Obesity Rates Over Time

Obesity has reached epidemic proportions in the United States. These increased body fat reserves are associated with an increased risk of numerous health problems, including coronary heart disease and heart attacks, diabetes mellitus, stroke, some cancers, and more. Obesity has become so prevalent in the U.S. today that it is difficult to remember that just a couple decades ago, the average American was not overweight, and few were obese. Below is a link to an animated graphic showing the remarkable increase in obesity in U.S. states over time. In the ideal case, the entire map would be colored the aqua color, since there would be data from every state but no obese people.

This is the first frame. See animated version.

As is commonly done, obesity is defined here based on the body-mass index (BMI). The BMI is calculated by dividing one’s weight by one’s height squared. It is traditionally given in SI units (that is, kg/m²), so if U.S. customary units are used, they must be converted. BMIs in the range from 18.5–25 kg/m² is considered normal or healthy. 25–30 kg/m² is overweight, and greater than or equal to 30 kg/m² is obese. (40 kg/m² or greater is often considered morbidly obese, or sometimes 35 kg/m² or greater along with other risk factors is included.) The use of BMI is imperfect (for instance, a very muscular person will have a high weight and therefore BMI), but in practice it is usually simple to differentiate obese from muscular people.

For instance, consider a 1.78-m (5 ft., 10 in.) tall person. The healthy range would be from 58.5–79.0 kg (129–174 lb.). Those weighing more than this would be overweight, and over 94.8 kg (209 lb.) would be obese. For a 1.63-m (5 ft., 4 in.) tall person, the healthy range would be from 47.4–64.0 kg (104–141 lb.). Greater than 76.8 kg (169 lb.) would be obese.

It’s easy to calculate your own BMI. There are plenty of BMI calculators and BMI charts on the Internet. But the fastest way is probably to use Google Calculator: just type your calculation directly into the main search box (see example).

The obesity data are taken from the CDC. I reformulated them into an animated GIF since I didn’t care for the original color scheme and also because that presentation isn’t easily exported to other sites. You are free to use the image (direct linking is fine), though I would appreciate a link back here if you do.

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Minnesota Is Now Smoke-Free

Today, 1 October 2007, a state-wide smoking ban took effect in my state. A major success for public health and especially employees’ health, this law puts major restrictions on indoor smoking in public places with relatively few loopholes. Bars, restaurants, and almost all other indoor locations are included. Private residences, hotel and motel rooms, cigar shops, and casinos and other establishments on Native American lands are exempt. As is well-known, there is an enormous body of scientific data indicating the harm smoking causes to bystanders. Those who work in establishments where smoking is permitted are especially at risk. As attention to public health mounts, smoking bans cover more and more of the United States—at the city, county, and state levels. According to Wikipedia, over half of Americans are covered by some sort of smoking ban.

Wikipedia also featured this interesting map of the United States, showing active and scheduled smoking bans. It uses an innovative “additive color key” to designate the type of ban.

State-wide smoking bans. Credit: Mike Schiraldi.

The gray states have no state-wide smoking bans. The red states, Idaho and Georgia, ban smoking in restaurants; the green ones (North and South Dakota) ban smoking in non-hospitality workplaces (that is, not restaurants or bars); and the yellow states (Nevada, Arkansas, Louisiana, Tennessee, and Florida) ban smoking in both. The lavender state (New Hampshire) bans smoking in bars and restaurants. The white states ban smoking in all three: bars, restaurants, and non-hospitality workplaces.

Energy and Health: Spotlight on the Lancet‘s Series Covering Climate Change and More

As a human and a resident of planet Earth, I care about my home and the environment, and for the other life that shares it with me. But as a physician, I have a special interest in examining the relationship between the health of our planet and that of human health; I have a strong desire to promote public health. And therefore I am indebted to Inel for bringing my attention (via a comment and a subsequent blog entry) to a wonderfully important series of articles in the Lancet covering the many-faceted relationship between energy and health. At the least, I feel that all physicians are obligated to read this series.

The Lancet is one of the world’s premiere medical journals (along with the New England Journal of Medicine, the Journal of the American Medical Association, and the British Medical Journal). In publishing this series, they are taking on a large, complex issue with significant public health implications that previously have not drawn much attention. Strategies to help ameliorate the problem are well–thought out. The series covers so much detail I’d like to devote a series of my own posts to discuss and analyze them.

Editor-in-chief Richard Horton writes the introductory comment, entitled “Righting the Balance: Energy for Health”:

The current debate about the impact of human beings on our planet—especially with respect to climate change—is one of the most important issues of our time. But that debate is presently unbalanced and too narrow. It neglects a far larger set of issues focused on energy—and health.

Energy is a critical, yet hugely neglected, determinant of human health. Health is an important enough aspect of energy policy to deserve a much greater influence on decisions about our future personal, national, and global energy strategies. Society suffers from a disordered global energy metabolism. Energy is as important as any vaccine or medicine. 2 billion people currently lack access to clean energy: they live in energy poverty and insecurity. International institutions, such as the World Bank and WHO, have repeatedly failed to make the connection between energy and health in their country work.

(continued — free registration required)

Dr. Horton gives examples of changes that we need to make at these three levels, such as changing travel habits at the personal level, designing new urban infrastructure at the national level, and controlling greenhouse gases at the global level. This introduction sets the stage for the in-depth analysis to follow.

While physicians should certainly read these, I also encourage others in the allied health professions as well as anyone with an interest in public health to read them as well. They are written in clear language and do not rely on advanced medical terminology or concepts. I will update this post with links to additional posts on the individual articles as I write them.

Source: Horton, R. “Righting the balance: energy for health”. The Lancet 2007;370:921. DOI:10.1016/S0140-6736(07)61258-6. Full text available; free registration required.

Motorized Wheelchair Guided by Thoughts

A company called Ambient is developing a new wheelchair that is controlled by words the user thinks of. The system, called Audeo, uses a neckband to pick up signals in the nerves that control the larynx, or voice box. Obviously, this requires that the operator still has control of those nerves, though he doesn’t have to have control of the other muscles or the coordination that is required for speech. This has the potential to restore some mobility to those who have very little strength or coordination to make purposeful movements. And as this technology is refined, the potential uses are many: users could control other devices, such as a computer or television. If the “vocabulary” of the system is increased, the system could also function as an artificial speech synthesizer that could sense the words the user was trying to say and construct them directly. See New Scientist for more.

Below is a video demonstrating the system.

Growing Body Parts

There has been some exciting work regarding the growing or re-growing of human body parts.

Some animals have an incredible ability to regenerate missing body parts—a classic example being some species of starfish. However, for the most part, it is not possible to regrow complex organs. In humans, damaged tissue usually is replaced by “generic” scar tissue, if it all. There are several reasons why humans cannot regenerate most body parts. For one, once cells become specialized, they often lost the ability to divide. Another reason is that arms and hearts and so on develop according to a specific pattern during embryonic development in the womb; there is no “program” for starting with part of a fully-developed structure and regrowing the rest. And furthermore, there is some evidence that the ability to regenerate has been sacrificed to avoid cancer. Cancer is essentially uncontrolled cell growth; many checkpoints that help regulate this may also prevent stem cells from recreating damaged tissue. Presumably, this balance reflects an optimum balance for the survival of our ancestors.

But scientists are working to augment this ability. As New Scientist reports, researchers in Japan were able to grow tooth buds in the laboratory, then transplant them to the jaws of mice where they developed into normal teeth; they even developed a blood supply. Also reported in New Scientist is the efforts of American researchers to grow new ligaments in the laboratory. Ligament injuries are quite common, and they tend to heal quite poorly.

Finally, LiveScience discusses regrowth of human fingertips after accidents, and mentions a few notable cases.

Retinal Implant Helps Restore Vision

The major components of the new prosthesis. The small wearable computer is not included. Credit: Mark Humayun/AAAS. Source: New Scientist.

An article by Gaia Vince in New Scientist reports on a retinal prosthesis designed to help restore vision to blind people. After a prototype was successfully used in six people, further trials are set to begin. While cochlear implants are used to give deaf people some ability to hear, there has been no comparable, practical system for those who cannot see.

The system has several components. The user wears a pair of glasses with a built-in camera. The information is then transmitted to a wireless computer around the size of a mobile telephone that the user must keep with him. This computer processes the data, then transmits it to a receiver implanted in the user’s head. This is connected to a chip on the user’s retina. This all occurs extremely quickly, as discrepancy between perceived movement and visual changes would cause nausea and dizziness.

The device is still preliminary; the resolution is quite limited, naturally. But it is interesting that the brains of the patients seem to adapt to the limited visual input, and their vision improved over time. The article notes one patient’s observation:

At the beginning, it was like seeing assembled dots — “now it’s much more than that,” says Terry Bryant, aged 58, who received the implant in 2002 after 13 years of blindness. “I can go into any room and see the light coming in through the window. When I am walking along the street I can avoid low hanging branches and I can cross a busy street.”

Similar to the cochlear implant, an intact nervous system is required. This prothesis links with the ganglion cells at the back of the eye and the signals travel over the optic nerve to the brain. Damage to any of these components—such as damage to the ganglion cells, injury to the optic nerve, or stroke—will result in blindness that this prosthesis cannot correct. For that, we’ll have to wait for new technology.

Giant Microbes

Stuffed “animal” version of E. coli, from GIANTmicrobes.

My sister sent me a link to GIANTmicrobes, a web site that sells stuffed “animal” versions of many common microbes and more. There’s quite a variety there—aside from the bacterium E. coli, featured here, they have viruses, insects, protozoans, and even prions! (That’s my favorite.)

I think anyone in the health sciences would appreciate these. Most range in price from US $6–7.

Virtual Touch

There was an interesting article in New Scientist today about research towards developing a “haptic” glove. This glove would simulate tactile information, analagous to the way a television screen simulates visual information or speakers simulate auditory information. However, simulating touch is much more difficult for several reasons.

One of the main ways we determine the texture of something is through vibration. As we run our fingers over it, different textures have different patterns of high and low points, and vibration sensors in our fingertips are stimulated differently. Touch is complex, though, since we may also pick up and manipulate an object. As Tom Simonite writes in New Scientist,

“Virtual fabric” that feels just like the real thing is being developed by a group of European researchers. Detailed models of the way fabrics behave are combined with new touch stimulating hardware to realistically simulate a texture’s physical properties.

Detailed measurements of a fabric’s stress, strain and deformation properties are fed into a computer, recreating it virtually. Two new physical interfaces then allow users to interact with these virtual fabrics – an exoskeleton glove with a powered mechanical control system attached to the back and an array of moving pins under each finger. The “haptic” glove exerts a force on the wearer’s fingers to provide the sensation of manipulating the fabric, while the “touching” pins convey a tactile sense of the material’s texture.

(continue reading at New Scientist)

Of course, the benefits to virtual reality games are obvious. But there are many possible medical and industrial applications as well, such as manipulation of toxic substances or work in dangerous environments, or perhaps remote or robotic surgery.

There does not seem to be any olfactory or gustatory simulation on the horizon, though.

Memory Chip

Scientific American has a neat piece of news in its February 2007 issue (“Chipping In” by Anna Griffin; subscription required for full text). For some time, we have had technology that can pick up signals from neurons (brain and nerve cells), for instance, allowing paralyzed patients rudimentary control over a computer or prosthesis.

But a team at the University of Southern California, led by Theodore W. Berger, have taken this a step further. For twenty years he and his team studied the brains of rats; specifically, how neurons communicate in the hippocampus, a region of the brain involved in memory. They developed a model of how the neurons responded to various inputs and built it into a chip. They then took slices of hippocampal tissue, removed part of it, and replaced it with the chip, “[restoring] function by processing incoming neural signals into appropriate output with 90 percent accuracy,” according to the Scientific American article.

I find this to be very exciting. This sort of research could one day lead to devices to help humans with brain damage or memory problems, for instance, though of course that is still far away. Even at this stage, it took some interesting engineering work to figure out how to make a silicon chip interact with brain tissue. The next step will be to design a chip to work with a living brain, instead of tissue slices.

But what really fascinates me is that they were able to model the function of that brain tissue mathematically, to calculate how the section of neurons would respond to various inputs. This brings us closer to understanding just how brain functions such as memory and consciousness arise from the biology and chemistry of the brain.

It does suggest some future ethical and philosophical puzzles, though. Will we eventually be able to reproduce the functioning of the entire rat brain? How about that of a human? Might we one day be able to calculate the functioning of a human mind, to reproduce a mind as software?

My brain looks forward to future advances.

Prosthetic arm

New Scientist reports about an article in this week’s Lancet. Prosthetic limbs are getting quite advanced! The article discusses a prosthetic arm that has been attached to a 26-year-old woman. Motor (movement) nerves have been attached in a way to allow for more intuitive control of the limb. She is able to achieve remarkable control and accomplish activities of daily living such as cooking and dressing, albeit a bit more slowly. Below is a video of this remarkable woman demonstrating use of her new arm.

Take a look at the advantage this prosthesis offers over previous ones.

They also attached the sensory nerves to her chest so that if she is touched there, she feels the sensation as if it is coming from her arm. The next step will be to develop a sensory mechanism for the arm and relay the signal to the nerves.