the risk of cognitive impairment in old age.
(Source: eurekalert.org)
Low Diastolic Blood Pressure May Be Associated With Brain Atrophy
Low baseline diastolic blood pressure (DBP) appears to be associated with brain atrophy in patients with arterial disease, whenever declining levels of blood pressure (BP) over time among patients who had a higher baseline BP were associated with less progression of atrophy, according to a report published Online First by JAMA Neurology, a JAMA Network publication.
(Image: Wikimedia Commons)
“Studies have shown that both high and low blood pressure (BP) may play a role in the etiology of brain atrophy. High BP in midlife has been associated with more brain atrophy later in life, whereas studies in older populations have shown a relation between low BP and more brain atrophy. Yet, prospective evidence is limited, and the relation remains unclear in patients with manifest arterial disease,” according to the study.
Hadassa M. Jochemsen, M.D., of University Medical Center Utrecht, the Netherlands, and colleagues examined the association of baseline BP and change in BP over time with the progression of brain atrophy in 663 patients (average age 57 years; 81 percent male). The patients had coronary artery disease, cerebrovascular disease, peripheral artery disease or abdominal aortic aneurysm.
According to the results, patients with lower baseline DBP or mean arterial pressure (MAP) had more progression of subcortical (the area beneath the cortex of the brain) atrophy. In patients with higher BP (DBP, MAP or systolic BP), those with declining BP levels over time had less progression of subcortical atrophy compared with those with rising BP levels.
“This could imply that BP lowering is beneficial in patients with higher BP levels, but one should be cautious with further BP lowering in patients who already have low BP,” the study authors conclude.
(Source: media.jamanetwork.com)
![Microbleeding in Brain May Be Behind Senior Moments
People may grow wiser with age, but they don’t grow smarter. Many of our mental abilities decline after midlife, and now researchers say that they’ve fingered a culprit. A study presented here last week at the annual meeting of the Association for Psychological Science points to microbleeding in the brain caused by stiffening arteries. The finding may lead to new therapies to combat senior moments.
This isn’t the first time that microbleeds have been suspected as a cause of cognitive decline. “We have known [about them] for some time thanks to neuroimaging studies,” says Matthew Pase, a psychology Ph.D. student at Swinburne University of Technology in Melbourne, Australia. The brains of older people are sometimes peppered with dark splotches where blood vessels have burst and created tiny dead zones of tissue. How important these microbleeds are to cognitive decline, and what causes them, have remained open questions, however.
Pase wondered if high blood pressure might be behind the microbleeds. The brain is a very blood-hungry organ, he notes. “It accounts for only 2% of the body weight yet receives 15% of the cardiac output and consumes 20% of the body’s oxygen expenditure.” Rather than getting the oxygen in pulses, the brain needs a smooth, continuous supply. So the aorta, the largest blood vessel branching off the heart, smooths out blood pressure before it reaches the brain by absorbing the pressure with its flexible walls. But as people age, the aorta stiffens. That translates to higher pressure on the brain, especially during stress. The pulse of blood can be strong enough to burst vessels in the brain, resulting in microbleeds.
A stumbling block has been accurately measuring the blood pressure that the brain experiences. The hand-pumped armband devices commonly used in doctor’s offices measure only the local pressure of blood in the arm, known as the brachial pressure. To calculate aorta stiffness, the “central blood pressure” in the aorta is needed. A technique for measuring central blood pressure was developed in the late 1990s, called applanation tonometry (AT). It works by comparing the pressure wave of blood from the heart with the reflected pressure wave from the vessels farthest from the heart—the aorta stiffness is calculated from the difference in pressure from the two. Devices for measuring AT have appeared on the market that are fast and painless.
To see if central blood pressure and aorta stiffening are related to cognitive abilities, Pase and colleagues recruited 493 people in Melbourne, 20 to 82 years old. They made traditional blood pressure measurements and also used AT to measure central blood pressure and estimate aorta stiffness. They also measured their subjects’ cognitive abilities with a standard battery of computer tests.
Central blood pressure and aorta stiffness alone were sensitive predictors of cognitive abilities, Pase reported at the meeting. The higher the central pressure and aorta stiffness, the worse people tended to perform on tests of visual processing and memory. The traditional measures of blood pressure in the arm were correlated with only scores on one test of visual processing.
To prove that aorta stiffening causes microbleeds, the researchers will need to repeat the experiment on the same people over the course of several years, using neuroimaging as well to establish that aorta stiffening leads to both microbleeding and cognitive decline. Pase notes that other causes of microbleeding have been proposed, such as weakening of blood vessels in the brain.
"This work is so important because the problem is so pervasive," says Earl Hunt, a veteran intelligence researcher at the University of Washington, Seattle, who was not involved in the work. The individual effects of these microbleeds are probably too small to measure. "But even a trifling difference multiplied a million times is big," he says. Pase’s collaborator at Swinburne, Con Stough, is now leading a study of how to prevent microbleeding through dietary supplements. He proposes that the elasticity of the aorta could be preserved by providing fatty acids or antioxidants that help maintain its structure. The results are expected in 2015.](http://41.media.tumblr.com/94707d203b7f0098726d72268ecf4037/tumblr_mnriiiQLsd1rog5d1o1_500.jpg)
Microbleeding in Brain May Be Behind Senior Moments
People may grow wiser with age, but they don’t grow smarter. Many of our mental abilities decline after midlife, and now researchers say that they’ve fingered a culprit. A study presented here last week at the annual meeting of the Association for Psychological Science points to microbleeding in the brain caused by stiffening arteries. The finding may lead to new therapies to combat senior moments.
This isn’t the first time that microbleeds have been suspected as a cause of cognitive decline. “We have known [about them] for some time thanks to neuroimaging studies,” says Matthew Pase, a psychology Ph.D. student at Swinburne University of Technology in Melbourne, Australia. The brains of older people are sometimes peppered with dark splotches where blood vessels have burst and created tiny dead zones of tissue. How important these microbleeds are to cognitive decline, and what causes them, have remained open questions, however.
Pase wondered if high blood pressure might be behind the microbleeds. The brain is a very blood-hungry organ, he notes. “It accounts for only 2% of the body weight yet receives 15% of the cardiac output and consumes 20% of the body’s oxygen expenditure.” Rather than getting the oxygen in pulses, the brain needs a smooth, continuous supply. So the aorta, the largest blood vessel branching off the heart, smooths out blood pressure before it reaches the brain by absorbing the pressure with its flexible walls. But as people age, the aorta stiffens. That translates to higher pressure on the brain, especially during stress. The pulse of blood can be strong enough to burst vessels in the brain, resulting in microbleeds.
A stumbling block has been accurately measuring the blood pressure that the brain experiences. The hand-pumped armband devices commonly used in doctor’s offices measure only the local pressure of blood in the arm, known as the brachial pressure. To calculate aorta stiffness, the “central blood pressure” in the aorta is needed. A technique for measuring central blood pressure was developed in the late 1990s, called applanation tonometry (AT). It works by comparing the pressure wave of blood from the heart with the reflected pressure wave from the vessels farthest from the heart—the aorta stiffness is calculated from the difference in pressure from the two. Devices for measuring AT have appeared on the market that are fast and painless.
To see if central blood pressure and aorta stiffening are related to cognitive abilities, Pase and colleagues recruited 493 people in Melbourne, 20 to 82 years old. They made traditional blood pressure measurements and also used AT to measure central blood pressure and estimate aorta stiffness. They also measured their subjects’ cognitive abilities with a standard battery of computer tests.
Central blood pressure and aorta stiffness alone were sensitive predictors of cognitive abilities, Pase reported at the meeting. The higher the central pressure and aorta stiffness, the worse people tended to perform on tests of visual processing and memory. The traditional measures of blood pressure in the arm were correlated with only scores on one test of visual processing.
To prove that aorta stiffening causes microbleeds, the researchers will need to repeat the experiment on the same people over the course of several years, using neuroimaging as well to establish that aorta stiffening leads to both microbleeding and cognitive decline. Pase notes that other causes of microbleeding have been proposed, such as weakening of blood vessels in the brain.
"This work is so important because the problem is so pervasive," says Earl Hunt, a veteran intelligence researcher at the University of Washington, Seattle, who was not involved in the work. The individual effects of these microbleeds are probably too small to measure. "But even a trifling difference multiplied a million times is big," he says. Pase’s collaborator at Swinburne, Con Stough, is now leading a study of how to prevent microbleeding through dietary supplements. He proposes that the elasticity of the aorta could be preserved by providing fatty acids or antioxidants that help maintain its structure. The results are expected in 2015.