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Science Square (Issue 107)
Sep 1, 2015

Bratman GN et al. Natural experience reduces rumination and subgenual prefrontal cortex activation. Proceedings of the National Academy of Sciences of the United States of America, June 2015.

More than 50% of the world’s population lives in urban areas, and the number is expected to rise to 70% by 2050. Studies show that urbanization is associated with an increased rate of mental disorders. For example, people living in big cities have a 20% higher risk of anxiety disorders and a 40% higher risk of mood disorders. In addition, people who are born and raised in a large city are twice as likely to develop schizophrenia. There are many possible causes for the correlation between urban life and the susceptibility to mental disorders, but one obvious explanation is that urbanization disconnects humanity from nature; this schism might lead to mental disorders. Scientists tested this hypothesis with a simple experimental design. They split 38 city people, who had no history of mental disorder, into two groups and asked them to walk for 90 minutes. One group walked in a grassland area with trees and shrubs, while the other group walked along a traffic-heavy four-lane roadway. Researchers measured participants’ heart and respiration rates as well as their brain activities through a neuroimaging method called arterial spin labeling (ASL) before and after the walk. Interestingly, researchers did not find a dramatic difference in physiological conditions like heart rates between the groups. However, they found big changes in brain activity, specifically in the subgenual prefrontal cortex, a region of the brain found to be active during ruminative thoughts. Rumination, in psychology, is defined as having repetitive thoughts of negative aspects of the self, such as thinking back over embarrassing or disappointing moments. Researchers found that participants who went on the nature walk showed marked reductions in the activity of the subgenual prefontal cortex, while those who went on the city walk had persistently active subgenual prefrontal cortexes. This suggests that a natural environment somehow reduces rumination. Scientists now aim to figure out what specific factor(s) in nature changes our brain activity. As increased urbanization is almost inevitable, understanding the link between nature and human psychology will help to design better urban plans and to come up with new ways to bring people to nature.

Singh GM et al. Estimated Global, Regional, and National Disease Burdens Related to Sugar-Sweetened Beverage Consumption in 2010. Circulation, June 2015.

According to a new study, sugary drinks alone caused 184,000 deaths worldwide in 2010. Scientists analyzed dietary surveys and large prospective disease studies from 51 countries that included 612,000 people between 1980 and 2010. The consumption of sugar-sweetened sodas and iced teas, sports and energy drinks, and fruit drinks – as well as homemade sugary drinks – were tracked (though 100% fruit juices were excluded from the study). Scientists estimated the contribution of sugary drink consumption to obesity, and of obesity to such diseases as diabetes, cardiovascular disease, and cancers of the breast, colon, esophagus, gall bladder, kidney, pancreas, and ovaries. Then, they calculated how many deaths from those diseases might have been exacerbated by sugary drinks. Analyses showed that sugary drinks caused 133,000 deaths from diabetes, 45,000 from cardiovascular diseases, and 6,450 from cancers. Death percentages linked to sugary drinks varied widely by country: low- and middle-income countries had the highest percentage of deaths. Years of campaigns and education have made most people well aware of the potential risks of high dietary fat. Although there are no health benefits to sugary drinks and they obviously cause many disorders, sugar consumption worldwide is not regulated at all. As alarming as this study was, the death tolls from sugary drinks do not illustrate the adverse effects of such consumption on the health of children. If younger people continue to consume high levels of sugary drinks at the current rate, death and disability from heart disease and diabetes in the future might be even higher than those seen in the current study.

Sobral D et al. Evidence for PopIII-like stellar populations in the most luminous Lyman-a emitters at the epoch of re-ionisation: Spectroscopic confirmation. The Astrophysical Journal, June 2015.

Astronomers recently reported that they have discovered some of the first generation of stars. When these stars exploded, carbon, oxygen, and other elements were generated which would eventually result in modern-day planets and life in the universe. These early stars have been estimated to be thousands of times bigger than the sun and to be composed of only hydrogen, helium, and traces of lithium. They burned for a few million years before they exploded in supernovas that ultimately started new generations of stars with elements like oxygen, carbon, and iron. Groups of astronomers recently captured the signatures of these first generation stars in Cosmos Redshift 7 (CR7), a recently discovered distant galaxy. CR7 is a galaxy from when the universe was about only 800 million years old. Analyses of the spectrum of lights from CR7, which have been traveling to Earth for 12.9 billion years, showed evidence of ionized helium, but not any sign of ionized carbon and oxygen, suggesting that the lights were emitted from the ancient stars. We all want to know where some of our essential elements – like the calcium in our bones or the carbon in our muscles – originally came from, and these recent advances in the field have shown us the beginnings of the elements of life for the first time.