Thursday, December 12, 2019
Scientists have known for decades that aerobic exercise strengthens the brain and contributes to the growth of new neurons, but few studies have examined how yoga affects the brain. A review of the science finds evidence that yoga enhances many of the same brain structures and functions that benefit from aerobic exercise.
The review, published in the journal Brain Plasticity, focused on 11 studies of the relationship between yoga practice and brain health. Five of the studies engaged individuals with no background in yoga practice in one or more yoga sessions per week over a period of 10-24 weeks, comparing brain health at the beginning and end of the intervention. The other studies measured brain differences between individuals who regularly practice yoga and those who don't.
Each of the studies used brain-imaging techniques such as MRI, functional MRI or single-photon emission computerized tomography. All involved Hatha yoga, which includes body movements, meditation and breathing exercises.
"From these 11 studies, we identified some brain regions that consistently come up, and they are surprisingly not very different from what we see with exercise research," said University of Illinois kinesiology and community health professor Neha Gothe, who led the research with Wayne State University psychology professor Jessica Damoiseaux.
"For example, we see increases in the volume of the hippocampus with yoga practice," Gothe said. Many studies looking at the brain effects of aerobic exercise have shown a similar increase in hippocampus size over time, she said.
The hippocampus is involved in memory processing and is known to shrink with age, Gothe said. "It is also the structure that is first affected in dementia and Alzheimer's disease."
Though many of the studies are exploratory and not conclusive, the research points to other important brain changes associated with regular yoga practice, Damoiseaux said. The amygdala, a brain structure that contributes to emotional regulation, tends to be larger in yoga practitioners than in their peers who do not practice yoga. The prefrontal cortex, cingulate cortex and brain networks such as the default mode network also tend to be larger or more efficient in those who regularly practice yoga.
"The prefrontal cortex, a brain region just behind the forehead, is essential to planning, decision-making, multitasking, thinking about your options and picking the right option," Damoiseaux said. "The default mode network is a set of brain regions involved in thinking about the self, planning and memory."
Like the amygdala, the cingulate cortex is part of the limbic system, a circuit of structures that plays a key role in emotional regulation, learning and memory, she said.
The studies also find that the brain changes seen in individuals practicing yoga are associated with better performance on cognitive tests or measures of emotional regulation.
The discovery that yoga may have similar effects on the brain to aerobic exercise is intriguing and warrants more study, Gothe said.
"Yoga is not aerobic in nature, so there must be other mechanisms leading to these brain changes," she said. "So far, we don't have the evidence to identify what those mechanisms are."
She suspects that enhancing emotional regulation is a key to yoga's positive effects on the brain. Studies link stress in humans and animals to shrinkage of the hippocampus and poorer performance on tests of memory, for example, she said.
"In one of my previous studies, we were looking at how yoga changes the cortisol stress response," Gothe said. "We found that those who had done yoga for eight weeks had an attenuated cortisol response to stress that was associated with better performance on tests of decision-making, task-switching and attention."
Yoga helps people with or without anxiety disorders manage their stress, Gothe said.
"The practice of yoga helps improve emotional regulation to reduce stress, anxiety and depression," she said. "And that seems to improve brain functioning."
The researchers say there is a need for more - and more rigorous - research into yoga's effects on the brain. They recommend large intervention studies that engage participants in yoga for months, match yoga groups with active control groups, and measure changes in the brain and performance on cognitive tests using standard approaches that allow for easy comparisons with other types of exercise.
"The science is pointing to yoga being beneficial for healthy brain function, but we need more rigorous and well-controlled intervention studies to confirm these initial findings," Damoiseaux said.
If you're prone to depression, this holiday season you might want to say "bah humbug" to offers of sugar plum pudding, caramel corn and chocolate babka.
A new study from a team of clinical psychologists at the University of Kansas suggests eating added sugars - common in so many holiday foods - can trigger metabolic, inflammatory and neurobiological processes tied to depressive illness. The work is published in the journal Medical Hypotheses.
Coupled with dwindling light in wintertime and corresponding changes in sleep patterns, high sugar consumption could result in a "perfect storm" that adversely affects mental health, according to the researchers.
"For many people, reduced sunlight exposure during the winter will throw off circadian rhythms, disrupting healthy sleep and pushing five to 10% of the population into a full-blown episode of clinical depression," said Stephen Ilardi, KU associate professor of clinical psychology.
Ilardi, who coauthored the study with KU graduate students Daniel Reis (lead author), Michael Namekata, Erik Wing and Carina Fowler (now of Duke University), said these symptoms of "winter-onset depression" could prompt people to consume more sweets.
"One common characteristic of winter-onset depression is craving sugar," he said. "So, we've got up to 30% of the population suffering from at least some symptoms of winter-onset depression, causing them to crave carbs - and now they're constantly confronted with holiday sweets."
Ilardi said avoidance of added dietary sugar might be especially challenging because sugar offers an initial mood boost, leading some with depressive illness to seek its temporary emotional lift.
"When we consume sweets, they act like a drug," said the KU researcher, who also is author of "The Depression Cure" (First De Capo Press, 2009). "They have an immediate mood-elevating effect, but in high doses they can also have a paradoxical, pernicious longer-term consequence of making mood worse, reducing well-being, elevating inflammation and causing weight gain."
The investigators reached their conclusions by analyzing a wide range of research on the physiological and psychological effects of consuming added sugar, including the Women's Health Initiative Observational Study, the NIH-AARP Diet and Health Study, a study of Spanish university graduates, and studies of Australian and Chinese soda-drinkers.
Ilardi cautioned it might be appropriate to view added sugar, at high enough levels, as physically and psychologically harmful, akin to drinking a little too much liquor.
"We have pretty good evidence that one alcoholic drink a day is safe, and it might have beneficial effect for some people," he said. "Alcohol is basically pure calories, pure energy, non-nutritive and super toxic at high doses. Sugars are very similar. We're learning when it comes to depression, people who optimize their diet should provide all the nutrients the brain needs and mostly avoid these potential toxins."
The researchers found inflammation is the most important physiological effect of dietary sugar related to mental health and depressive disorder.
"A large subset of people with depression have high levels of systemic inflammation," said Ilardi. "When we think about inflammatory disease we think about things like diabetes and rheumatoid arthritis - diseases with a high level of systemic inflammation. We don't normally think about depression being in that category, but it turns out that it really is - not for everyone who's depressed, but for about half. We also know that inflammatory hormones can directly push the brain into a state of severe depression. So, an inflamed brain is typically a depressed brain. And added sugars have a pro-inflammatory effect on the body and brain."
Ilardi and his collaborators also identify sugar's impact on the microbiome as a potential contributor to depression.
"Our bodies host over 10 trillion microbes and many of them know how to hack into the brain," Ilardi said. "The symbiotic microbial species, the beneficial microbes, basically hack the brain to enhance our well-being. They want us to thrive so they can thrive. But there are also some opportunistic species that can be thought of as more purely parasitic - they don't have our best interest in mind at all. Many of those parasitic microbes thrive on added sugars, and they can produce chemicals that push the brain in a state of anxiety and stress and depression. They're also highly inflammatory."
Ilardi recommended a minimally processed diet rich in plant-based foods and Omega-3 fatty acids for optimal psychological benefit. As for sugar, the KU researcher recommended caution - not just during the holidays, but year-round.
"There's no one-size-fits-all approach to predicting exactly how any person's body will react to any given food at any given dose," Ilardi stated. "As a conservative guideline, based on our current state of knowledge, there could be some risk associated with high-dose sugar intake - probably anything above the American Heart Association guideline, which is 25 grams of added sugars per day."
A recent study published in the journal Cephalalgia, the official journal of the International Headache Society, highlights an overlooked relationship between migraine and exercise. The study, entitled "Anxiety sensitivity and intentional avoidance of physical activity in women with probable migraine", was led by Samantha G Farris, from Rutgers, Department of Psychology, the State University of New Jersey, NJ, USA.
Migraine affects around 10-15% of the population around the globe, and among its most common diagnosis criteria include a throbbing, unilateral head pain, hypersensitivity to lights, sounds, odors, and aggravation by activity. Although regular aerobic exercise has been strongly recommended by clinicians as an adjuvant option for migraine prevention, for up to 1/3 of patients, physical exercise can be a trigger of migraine attacks, thus, it can instead be avoided as a strategy to manage migraine. As observed with other pain conditions, anxiety sensitivity, which refers to one's fear of experiencing anxiety arousal due to harmful physical, cognitive and socially-observable consequences, may be related to PA avoidance in migraine patients. This seems to be the true especially with vigorous PA, as this exercise intensity is perceived as potentially triggering or worsening of migraine attacks.
In this study, the researchers assessed 100 women with probable migraine, who filled an online survey covering anxiety sensitivity scores, intentional avoidance of moderate and vigorous physical activity (PA) in the past month, which was based on the Global Physical Activity Questionnaire (GPAQ), as well as the self-rated perception (0-100%) that PA would trigger a migraine attack and worse migraine symptoms.
The results showed that increased anxiety sensitivity scores associated with PA avoidance of both moderate and vigorous intensities. One-point increase in the anxiety sensitivity scale resulted in up to 5% increase in the odds for avoiding PA. Concerns about the physical consequences of bodily sensations (e.g. difficulty breathing) associated with a 7.5-fold higher odds for avoiding vigorous PA, while cognitive consequences of bodily sensations (e.g. inability to concentrate), which is thought to reflect headache-related disability, associated with a 5.2-fold higher odds for avoiding moderate PA. Anxiety sensitivity scores positively associated with stronger expectations of vigorous-intensity PA as a triggering and worsening factor for migraine.
This study revealed a relevant but overlooked aspect of migraine. Migraine is a highly prevalent and disabling neurological disorder, in which regular PA is part of current non-pharmacological treatment recommendations. As pointed out by the authors "Patients with migraine and elevated anxiety sensitivity could benefit from tailored, multi-component intervention, ideally including: Psychoeducation about the positive effect of PA on migraine and the detrimental effect of avoidance, feedback about the perceived versus actual rates of PA in triggering/worsening migraine, and use of gradual exposure to facilitate desensitization to avoided of PA and related bodily sensations."
Not getting enough water is enough to make you feel sluggish and give you a headache, but a new Penn State study suggests it may also relate to cognitive performance.
The researchers investigated whether hydration levels and water intake among older adults was related with their scores on several tests designed to measure cognitive function. They found that among women, lower hydration levels were associated with lower scores on a task designed to measure motor speed, sustained attention, and working memory. They did not find the same result for men.
The findings were recently published in the European Journal of Nutrition.
"The study gives us clues about how hydration and related drinking habits relate to cognition in older adults," said Hilary Bethancourt, a postdoctoral scholar in biobehavioral health and first author on the study. "This is important because older adults already face increased risk of cognitive decline with advancing age and are often less likely than younger adults to meet daily recommendations on water intake."
Asher Rosinger, Ann Atherton Hertzler Early Career Professor in Global Health, said the researchers found similar results when the participants were overhydrated.
"We found a trend suggesting overhydration may be just as detrimental to cognitive performance as dehydration for older adults," said Rosinger, who also directs the Water, Health, and Nutrition Laboratory and was senior author on the study. "Because of this, being in the 'sweet spot' of hydration seems to be best for cognitive function, especially for tasks requiring sustained attention."
According to the researchers, scientists have long suspected that dehydration may have an effect on cognitive performance. However, previous studies have largely focused on young, healthy people who are dehydrated after exercise and/or being in the heat.
Bethancourt said that because exercise and elevated ambient and body temperatures can have their own, independent effects on cognition, she and the other researchers were interested in the effects of day-to-day hydration status in the absence of exercise or heat stress, especially among older adults.
"As we age, our water reserves decline due to reductions in muscle mass, our kidneys become less effective at retaining water, and hormonal signals that trigger thirst and motivate water intake become blunted," Bethancourt said. "Therefore, we felt like it was particularly important to look at cognitive performance in relation to hydration status and water intake among older adults, who may be underhydrated on a regular basis."
For the study, the researchers used data from a nationally representative sample of 1271 women and 1235 men who were 60 years of age or older. Data were collected by the Nutrition and Health Examination Survey. Participants gave blood samples and were asked about all foods and drinks consumed the previous day. The researchers calculated hydration status based on concentrations of sodium, potassium, glucose, and urea nitrogen in participants' blood. Total water intake was measured as the combined liquid and moisture from all beverages and foods.
Participants also completed three tasks designed to measure different aspects of cognition, with the first two measuring verbal recall and verbal fluency, respectively.
A final task measured processing speed, sustained attention, and working memory. Participants were given a list of symbols, each matched with a number between one and nine. They were then given a list of numbers one through nine in random order and asked to draw the corresponding symbol for as many numbers as possible within two minutes.
Bethancourt said that when they first plotted the average test scores across different levels of hydration status and water intake, there appeared to be a distinct trend toward higher test scores in relation to adequate hydration and/or meeting recommended water intake. However, much of that was explained by other factors.
"Once we accounted for age, education, hours of sleep, physical activity level, and diabetes status and analyzed the data separately for men and women, the associations with hydration status and water intake were diminished," Bethancourt said. "A trend toward lower scores on the number-symbol test among women who were categorized as either underhydrated or overhydrated was the most prominent finding that remained after we accounted for other influential factors."
Bethancourt said that because the data was cross-sectional, they can't be sure whether suboptimal hydration levels are causing cognitive impairment or if people with impaired cognition are just more likely to be under- or overhydrated. The researchers were also unsure why they failed to see the same associations among men. Still, she said the results raise interesting questions.
"It was interesting that even though the test of attention, processing speed, and working memory took only a few minutes, it was the one most strongly associated with lower hydration levels," Bethancourt said. "Other research has similarly suggested that attention may be one of the cognitive domains most affected by hydration status. This left us wondering what the effects of inadequate hydration might be on more difficult tasks requiring longer periods of concentration and focus."
Rosinger said the findings suggest older adults may want to pay close attention to their hydration status, by both consuming enough liquids to avoid dehydration as well as ensuring adequate electrolyte balance to avoid overhydration.
"Because older adults may not necessarily feel thirsty when their body is reaching a state of underhydration and may be taking diuretics that can increase salt excretion, it is important for older adults and their physicians to better understand the symptoms of being both under- and overhydrated," said Rosinger.
W. Larry Kenney, Marie Underhill Noll Chair in Human Performance, and David M. Almeida, professor of human development and family studies, also participated in this work.
Wednesday, December 11, 2019
People who take long naps during the day or sleep nine or more hours at night may have an increased risk of stroke, according to a study published in the December 11, 2019, online issue of Neurology®, the medical journal of the American Academy of Neurology. People who took a regular midday nap lasting more than 90 minutes were 25 percent more likely to later have a stroke than people who took a regular nap lasting from one to 30 minutes. People who took no naps or took naps lasting from 31 minutes to one hour were no more likely to have a stroke than people who took naps lasting from one to 30 minutes.
"More research is needed to understand how taking long naps and sleeping longer hours at night may be tied to an increased risk of stroke, but previous studies have shown that long nappers and sleepers have unfavorable changes in their cholesterol levels and increased waist circumferences, both of which are risk factors for stroke," said study author Xiaomin Zhang, MD, PhD, of Huazhong University of Science and Technology in Wuhan, China. "In addition, long napping and sleeping may suggest an overall inactive lifestyle, which is also related to increased risk of stroke."
The study involved 31,750 people in China with an average age of 62. The people did not have any history of stroke or other major health problems at the start of the study. They were followed for an average of six years. During that time, there were 1,557 stroke cases.
The people were asked questions about their sleep and napping habits. Midday napping is common in China, Zhang said. Eight percent of the people took naps lasting more than 90 minutes. And 24 percent said they slept nine or more hours per night.
The study found that people who sleep nine or more hours per night are 23 percent more likely to later have a stroke than people who sleep seven to less than eight hours per night. People who sleep less than seven hours per night or between eight and less than nine hours per night were no more likely to have a stroke than those who slept from seven to less than eight hours per night.
The results were all adjusted for other factors that could affect the risk of stroke. These include high blood pressure, diabetes and smoking.
People who were both long nappers and long sleepers were 85 percent more likely to later have a stroke than people who were moderate sleepers and nappers.
The researchers also asked people about how well they slept. People who said their sleep quality was poor were 29 percent more likely to later have a stroke than people who said their sleep quality was good.
Of the long nappers, 1 percent of cases per person-years later had a stroke, compared to 0.7 percent of cases per person-years of the moderate nappers. The numbers were the same for the long and moderate sleepers, with 1 percent of cases per person-years compared to 0.7 percent of cases per person-years having a stroke.
"These results highlight the importance of moderate napping and sleeping duration and maintaining good sleep quality, especially in middle-age and older adults," Zhang said.
Zhang noted that the study does not prove cause and effect between long napping and sleeping and stroke. It only shows an association.
Limitations of the study include that information on sleep and napping was taken from questionnaires, not from recording people's actual sleep and information was not collected on sleep disorders such as snoring and sleep apnea. Also, the study involved older, healthy Chinese adults, so the results may not apply to other groups.
A new study conducted by researchers at Washington State University shows that individuals with chronic sleep-onset insomnia who pulled an all-nighter performed up to twice as bad on a reaction time task as healthy normal sleepers. Their findings were published today in the online journal Nature and Science of Sleep. Poor daytime functioning is a frequent complaint among those suffering from insomnia, said lead author Devon Hansen, an assistant professor in the Elson S. Floyd College of Medicine and a researcher in the WSU Sleep and Performance Research Center. However, previous studies have found that their daytime cognitive performance is not significantly degraded, seemingly suggesting that it is a perceived issue that does not reflect a real impairment. The WSU study of individuals with sleep-onset insomnia revealed that the impairment may in fact be real but hidden during the normal day--yet exposed after pulling an all-nighter, which impacted them much more than age-matched control subjects.
The finding caught the WSU research team by surprise.
"There has been a theory about what perpetuates insomnia that focuses on hyperarousal, an activation in their system that keeps those with insomnia from being able to wind down when they go to bed," Hansen said. "We thought that this hyperarousal would protect them to some extent and had hypothesized that their performance after a night of total sleep deprivation would be better than normal healthy sleepers. Instead, we found the exact opposite."
Hansen, who in a previous career worked as a therapist in a sleep clinic, said the study adds credibility to insomnia patients' experiences. She also said it serves as a warning to poor sleepers that they should try to maintain a regular sleep schedule and avoid pushing their limits by staying up all night.
The research team studied 14 volunteer participants. Half of the group consisted of individuals who had chronic sleep-onset insomnia, the inability to fall asleep within 30 minutes for at least three nights a week for more than three months. The other half were healthy normal sleepers who served as controls. The two groups of participants were matched in age, with all participants aged between 22 and 40 and an average age of 29 for both groups.
Participants spent a total of five days and four nights in the sleep laboratory. They were allowed to sleep normally during the first two nights. They were kept awake the next night and following day--totaling 38 hours of total sleep deprivation--followed by a night of recovery sleep.
During their time awake, participants completed a series of performance tasks every three hours. This included a widely used alertness test known as the psychomotor vigilance test (PVT), which measures participants' response times to visual stimuli that appear on a screen at random intervals. The researchers analyzed PVT data for lapses of attention (i.e., slow reaction times) and false starts (i.e., responses that occur before the stimulus appears), comparing the findings between the two groups both before and during sleep deprivation.
Before sleep deprivation, the insomnia group's performance on the PVT looked very similar to that of the control group. However, as soon as sleep deprivation started the researchers began to see a dramatic increase in lapses of attention and false starts in the insomnia group. At one point during the night, their performance was twice as bad as that of the healthy normal sleepers.
"Our study suggests that even with a few hours of sleep deprivation--which people routinely experience for work or family reasons--those with sleep-onset insomnia may be much more impaired than those who normally sleep well at night," Hansen said. "This may increase their risk of errors and accidents whenever time-sensitive performance is required, such as while driving or when focused on a safety-critical task."
Hansen cautioned that since their study looked specifically at individuals with sleep-onset insomnia, their findings may not hold up in other insomnia subtypes, such as sleep-maintenance insomnia--which is characterized by difficulty staying asleep--and terminal insomnia--which involves early-morning awakenings. She plans to repeat the study in those groups to find out.
Fatty liver disease affects about one in three Australians and is often associated with being overweight or obese. If left untreated, it can lead to liver cirrhosis, liver cancer and increase the risk of a heart attack.
But the remedy - to lose weight through diet or exercise - is often difficult to achieve for affected individuals.
In other words, it may not be laziness but lack of iron which is important for energy production that is stopping people with non-alcoholic liver disease from addressing their condition. -
This research indicates that people with the condition may be physiologically incapable of exercise due to iron not being available for the body to use normally, which is very similar to the effects observed in people who have a true iron deficiency.
The new research, under the direction of lead researcher Professor John Olynyk, will help guide future treatment for people with non-alcoholic fatty liver disease.
The body is like a car
ECU researchers measured the cardiovascular fitness of 848 17-year-old West Australians enrolled in the well known Raine Study and found that those with non-alcoholic fatty liver disease had lower physical work capacity independent of their weight.,
This reduced physical work capacity was also strongly related to parameters suggesting that iron is not being made available to the body for normal metabolism.
Professor John Olynyk said the study showed that people with non-alcoholic-fatty-liver disease had lower cardiovascular fitness, which was likely caused by a functional iron deficiency.
"We know that an iron deficiency can cause lethargy and fatigue, making it harder for people to exercise," he said.
"What is likely happening is that non-alcoholic fatty liver disease is impeding the body's ability to provide adequate iron into the blood to fuel processes such as energy and blood cell production.
"To use an analogy, if you imagine the body as a car and iron as its fuel, what is likely happening is that there is plenty of iron, or fuel in the tank, but the non-alcoholic fatty liver disease has caused the fuel line to shrink, so there's not enough fuel can get to the engine."
Diet before exercise
Professor Olynyk said the findings were useful for guiding the treatment of non-alcoholic fatty liver disease.
"The main treatment is lifestyle change aimed at reducing weight, primarily achieved through exercise and a modified diet," he said.
"In particular, there is evidence published by other investigators in the field that the Mediterranean diet can reduce the severity of non-alcoholic fatty liver disease. This is because it is high in foods like fruit and vegetables and whole grains, which have anti-inflammatory properties.
"This research shows that it may be more effective to first focus on new ways to improve the availability of iron to the body, enabling diet and physical activity to have better and more sustained effects on weight and the severity of their non-alcoholic fatty liver disease."