Jumat, 27 Juni 2008

Cell Phones and Brain Cancer

First, someone says (again) that cell phones may cause brain cancer. Then the FDA reports that there is no convincing evidence that cell phones are a health risk. (See “Experts Revive Debate Over Cellphones and Cancer”, The New York Times online, June 3, 2008.) What’s a consumer to believe?

This is a good example of the limitations of the scientific method, and why it is sometimes hard to know the truth. Regarding the first statement, yes, cell phones may cause brain cancer (and then again, they may not.) As for the second statement, it is true that there is still no scientifically convincing evidence that cell phones are a health risk. (but again, that doesn’t mean they aren’t!)

Why is it so hard to find the truth? First, brain cancers are so rare that one would have to study literally hundreds of thousands of people. Second, to do the scientific study properly, a controlled study would need to be done in which the lives of hundreds of thousands of people would have to be strictly controlled. It can’t be done. Third, no one has used cell phones for 50 years, so potential long-term effects won’t show up for awhile. And fourth, modern phones emit much less energy than the older models did.

What can we do? We can study those few patients with brain cancer and ask questions – questions about health habits, including past cell phone use. Self-reports by patients are notoriously unreliable, of course, so it may take hundreds of such studies before we consider the evidence “convincing”. We don’t need to panic, but we need to be watchful of the changing state of knowledge regarding cell phones and cancer.

You might remind your students that a similar question came up in the 1950s when smoking was actively encouraged – does smoking cause lung cancer? Who could have known that nearly sixty years later the rates of lung cancer in persons over 65 would be more than five times the rates of that same age group in 1950?!

Minggu, 08 Juni 2008

Your Bacterial Friends

How many bacteria normally live on or in your body, and what are they doing there? The government wants to know, with the goal of better understanding their roles in health and disease. So last year NIH launched the Human Microbiome Project. The early results show that bacteria and other microbes colonizing human tissues outnumber the body’s cells by ten to one! Over 600 different bacteria have been identified in such places as the vagina, belly button, nose, mouth, and digestive tract, not to mention all over the skin. And would it surprise you to know that there are more bacteria in your belly button than between your toes? Different bacteria influence our ability to fight infections, digest nutrients, and produce vitamins, plus there may be many other functions that we don’t even know about yet.

See the brief news article on this subject in Science magazine (“Bacteria are Picky About Their Homes on Human Skin”, Science May 23, 2008, p. 1001.)

Jumat, 06 Juni 2008

What Defines a Species?

That question confuses even the experts. Even Darwin couldn’t do it. In 1856 he wrote, concerning the definition of species, “It all comes, I believe, from trying to define the indefinable”.

Traditionally, biologists loosely define a species as a population whose members breed mostly among themselves under natural conditions. Generally this means that they are genetically distinct. But now that we can sequence DNA, the concept of “genetically distinct” itself is problematic - exactly how many genes or base pairs have to be different? As one species evolves to become two, when are they different enough? It’s not just a philosophical exercise; how a particular species (or group of individuals within a species) is defined may determine whether it is an “endangered species” or not, and thus worthy of protection under the law. It can mean its very survival.

For a good recent article on the subject, see “What is a Species?”, Scientific American, June 2008, pp. 72-79.

Minggu, 01 Juni 2008

GINA Finally Passes

After thirteen years of wrangling and a failed attempt last year (see this blog, May 8, 2007), Congress finally passed the long-awaited Genetic Information Nondiscrimination Act (GINA). President Bush signed it into law on May 21, 2008.

GINA makes it illegal for health insurers to deny coverage or raise premiums based on genetic information. It also prohibits employers from using genetic information in making decisions regarding job assignments, promotion, hiring, or firing. Patients and health care workers had been pushing for the bill for years, claiming that people were afraid to take genetic tests, such as the one for the breast cancer genes BRCA1 and BRCA2, because they were afraid of being denied insurance coverage or a job should they test positive.

Why did it take so long for the bill to pass? Some lawmakers, most notably Senator Tom Coburn of Oklahoma, were worried that the bill would create a windfall for trial lawyers as people sued insurance companies and employers over alleged discrimination in health care coverage. The final bill addresses that question to everyone’s satisfaction, apparently.

Teens and Energy Drinks

There’s growing concern among school officials and health care workers that teen use of energy drinks such as Red Bull and Spike Shooter are early warning signs of the willingness to take risks. According to researchers, high consumption of energy drinks is associated with aggressive and risky behaviors, including substance abuse, violence, and unprotected sex. No one is saying yet that these energy drinks cause such behaviors, but parents should probably be aware that teens who are willing to abuse caffeine may be more likely to engage in other risky behaviors as well. The research is published in the March issue of The Journal of American College Health and discussed in a recent news article (“Taste for Quick Boost Tied to Taste for Risk”, New York Times online May 27, 2008.)

The energy drink Spike Shooter contains 428 mg of caffeine in 12 ounces, or about 12x that of Coke or Pepsi and 2-5 times that in a cup of coffee. Teens have been sent to the emergency room with heart palpitations, jittery behavior, and sweating as a result of drinking too many energy drinks. Some teens are combining these drinks with alcohol in the mistaken belief that it makes them less drunk.

Do your students use energy drinks, and do they know what's in them?
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