Are tanning beds a cancer risk?

Being the scrawny white nerd that I am, I don’t tan… I burn. This concerned me greatly since I would soon be traveling to the Outer Banks in my Marine Biology class. I wanted to go swimming in the ocean, but that would mean my un-tanned, blinding white-ness would be on display. Not wanting to look completely ridiculous, I contemplated going tanning for the first time ever.

But I was worried. Tanning lotions were out because I don’t like the thought of smearing skin-altering chemicals on myself. And I had heard from many sources that tanning beds cause cancer. So I decided to look into the matter.

According to this study I found [1], exposure to tanning beds actually does increase the risk of developing malignant melanoma (skin cancer).

Where are they getting that from?
Ting and his crew wanted to test the hypothesis that increased exposure to tanning beds was linked to an increased risk of developing malignant melanoma.

To perform the study, surveys were completed by a random sample of 551 patients. The surveys asked questions like:

1. Extent of tanning bed exposure (how much of the body was exposed to the tanning bed),
2. use in the last 12 months (number of tanning sessions in the past year),
3. age at first exposure,
4. season of use (when in the year do they go tanning?),
5. lifetime number of tanning sessions,
6. minutes spent per session,
7. sun protection attitudes and practices (do they usually wear sunscreen?), and
8. leisure and occupational sun exposure (how often are they exposed to natural sunlight?).

The survey also looked at demographic information, such as:

• Gender,
• age,
• race,
• tendency to tan,
• level of education,
• work environment (indoor or outdoor),
• number of sunburns in the past, and
• previous history of various cancers.

Here is a look at the demographic information.

When doing a scientific study, you must always be wary of confounding variables (also known in statistics as a lurking variable). A confounding variable is any variable other than the independent variable that may bear any effect on the behavior of the subject being studied.
An example of a lurking variable would be testing infant memory with a matching game, but waiting too long between tests so that improved results on the second game may be due to the baby’s brain developing and not the baby’s memory. (Wikipedia)

The study took into account confounding variables such as:

• Indoor vs. outdoor occupation and leisure activities,
• Fitzpatrick skin type (numeric scale for skin color),
• history of blistering sunburn, and
• use of sunscreen and sun protective clothing.

If a patient had a family history of malignant melanoma, he was not assessed because of the potential for inaccuracy. (If their family is genetically more likely to get skin cancer without ever having used a tanning bed, than if they use tanning beds and get cancer it is impossible to determine the cause of the cancer.)

The answers to the survey were compared to those patients’ medical records. Of the 501 records available, 194 of the patients had been diagnosed with some kind of skin cancer (see Table 1).

Tables 2 and 3 below show the data that links exposure to tanning beds and risk for developing malignant melanoma.  Click on them to make them larger.

“Most modern tanning units produce mainly UV-A and less than 5% UV-B, although this amount of UV-B irradiation exceeds that in natural sunlight, and is sufficient to cause immunosuppression.” [1]
Ummm…yikes.

Interestingly, (according to Ting) this was the first study that accounted for confounding factors, and considered the frequency or duration of tanning bed exposure.
Yeah, that might help.

After they did a bunch of calculations that I won’t go into, they found that their hypothesis was correct. Increased exposure to tanning beds increased the risk of developing malignant melanoma.
Most of the patients that went tanning the most were young women under 45 years old, which meant that they were at the greatest risk of developing skin cancer.


Since exposure to tanning beds would increase my risk for developing cancer, I guess I better find a safer way to get a tan.
Of course, all of this is a moot point now that I’m already back from our OBX trip.
And yes, I did get sunburned after only an hour of kayaking.



[1]
Ting, W., Schultz, K., Cac, N. N., Peterson, M., & Walling, H. W. (2007). Tanning bed exposure increases the risk of malignant melanoma. International Journal of Dermatology, 46(12), 1253-1257.

DOI: 10.1111/j.1365-4632.2007.03408.x

Journal article LINK

The genetics of cancer

“Is cancer passed down through our genes?

If a relative has cancer, is my risk of getting cancer any higher?

If it is genetic, and I get cancer, what are the chances that I will pass it on?

Are there any tests out there for these things?”

These are all questions I found myself wondering last weekend as I worked on capsule slides in the Microbiology lab, while all the cool kids were out getting wasted.

That was when I realized I had found the topic of my second blog post for Senior Seminar.
I also realized I could really use a liquid cocaine shot.

So I started searching for answers as the snow began to pour down outside.

According to this informative website by the National Cancer Institute, “all cancer is genetic”.
What they mean by that is that all cancer arises from mutations in DNA, or altered genes. When the genes that regulate and control a cell are messed up, the cell is unable to stop replicating. It takes many steps, but if subsequent mutations occur and certain conditions are met, the cancerous cell will progress from normal, to malignant (dangerous), to metastatic (spreading).

“Cancer usually arises in a single cell. The cell's progress from normal to malignant to metastatic appears to involve a series of distinct changes in the tumor and its immediate environment, and each is influenced by different sets of genes.”[1]

But disease inheritance is very complex. Altered or damaged genes do not always get expressed in harmful ways. Different mutations, or the same mutation at different locations, will have different effects. Some will be expressed by severe symptoms, some as mild symptoms, and others will not be expressed at all.

As it turns out, cancer can be passed down if that specific damaged or mutated gene (disease-linked gene) gets passed on. If careful records are kept, a family tree mapping the expression of the disease-linked gene can be constructed. This is helpful in determining your chances of inheriting a disease-linked gene.

[http://www.cancer.gov/cancertopics/understandingcancer/genetesting/Slide24]

The good news is, most cancer is NOT inherited.
“Even though all cancer is genetic, just a small portion--perhaps 5 or 10 percent--is inherited.” [1]

This means that out of ten breast cancer patients, only one of them may have a known inherited factor. The other nine also have cancer, but due to unknown factors that are not inherited.

The Human Genome Project has successfully mapped the chemical bases of all 25,000 genes, as well as the spaces between them.
“This information can be used to determine where gene mutations occur in specific diseases.”[1]
For example, here is a chart of disease-linked genes located along the X chromosome.

With Microarray analysis, complete patterns of gene activity can be captured.
“A DNA microarray is a thin-sized chip that has been spotted at fixed locations with thousands of single-stranded DNA fragments corresponding to various genes of interest. A single microarray may contain 10,000 or more spots, each containing pieces of DNA from a different gene. Fluorescent-labeled probe DNA fragments are added to ask if there are any places on the microarray where the probe strands can match and bind.” [1]

I also found that genetic tests for a wide array of disorders, not just cancer, are already widely used. For instance, newborn babies are commonly screened for a variety of disorders with genetic tests.

There are three different genetic test methods:

1. Chromosome test – detect changes to whole chromosomes.
2. DNA test – examine short stretches of DNA within genes.
3. Protein test – look for protein products of genes.

[http://www.cancer.gov/cancertopics/understandingcancer/genetesting/Slide18]

The only downside to genetic testing is that they find mutations, not the disease itself.
For instance, having an altered gene may increase your chances of getting the disease, but that does not mean that you absolutely, positively WILL develop that disease. It is entirely possible that you will live the rest of your life without ever developing that disease, while someone with a non-altered gene does develop it.
If all I did was confuse you more, this slide may help.

All my questions had been answered.
Since alcohol is banned in the dorms, I celebrated by slamming back a glass of Ocean Spray’s Cran-Grape juice and went to bed.


{For the original slideshow by the National Cancer Institute (where I got this information), click here.}

[1] National Cancer Institute website.