Wednesday, December 6, 2017

The human race has peaked



Humans may have reached their maximum limits for height, lifespan and physical performance. A recent review suggests humans have biological limitations, and that anthropogenic impacts on the environment - including climate change - could have a deleterious effect on these limits. Published in Frontiers in Physiology, this review is the first of its kind spanning 120 years worth of historical information, while considering the effects of both genetic and environmental parameters.

Despite stories that with each generation we will live longer and longer, this review suggests there may be a maximum threshold to our biological limits that we cannot exceed.

A transdisciplinary research team from across France studied trends emerging from historical records, concluding that there appears to be a plateau in the maximum biological limits for humans' height, age and physical abilities.

"These traits no longer increase, despite further continuous nutritional, medical, and scientific progress. This suggests that modern societies have allowed our species to reach its limits. We are the first generation to become aware of this" explains Professor Jean-François Toussaint from Paris Descartes University, France.

Rather than continually improving, we will see a shift in the proportion of the population reaching the previously recorded maximum limits. Examples of the effects of these plateaus will be evidenced with increasingly less sport records being broken and more people reaching but not exceeding the present highest life expectancy.

However, when researchers considered how environmental and genetic limitations combined may affect the ability for us to reach these upper limits, our effect on the environment was found to play a key role.

"This will be one of the biggest challenges of this century as the added pressure from anthropogenic activities will be responsible for damaging effects on human health and the environment." Prof. Toussaint predicts. "The current declines in human capacities we can see today are a sign that environmental changes, including climate, are already contributing to the increasing constraints we now have to consider."

"Observing decreasing tendencies may provide an early signal that something has changed but not for the better. Human height has decreased in the last decade in some African countries; this suggests some societies are no longer able to provide sufficient nutrition for each of their children and maintain the health of their younger inhabitants," Prof. Toussaint explains.

To avoid us being the cause of our own decline, the researchers hope their findings will encourage policymakers to focus on strategies for increasing quality of life and maximize the proportion of the population that can reach these maximum biological limits.

"Now that we know the limits of the human species, this can act as a clear goal for nations to ensure that human capacities reach their highest possible values for most of the population. With escalating environmental constraints, this may cost increasingly more energy and investment in order to balance the rising ecosystem pressures. However, if successful, we then should observe an incremental rise in mean values of height, lifespan and most human biomarkers." Prof. Toussaint warns however, "The utmost challenge is now to maintain these indices at high levels."

Some video games are good for older adults' brains


If you're between 55 and 75 years old, you may want to try playing 3D platform games like Super Mario 64 to stave off mild cognitive impairment and perhaps even prevent Alzheimer's disease.

That's the finding of a new Canadian study by Université de Montréal psychology professors Gregory West, Sylvie Belleville and Isabelle Peretz. Published in PLOS ONE, it was done in cooperation with the Institut universitaire de gériatrie de Montréal (IUGM), Benjamin Rich Zendel of Memorial University in Newfoundland, and Véronique Bohbot of Montreal's Douglas Hospital Research Centre.

In two separate studies, in 2014 and 2017, young adults in their twenties were asked to play 3D video games of logic and puzzles on platforms like Super Mario 64. Findings showed that the gray matter in their hippocampus increased after training.

The hippocampus is the region of the brain primarily associated with spatial and episodic memory, a key factor in long-term cognitive health. The gray matter it contains acts as a marker for neurological disorders that can occur over time, including mild cognitive impairment and Alzheimer's.

West and his colleagues wanted to see if the results could be replicated among healthy seniors.

The research team recruited 33 people, ages 55 to 75, who were randomly assigned to three separate groups. Participants were instructed to play Super Mario 64 for 30 minutes a day, five days a week, take piano lessons (for the first time in their life) with the same frequency and in the same sequence, or not perform any particular task.

The experiment lasted six months and was conducted in the participants' homes, where the consoles and pianos, provided by West's team, were installed.

The researchers evaluated the effects of the experiment at the beginning and at the end of the exercise, six months later, using two different measurements: cognitive performance tests and magnetic resonance imaging (MRI) to measure variations in the volume of gray matter. This enabled them to observe brain activity and any changes in three areas:
    - the dorsolateral prefrontal cortex that controls planning, decision-making and inhibition; - the cerebellum that plays a major role in motor control and balance; and
    - the hippocampus, the centre of spatial and episodic memory.
According to the MRI test results, only the participants in the video-game cohort saw increases in gray matter volume in the hippocampus and cerebellum. Their short-term memory also improved.
The tests also revealed gray matter increases in the dorsolateral prefrontal cortex and cerebellum of the participants who took piano lessons, whereas some degree of atrophy was noted in all three areas of the brain among those in the passive control group.

What mechanism triggers increases in gray matter, especially in the hippocampus, after playing video games? "3-D video games engage the hippocampus into creating a cognitive map, or a mental representation, of the virtual environment that the brain is exploring.," said West. "Several studies suggest stimulation of the hippocampus increases both functional activity and gray matter within this region."

Conversely, when the brain is not learning new things, gray matter atrophies as people age. "The good news is that we can reverse those effects and increase volume by learning something new, and games like Super Mario 64, which activate the hippocampus, seem to hold some potential in that respect," said West. Added Belleville: "These findings can also be used to drive future research on Alzheimer's, since there is a link between the volume of the hippocampus and the risk of developing the disease."

"It remains to be seen," concluded West, "whether it is specifically brain activity associated with spatial memory that affects plasticity, or whether it's simply a matter of learning something new."

Higher physical endurance = better working memory


Mount Sinai researchers have found a positive relationship between the brain network associated with working memory -- the ability to store and process information relevant to the task at hand -- and healthy traits such as higher physical endurance and better cognitive function.

These traits were associated with greater cohesiveness of the working memory brain network while traits indicating suboptimal cardiovascular and metabolic health, and suboptimal health habits including binge drinking and regular smoking, were associated with less cohesive working memory networks.

This is the first study to establish the link between working memory and physical health and lifestyle choices.

The results of the study was e published online in Molecular Psychiatry on Tuesday, December 5.

The research team took brain scans of 823 participants in the Human Connectome Project (HCP), a large brain imaging study funded by the National Institutes of Health, while they performed a task involving working memory, and extracted measures of brain activity and connectivity to create a brain map of working memory.

The team then used a statistical method called sparse canonical correlation to discover the relationships between the working memory brain map and 116 measures of cognitive ability, physical and mental health, personality, and lifestyle choices. They found that cohesiveness in the working memory brain map was positively associated with higher physical endurance and better cognitive function.

Physical traits such as high body mass index, and suboptimal lifestyle choices including binge alcohol drinking and regular smoking, had the opposite association.


"Working memory accounts for individual differences in personal, educational, and professional attainment," said Sophia Frangou, MD, PhD, Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai. "Working memory is also one of the brain functions that is severely affected by physical and mental illnesses. Our study identified factors that can either support or undermine the working memory brain network. Our findings can empower people to make informed choices about how best to promote and preserve brain health."





Air pollution cancels positive health effects of exercise in older adults


Exposure to air pollution on city streets is enough to counter the beneficial health effects of exercise in adults over 60, according to a new study led by scientists at Imperial College London and Duke University.

The findings, published Dec. 5 in The Lancet, show that short-term exposure to traffic exhaust on a busy street can cancel out the positive effects a two-hour stroll would otherwise have on older adults' heart and lungs.

This is the first study to document these negative effects on healthy people as well as those with pre-existing cardiorespiratory conditions such as chronic obstructive pulmonary disease (COPD) or coronary heart disease.

"This adds to the growing body of evidence showing the negative cardiovascular and respiratory impacts of even a short, two-hour exposure to motor traffic pollution," said Junfeng "Jim" Zhang, professor of global and environmental health at Duke. "It highlights the need for stricter air quality limits and better traffic-control measures in our cities."

"Combined with evidence from other recent studies, our findings underscore that we can't really tolerate the levels of air pollution that we currently find on our busy streets," said Fan Chung, professor of respiratory medicine and head of experimental studies medicine at the National Heart & Lung Institute at Imperial College.

Because the research also showed that volunteers who walked for two hours in a large city park -- away from direct exposure to street-side traffic fumes -- experienced significant improvements in lung and vascular functions, "we call for greater access to urban green spaces for people to exercise," Zhang added.

To conduct the study, the researchers recruited 119 volunteers over the age of 60 who were either healthy, had stable COPD, or stable ischemic heart disease. Volunteers walked for two hours midday at one of two London locations: in a relatively quiet part of Hyde Park or along a busy section of Oxford Street, where pollution -- including black carbon, nitrogen dioxide and fine particulate matter from diesel exhaust fumes -- regularly exceeds air quality limits set by the World Health Organization. Physical measurements taken before and after the walks revealed the effects activity had on each volunteer's cardiopulmonary health, including lung capacity, blood pressure, blood flow and arterial stiffness.

Following a stroll in Hyde Park, volunteers' lung capacity improved significantly within the first hour and this improvement lasted for more than 24 hours in many cases. By comparison, a walk along Oxford Street led to a smaller increase during the first hours and no increase later.

Walking in Hyde Park reduced arterial stiffness by more than 24 percent in healthy and COPD volunteers and more than 19 percent in heart disease patients. Walks along Oxford Street yielded much smaller gains. Healthy volunteers experienced a maximum reduction in arterial stiffness of just 4.6 percent; COPD patients saw a 16 percent reduction; and those with heart disease saw an 8.6 percent reduction.

The researchers noted that stress could account for some of the physiological differences seen between the two settings, with the increased noise and activity of Oxford Street having an effect. They also noted that patients with heart disease who took medication to improve their cardiovascular health experienced less severe effects following exposure to the pollution. The medication had a stabilizing effect.


"For many people, such as the elderly or those with chronic disease, the only exercise they very often can do is to walk," Chung said. "Our study suggests that we might advise these people to walk in green spaces, away from built-up areas and pollution from traffic. But for those living in inner cities, this may be difficult to do, and there may be a cost associated with it as they have to travel further away from where they live or work."



Polyunsaturated fatty acids linked to reduced allergy risk


New research from Karolinska Institutet in Sweden reveals that high levels of polyunsaturated fatty acids in children's blood are associated with a reduced risk of asthma or rhinitis at the age of 16 years. The study is published in the Journal of Allergy and Clinical Immunology.

Allergic diseases such as asthma and rhinitis are common and often debut in childhood. Today we know that disease risk is affected by both hereditary and environmental factors.

To date, the present study is the largest to investigate the association between levels of long-chain omega-3 and omega-6 fatty acids in the blood and subsequent development of asthma and other allergic diseases. This study was conducted as part of the Swedish birth cohort BAMSE, and is based on analyses of omega-3 and -6 fatty acids in blood samples from 940 children.

The results show that children who had higher blood levels of long-chain omega-3 fatty acids at the age of 8 years were less likely to have developed asthma or rhinitis by the age of 16 years. High levels of an omega-6 fatty acid called arachidonic acid were associated with a reduced risk of asthma and rhinitis at 16. Among children with asthma or rhinitis at the age of 8 years, higher blood levels of arachidonic acid were associated with a higher probability of being symptom-free at age 16 years.

"Since allergies often debut during childhood it is of particular interest to study if children's environment and lifestyle affect the development of these diseases," says study leader Anna Bergström, researcher at the Institute of Environmental Medicine, Karolinska Institutet.

Polyunsaturated fatty acids are essential to life, and the omega-3 and omega-6 fatty acids that the body is unable to produce itself must be sourced from foods such as nuts and certain vegetable oils; and long-chain omega-3 fatty acids are primarily found in oily fish.

"These new results and those of a previous study we carried out support the current dietary guidelines to eat fish two to three times a week and to vary between oily and lean fish," says Dr Anna Bergström.

Physical activity in mid-life may help protect joint health during aging Wiley

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In an Arthritis Care & Research analysis of 6661 participants in the Australian Longitudinal Study on Women's Health, maintaining at least low levels of physical activity throughout middle age was associated with lower prevalence and incidence of joint symptoms later in life.

The potential protective effect of physical activity on joint symptoms was stronger in obese women than in under or normal weight women, and it was not related to menopausal status or use of hormone therapy.

FDA May Revoke Soy's Heart Health-Claim


The FDA has called into question its health claim finding a link between consumption of soy protein and reduced risk of heart disease. Since 1999, the FDA has allowed manufacturers and advertisers to label soy products with an "authorized" claim of soy's heart-health benefits.  However, proposed rulemaking may reduce it to a "qualified" claim of such benefits, which has a lower scientific standard, or rescind the claim altogether. 

The potential revocation follows numerous studies published since 1999 that present inconsistent findings on the relationship between soy protein and heart disease.

This proposal has been a long time coming. The American Heart Association (AHA) has challenged the FDA's authorization of the health claim as far back as 2008.  The AHA reiterated this position when the FDA announced its decision to review soy's heart-health benefits last month. 

The FDA has opened a 75-day public comment period before it will decide whether to proceed with a final rulemaking stripping soy of its authorized health claim or allowing it to remain.  It would be the first time the FDA has proposed a rule to revoke a health claim.