Thursday, October 27, 2016

Optimal walking and cycling speeds to reduce air pollution inhalation

Cyclists should be riding at speeds between 12 and 20 kilometres per hour (7-12 mph) on city roads, while pedestrians should be moving at two to six kilometres per hour (1.2-3.6 mph) to minimize their inhalation of air pollution while still getting the health benefits of exercise, according to new UBC research.

"The faster you move, the harder you breathe and the more pollution you could potentially inhale, but you also are exposed to traffic for a shorter period of time. This analysis shows where the sweet spot is," said Alex Bigazzi, a UBC transportation expert in the department of civil engineering and school of community and regional planning who conducted this analysis.

Using a U.S. Census-based computer model of 10,000 people, Bigazzi calculated ideal travel speeds that he calls the minimum-dose speeds (MDS) for different age and sex groups. For female cyclists under 20, the ideal speed linked to the least pollution risk is 12.5 kilometres per hour on average on a flat road. For male cyclists in the same age group, it's 13.3 kilometres per hour. Ideal travel speeds were at 13 and 15 kilometres per hour for female and male cyclists in the 20-60 age group.

Female and male pedestrians under 20 years old should be walking at speeds around three kilometres per hour, while their older counterparts should look at reaching at least four kilometres per hour, to breathe in the least amount of pollution over a trip. Bigazzi also computed these ideal travel speeds for other road grades.

"If you move at much faster speeds than the MDS--say, cycling around 10 kilometres faster than the optimal range--your inhalation of air pollution is significantly higher," said Bigazzi. "The good news is, the MDS numbers align pretty closely with how fast most people actually travel."

The findings, which build on Bigazzi's recent research on the high amounts of toxic chemicals absorbed by cyclists on busy city streets, are described in a paper published recently in the International Journal of Sustainable Transportation.

Vitamin D can reduce asthma attacks

A recent Cochrane Review has found evidence from randomised trials, that taking an oral vitamin D supplement in addition to standard asthma medication is likely to reduce severe asthma attacks.

Asthma is a common chronic disease affecting about 300 million people worldwide. The symptoms of asthma include wheezing, coughing, chest tightness and shortness of breath.

Low blood levels of vitamin D have been linked to increased risk of asthma attacks in children and adults with asthma. There has been a growing interest in the potential role of vitamin D in asthma management because it might help to reduce upper respiratory infections, (such as the common cold) that can lead to exacerbations of asthma. Several clinical trials have tested whether taking vitamin D as a supplement has an effect on asthma attacks, symptoms and lung function in children and adults with asthma.

The team of Cochrane researchers found seven trials involving 435 children and two studies, involving 658 adults. The study participants were ethnically diverse, reflecting the broad range of global geographic settings, involving Canada, India, Japan, Poland, the UK, and the U.S. The majority of people recruited to the studies had mild to moderate asthma, and a minority had severe asthma. Most people continued to take their usual asthma medication while participating in the studies. The studies lasted for between six and 12 months

The researchers found that giving an oral vitamin D supplement reduced the risk of severe asthma attacks requiring hospital admission or emergency department attendance from 6% to around 3%.They also found that vitamin D supplementation reduced the rate of asthma attacks needing treatment with steroid tablets. These results are based largely on trials in adults. They also found that vitamin D did not improve lung function or day-to-day asthma symptoms, and that it did not increase the risk of side effects at the doses that were tested.

The Cochrane Review's lead author, Professor Adrian Martineau from the Asthma UK Centre for Applied Research, Queen Mary University of London, said, "We found that taking a vitamin D supplement in addition to standard asthma treatment significantly reduced the risk of severe asthma attached, without causing side effects."

He added, "This is an exciting result, but some caution is warranted. First, the findings relating to severe asthma attacks come from just three trials: most of the patients enrolled in these studies were adults with mild or moderate asthma. Further vitamin D trials in children and in adults with severe asthma are needed to find out whether these patient groups will also benefit. Second, it is not yet clear whether vitamin D supplements can reduce risk of severe asthma attacks in all patients, or whether this effect is just seen in those who have low vitamin D levels to start with. Further analyses to investigate this questions are on-going, and results should be available in the next few months."

Exercise is an excellent preventive and curative treatment for many diseases

Researchers, it is hoped, will one day find a miracle cure for all kinds of diseases. Yet over and over again it has been shown that even if it takes a little more effort than swallowing a little pill, exercise is an excellent preventive and curative treatment for many diseases. A new study, whose preliminary results will be presented today at the Canadian Cardiovascular Congress and soon be published in the Journal of Cardiopulmonary Rehabilitation and Prevention, also supports this finding. The study shows that even low physical fitness, up to 20% below the average for healthy people, is sufficient to produce a preventive effect on most of the risk factors that affect people with cardiovascular disease.

"This is great news for people with heart disease who have difficulty adhering to a regular -- mainly aerobic -- exercise program," said Daniel Curnier, a professor at the University of Montreal's Department of Kinesiology, who led the study. "Small improvements in their fitness level are enough. You don't have to be an great athlete to benefit from these effects."

"We know from many studies that good physical fitness reduces cardiovascular mortality, and that physical activity has a positive impact on cardiovascular risk factors following a rehab program," said Maxime Caru, a doctoral student in human kinetics at UdeM and lead author of the study. "However, the impact of physical fitness level on risk factors has remained an open question. That is why our research team asked the following question: "Is good physical condition required to produce a preventive effect on these cardiovascular risk factors?"

Pedalling with heart

Changes in society, marked by industrialization, have had a significant impact on the physical activity of humans, who have become increasingly sedentary over the years. The increase in risk factors, including abdominal circumference, depression, diabetes, dyslipidemia, hypertension, obesity, excess weight, and smoking -- along with physical inactivity -- provides the perfect storm for developing heart disease, which is one of the leading causes of death in the world, representing 31% of global mortality. And it has continued to grow in recent years.

"It is common to meet people entering a cardiac rehab centre who are totally out of shape and whose exercise is irregular or non-existent, which has a harmful effect on general and cardiovascular health," said Caru, who is also a doctoral student in psychology at the University of Paris-Nanterre.

To measure the impact of physical fitness on heart disease risk factors, the researchers selected 205 men and 44 women with heart disease, including coronary artery disease, stroke, congestive heart failure, and heart valve disease, and had them undergo a cycle ergometer (stationary bike) stress test to determine their fitness level.

The results showed that normal physical fitness, even up to 20% below the population average, is sufficient to have a preventive effect on five of the eight risk factors affecting people with cardiovascular disease -- abdominal circumference, diabetes, hypertension, obesity, and excess weight. Normal physical fitness means having the physical fitness of a person of the same weight, height, sex, and age, and who is disease-free. The easiest way to achieve this is to follow the recommendations of the World Health Organization -- 150 minutes per week of moderate exercise or 75 minutes of vigorous exercise.

Depression: higher standards

Depression is a significant risk factor for cardiovascular disease because cardiac patients who have experienced a depressive episode have recurring heart problems. The results of the study have demonstrated the importance of a good fitness level, before and after a heart attack, to produce the preventive effect on depression.

The study sheds new light on the overall role of physical fitness in the development of cardiovascular risk factors in patients with cardiovascular disease. However, the researchers stress the importance for cardiac patients to consult their doctor before embarking on an exercise program and to consult a kinesiologist: "Only these professionals are able to know which type of exercise is safe for your condition and how to implement an exercise program," warn the authors.

About the study

Maxime Caru and Daniel Curnier presented "Preventive fraction of physical fitness on risk factors in cardiac patients" at the Canadian Cardiovascular Congress on October 21, 2016. The scientific article, signed by Maxime Caru, Laurence Kern, Marc Bousquet, and Daniel Curnier will soon be published in the Journal of Cardiopulmonary Rehabilitation and Prevention.

Tuesday, October 25, 2016

New guideline on calcium and vitamin D supplementation

A new evidence-based clinical guideline from the National Osteoporosis Foundation (NOF) and the American Society for Preventive Cardiology (ASPC) says that calcium with or without vitamin D intake from food or supplements that does not exceed the tolerable upper level of intake (2,000 to 2,500 mg/d) should be considered safe from a cardiovascular standpoint. Obtaining calcium from food sources is preferred, but supplements can be used to address dietary shortfalls. The guideline is published in Annals of Internal Medicine.

Calcium supplements have been recommended for persons who do not consume adequate calcium from their diet as a standard strategy for preventing osteoporosis-related fractures. Conflicting reports have suggested that calcium intake, particularly from supplements, may have either beneficial or harmful effects on cardiovascular outcomes. To update the evidence on calcium and vitamin D, investigators from the Tufts University School of Medicine reviewed randomized trials and prospective cohort studies published since their last evidence report in 2009. Their findings were used to inform the joint clinical guideline from NOF and ASPC.

A total of 31 studies were included in the review. Of the four randomized trials reviewed, none found a statistically significant difference in risk for cardiovascular events or mortality between groups receiving supplements of calcium alone or calcium plus vitamin D compared to those receiving placebo. None of the 27 cohort studies included in the review conclusively linked total, dietary, or supplemental calcium intake levels to cardiovascular disease and cerebrovascular disease, mortality, or all-cause mortality. Because excessive calcium intake is nearly impossible to achieve via diet, safety of supplementation had been an area of concern. Of the three supplementation-specific trials included in the review, none found a statistically significant effect of calcium supplementation on cardiovascular disease outcomes. Based on this moderate-quality evidence, the review team concluded that calcium intake from food or supplement sources at levels within the recommended tolerable range should be considered safe for generally healthy adults.

Increasing muscle strength can improve brain function

Increased muscle strength leads to improved brain function in adults with Mild Cognitive Impairment (MCI), new results from a recent trial led by the University of Sydney has revealed.

With 135 million people forecast to suffer from dementia in 2050, the study's findings--published in the Journal of American Geriatrics today--have implications for the type and intensity of exercise that is recommended for our growing ageing population.

Mild Cognitive Impairment defines people who have noticeably reduced cognitive abilities such as reduced memory but are still able to live independently, and is a precursor to Alzheimer's disease.

Findings from the Study of Mental and Resistance Training (SMART) trial show, for the first time, a positive causal link between muscle adaptations to progressive resistance training and the functioning of the brain among those over 55 with MCI.

The trial was conducted in collaboration with the Centre for Healthy Brain Ageing (CHeBA) at University of New South Wales and the University of Adelaide.

"What we found in this follow up study is that the improvement in cognition function was related to their muscle strength gains" said lead author Dr Yorgi Mavros, from the Faculty of Health Sciences, at University of Sydney.

"The stronger people became, the greater the benefit for their brain."

SMART was a randomised, double-blind trial involving 100 community-dwelling adults with MCI, aged between 55 and 86. They were divided into four groups doing either:Resistance exercise and computerised cognitive training;
  • Resistance exercise and a placebo computerised training (watching nature videos);
  • Brain training and a placebo exercise program (seated stretching/calisthenics); or
  • Placebo physical exercise and placebo cognitive training.
Participants doing resistance exercise prescribed weight lifting sessions twice week for six months, working to at least 80 per cent of their peak strength. As they got stronger, the amount of weight they lifted on each machine was increased to maintain the intensity at 80 per cent of their peak strength.

The primary outcomes of a paper published in 2014 found these participants' global cognition improved significantly after the resistance training, as measured by tests including the Alzheimer's disease Assessment Scale-Cognitive scale. The cognitive training and placebo activities did not have this benefit. The benefits persisted even 12 months after the supervised exercise sessions ended.

"The more we can get people doing resistance training like weight lifting, the more likely we are to have a healthier ageing population," said Dr Mavros.

"The key however is to make sure you are doing it frequently, at least twice a week, and at a high intensity so that you are maximising your strength gains. This will give you the maximum benefit for your brain."

These new findings reinforce research from the SMART trial published earlier this year, whereby MRI scans showed an increase in the size of specific areas of the brain among those who took part in the weight training program. These brain changes were linked to the cognitive improvements after weight lifting.

"The next step now is to determine if the increases in muscle strength are also related to increases in brain size that we saw," said senior author Professor Maria Fiatarone Singh, geriatrician at University of Sydney.

"In addition, we want to find the underlying messenger that links muscle strength, brain growth, and cognitive performance, and determine the optimal way to prescribe exercise to maximise these effects."

Long-term exposure to air pollution linked to high blood pressure

Long-term exposure to air pollution is linked to a greater incidence of high blood pressure, according to the largest study to investigate the effects of both air pollution and traffic noise by following over 41,000 people in five different countries for five to nine years.

The study, which is published today (Tuesday) in the European Heart Journal [1], found that among adults, up to one extra person per 100 people of the same age group living in the most polluted areas of cities would develop high blood pressure (hypertension) compared to those living in the less polluted areas. This risk is similar to the effect of being overweight with a body mass index (BMI) between 25-30 compared to people with normal weight (BMI 18.5-25). High blood pressure is the most important risk factor for premature illness and death.

This study is one of the first to investigate both air pollution and traffic noise simultaneously and it found that traffic noise is associated with an increase in cases of hypertension as well. The way the study was conducted enabled the researchers to estimate the risk that was linked to air pollution and the risk linked to noise separately. The association of air pollution with hypertension remained even when exposure to traffic noise was considered in the analysis. The researchers say this is an important finding because there are differing ways of reducing air pollution and noise.

A total of 41,072 people living in Norway, Sweden, Denmark, Germany and Spain participated in the study, which was part of the "European Study of Cohorts for Air Pollution Effects" (ESCAPE) project that is investigating long-term effects of exposure to air pollution on human health in Europe. Information on blood pressure was gathered when the participants joined the study and during a follow-up examination in later years. None had hypertension when they joined the study, but during the follow-up period 6,207 people (15%) reported that they developed hypertension or started to take blood pressure-lowering medications.

Between 2008 and 2011, the researchers measured air pollution during three separate two-week periods (to allow for seasonal effects). They used filters to capture information on concentrations of polluting particles known as "particulate matter" (PM) of different sizes: PM10 (particles less than or equal to 10 microns [2] in diameter), PM2.5 (less than or equal to 2.5 microns), PMcoarse (PM10 minus PM2.5) and PM2.5 absorbance (a measurement of soot particles). These measurements were taken at 20 sites in each of the areas being studied, and measurements of nitrogen oxides were measured at 40 different sites in each area. Traffic density was assessed outside the homes of the participants and traffic noise was modelled according to the EU Directive on environmental noise.

The researchers found that for every five micrograms [3] per cubic metre (5 μg/m3) of PM2.5, the risk of hypertension increased by a fifth (22%) in people living in the most polluted areas compared to those in the least polluted areas. Higher soot concentrations also increased the risk.

For exposure to chronic traffic noise, the researchers found that people living in noisy streets, where there were average night time noise levels of 50 decibels, had a six percent increased risk of developing hypertension compared to those living on quieter streets where average noise levels were 40 decibels during the night.

Professor Barbara Hoffmann, Professor of Environmental Epidemiology at the Centre for Health and Society at Heinrich-Heine-University of Düsseldorf, Germany, who led the analysis, said: "Our findings show that long-term exposure to particulate air pollution is associated with a higher incidence of self-reported hypertension and with intake of anti-hypertensive medication. As virtually everybody is exposed to air pollution for all of their lives, this leads to a high number of hypertension cases, posing a great burden on the individual and on society.

"Exposure to traffic noise shares many of the same sources with air pollution and so has the potential to confound the estimates of the adverse effects of pollution on human health. However, this study controlled for traffic noise exposure and found that the associations of air pollution with hypertension did not vanish. This is important because preventive measures for air pollution and noise differ.

"One very important aspect is that these associations can be seen in people living well below current European air pollution standards. This means, the current legislation does not protect the European population adequately from adverse effects of air pollution. Given the ubiquitous presence of air pollution and the importance of hypertension as the most important risk factor for cardiovascular disease, these results have important public health consequences and call for more stringent air quality regulations."

The study found there were higher average levels of pollution in the central and southern European study areas - Germany and Spain - than in the Scandinavian areas - Norway, Sweden and Denmark. Exposure to traffic noise and traffic load was highest in the study areas of Sweden and Spain.

The researchers say that it is possible that air pollution and noise affect different, or not completely overlapping, pathways involved in disturbances in the way the body normally functions. Possible biological mechanisms for the adverse effect of air pollution on the functioning of the heart and blood vessels include local and systemic inflammation, oxidative stress (a build-up of damaging molecules in the body), and an imbalance in correct functioning of the nervous system. Noise is thought to affect the functioning of both the nervous and hormonal systems.

Cut dietary omega 6 and boost omega 3 to curb soaring obesity rates

Governments and international bodies should ditch their obsession with calories and energy expenditure to curb soaring obesity rates, and instead focus on restoring the correct balance of omega 6 and omega 3 fatty acids in the food supply chain and diet, urge experts in an editorial in the online journal Open Heart.

Nutrition policies based purely on the mismatch between 'calories in and energy out' in the belief that all calories are equal, have "failed miserably over the past 30 years," argue Drs Artemis Simopoulos of the Center for Genetics, Nutrition, and Health, Washington DC, and James DiNicolantonio of Saint Luke's Mid America Heart Institute, Kansas.

So much so, that 1.5 billion people around the globe are now overweight while 500 million are obese.

Major changes in food supply over the past century, as a result of technological advances and modern farming methods, have distorted the omega 6 to omega 3 fatty acid ratio in the typical Western diet, which developing countries are now also increasingly adopting, say the authors.

The production of vegetable oils high in omega 6, such as sunflower, safflower, and corn oils, has soared, while animal feeds have switched from grass, which contains omega 3, to grain, resulting in higher levels of omega 6 in meat, eggs, and dairy products.

This matters because while the body needs both types of fatty acid, human beings evolved to eat a diet containing equal amounts of omega 6 and omega 3 in it. But that dietary ratio is now a belt-busting 16:1 rather than the healthy 1: 2/1, the authors contend.

Fatty acids act directly on the central nervous system, influencing food intake and the sensitivity of the hormones involved in blood sugar control (insulin) and appetite suppression (leptin).

But too much omega 6 promotes inflammation and is prothrombotic (increasing the risk of blood clotting) as well as boosting production of white fat tissue that is stored rather than 'good' energy-burning brown fat tissue.

And copious amounts of white fat and chronic inflammation are the hallmarks of obesity, the authors point out, as well as being linked to type 2 diabetes, cardiovascular disease, metabolic syndrome, and cancer.

Furthermore, different populations metabolise fatty acids differently, making them more or less vulnerable to the consequences of an imbalance, they add.

They point to several key studies that have shown a strong link between the dietary omega 6 to omega 3 ratio and long term weight gain.

"The time has come to return the omega 3 fatty acids in the food supply and decrease the omega 6 fatty acids by changing the cooking oils and eating less meat and more fish," they write. "The composition of the food supply must also change to be consistent with the evolutionary aspects of diet and the genetics of the population," they add.

"The scientific evidence to balance the omega 6 to omega 3 ratio is robust and necessary for normal growth and development, prevention and treatment of obesity and its comorbidities, including diabetes, cardiovascular disease and cancer," they continue.

And they conclude: "It is the responsibility of governments and international organisations to establish nutrition policies based on science and not continue along the same path of focusing exclusively on calories and energy expenditure, which have failed miserably over the past 30 years."