Thursday, October 13, 2016

Why is Myopia on the Rise?

Babies are born with "short" eyeballs, so shortly after birth they are unable to focus on near objects. During early childhood the eyeball elongates until both near and far images are in proper focus. At that point, eyeball elongation generally stops. However, in some people the eyeball continues to elongate beyond its ideal length. The result is the common condition known as myopia, in which the person now sees distant objects as fuzzy and out of focus. Fortunately, the condition is easily corrected with corrective lenses or Lasix surgery.

The incidence of myopia has doubled among young U.S. adults in the past 50 years. No one knows for sure why, though there are some interesting theories. One is that we spend too much time on our computers, cell phones, video games, etc., looking at screens up-close. Another theory is that we don't spend enough time outside in the sunlight. The second theory is supported by research in animals showing that a neurotransmitter called dopamine controls elongation of the eye; too little dopamine throughout childhood and young adulthood allows elongation to continue, leading to myopia. And, as it turns out, dopamine production is stimulated by sunlight.

The theory that the rise in incidence of myopia might be due to too little time in the sun is interesting, but no one is suggesting just yet that spend more time outside. For starters, we don' have any idea just how much time in the sun might be needed to prevent myopia. And we wouldn't necessarily want to trade myopia for skin cancer when myopia is so easily corrected.

Friday, October 7, 2016

Is There a Natural Limit to Human's Lifespan?

For at least a century, human life expectancy (how long a person can expect to live) has been steadily increasing. Some of the increase in life expectancy has been due to advances in medicine and improvements in health care delivery. An increased awareness of safety has also had an effect. And yet, we can all expect to die sometime. Is there a natural upper limit to the human lifespan?

Better understanding of the process whereby cells age and die has led some scientists to propose that the aging process could someday be slowed, to the extent that humans could live a lot longer than they currently do. That may be possible in the distant future. But a new report in Nature seems to suggest that in the absence of successful intervention with the aging process, the "natural" limit to the human lifespan is about 115 years.

The evidence is intriguing. Using the death records of the International Database on Longevity, the authors plotted the age of the oldest person to die in each year from 1968 to 2006. The age of the oldest person to die in any given year rose from 111 years old in 1969 to about to 115 years old in 1995. But since that time it has risen no further. Only three persons have ever lived longer than 115 years (call them exceptions). So unless those scientists who are working on delaying the aging process achieve a breakthrough soon, you better plan on having your affairs in order by the time you reach 115 years old.

Sunday, October 2, 2016

Health Impact of Air Pollution

The World Health Organization (WHO) has just released its latest figures for air pollution worldwide. According to WHO, one specific type of air pollution is associated with over 3 million deaths per year worldwide, not to mention the adverse health effects it produces. It's not ozone or other gaseous pollutants; it's PM 2.5 (particulate matter smaller than 2.5 micrometers in diameter). PM 2.5 is especially damaging to the lungs because it is small enough to be drawn into the deepest parts of the lung's airways. In industrial areas, PM 2.5 includes byproducts of diesel fuel combustion and black carbon, a component of soot. In rural areas and in some cities, naturally-occurring dust is a major contributor.

It might surprise you to learn that the highest levels of air-borne particulate matter worldwide are not necessarily in the most industrialized countries. According to the WHO, the highest levels of PM 2.5 are found in Northern Africa, the middle East, India, and parts of Asia. That's because in many of these areas, naturally-occurring dust is a major problem. In the United States, though, the most significant air pollutants are man-made. Major U.S. cities with the worst air are Chicago and Los Angeles; the states with the worst air are Illinois, Indiana and Ohio, in the industrial heartland. You can use WHO's interactive map to find the reported levels of particulate matter in your specific area. The full WHO report can be viewed here.

Admittedly, we're not likely to make much headway against the problem of naturally-occurring dust anytime soon. Nevertheless, adequate monitoring and reporting can at least warn citizens when their air quality is at its worst, and better education can help them take precautions. Man-made pollution is another matter; in addition to monitoring and education, progress can (and should) be made to reduce its occurrence, to the extent it is feasible to do so.

We can pay now to reduce exposure to bad air or we can pay later in health care costs. It's our choice.

Wednesday, September 28, 2016

Cooler Fabrics

Staying warm indoors is easy; just put on a sweater, sweatshirt, or light jacket. But staying cool under warm conditions indoors has its limits. It's generally not socially acceptable to take off all clothing or even strip down to just a cotton t-shirt in a hot office. But soon there may be a solution. By taking advantage of knowledge of how the human body cools itself, researchers at Stanford University believe that they have developed a clothing fabric that can keep the wearer significantly cooler than other fabrics such as cotton. Their findings are documented in the Sept. 2 issue of Science and explained in layperson's terms in Forbes Magazine.

Except when a person is sweating, the body loses most of its heat as radiant heat energy in the infrared part of the wavelength spectrum. (You can't see infrared radiation because its wavelength is longer than visible light.) The problem is that fabrics such as cotton reflect most of this radiant heat back toward the body; that's partly how they keep the body warm. Understanding this, the researchers started with sheets of opaque polyethylene that allow 90% of IR radiation to pass through (cotton only transmits 5%.) Then they punctured it with tiny needles to allow air to pass through and added a substance that allows the fabric to wick moisture away. Finally, to make the material feel more like traditional fabrics they bonded two sheets of the material to a middle layer of widely spaced cotton mesh.

Then they tested the new fabric. In a room kept at 23.5oC the temperature of bare skin was 33.5oC, skin covered with cotton was 37oC, and skin covered with the new fabric was 35oC. That's fully 2oC lower than cotton, giving the new fabric an advantage in a warm room.

There's no guarantee that the new fabric will catch on with clothing designers. But at least it introduces a new way of thinking about how to create new fabrics for specific purposes, based on human physiology.

Thursday, September 22, 2016

Wearable Activity Monitors and Weight Loss

It may be fun to record how many steps you took today. But does wearing an activity monitor help a person to lose weight?

To find out, researchers at The University of Pittsburgh enlisted nearly 500 people in a randomized trial. For six months, all participants were asked to adhere to a low-calorie diet and to exercise in prescribed ways. After six months the diet and exercise recommendations were continued for another year and a half, but now half of the participants wore an activity monitor and the other half (the control group) did not.

The researchers had hypothesized that those wearing the activity monitors would lose more weight than those in the control group. Surprisingly, that was not the case. In fact, the activity monitor-wearers lost slightly less weight; only 7.7 lb versus 13.0 lb. in the control group.

So what are we to make of this? Not much, except that human beings and their behaviors are, well, complicated. Perhaps wearing an activity monitor reduces diet compliance (self-reported in this study). Or perhaps an activity monitor gives the wearer an inflated perception of how hard they actually are exercising, so that they aren't expending as many calories as they think (physical activity, too, was self-reported). Who knows? For now, all we know is that wearing an activity monitor doesn't help one lose weight.

Tuesday, September 20, 2016

Purposefully Causing the Extinction of a Species

Question: If it were technically possible, should we deliberately cause the extinction of species that we perceive as harmful (to us)? If we could actually eliminate forever the species of mosquitoes that carry certain human diseases such as yellow fever, malaria, and the Zika virus, should we do it?

Think hard on this question, because one day it may be possible. Right now, we know how to modify mosquitoes so that the males are sterile; when these sterile males are released into the wild there is a sharp drop in the mosquito population in the local region, but not a complete extinction because there are still plenty of wild normal males to ensure the survival of the species. But what if you could modify mosquito genes so that they could only produce male offspring? Such a change would wipe out the entire species in short order.

The ides of deliberately causing the extinction of certain species may be morally repugnant to some. But even if its not, we need to be aware of that there may be risks. Time and time again we've seen how the introduction of an invasive species disrupts an ecosystem. What might be the unintended consequence of the opposite scenario; eliminating a species from its ecosystem? If we were to eliminate a species in the wild, it might be wise to keep colonies of the species in captivity so that they could be re-introduced if necessary.

On the political front, who would be responsible for giving consent for a species extinction? Mosquitoes know no political boundaries. Any plan to eliminate a species, even one so universally unloved as a mosquito, should require nearly universal international approval. Don't count on that any time soon.

Wednesday, September 14, 2016

The Presidential Candidates' Plans to Reduce Drug Prices

What are Hillary Clinton's and Donald Trump's views on the skyrocketing costs of prescription drugs in the U.S.? Who, exactly, is to blame for the rising costs, and what could be done about it? There's an article in The Lancet (a British medical journal) last month on the subject. Some of Donald Trump's ideas are not well fleshed out, as is usual for Donald Trump: you just have to trust him. Hillary Clinton, also true to form, focuses her attention on specific changes that she has in mind.

After reading the article I was left with a lot of unanswered questions. For example, why is it that although the U.S. develops most of the drugs, we end up paying more for them than people in other countries? Should drug companies really get tax deductions for their marketing expenses? Why isn't Medicare allowed to negotiate drug prices directly with pharmaceutical companies, as insurance companies and pharmacy benefit management companies do?

There has been a lot of news coverage lately about Mylan Pharmaceuticals' epinephrine injection device called the EpiPen, which contains about a dollar's worth of epinephrine but sells for about $300. It's time to ask whether this is really reasonable.