I started this blog(site) because I like to go beyond headlines and explain things to people from a health educator stand point. That passion is one of the reasons I went back to school. I want to improve my skills in reading, evaluating, and reporting research. In time, I could be making my own headlines.
Well, it seems that my critical thinking has improved, though it doesn't necessarily lead to better explanations of research articles. In fact, tonight I found myself going back and forth chasing down all sorts of validity issues with the survey results presented in this article.
I have spoken out about the dangers of tanning and tanning beds in the past. I do not question the results of this study that young white women tan too much and that the risk for melanoma is increased by this use.
My first questions were about the survey itself. (I just completed a course about survey design research).
We can see that 3800 women ages 14 thru 22 responded to the survey. It was an online survey and it was meant for white women. The survey results summarized in the link above are as follows: of those women who responded, 32% have visited a tanning salon and 25% of that number do so once a week. The article also states that 81% of the women tan both indoors and outdoors - this is unclear, but I think that it is 81% of the 32%. You can do all that math.
So how were the surveys disseminated? How did the research agency target them? Who didn't respond? In survey research, we always want to know if there is something different about those who did not respond. Also the results noted much higher use in the older girls, older being 18-22. Some places have limits on the use of the beds by age - so that is important to note when giving results. Anyways - I could not find those answers - no sample characteristics or research design is provided - the study is not published in a journal which leads me to believe it was more like a little poll.
Then I looked at this 75% increase from the use of the beds. The American Cancer Society provides the rate of risk by various age groups for the ten most common cancers - you can see it here. If we look at life time risk of melanoma for women, it is 1.79. Thus the 75% increase, would be 1.79 + (1.79 * .75) = 3.13. That is a 3 % lifetime risk of this type of skin cancer, if you use tanning beds. I got a little shock when I looked at the top of the cancer chart - our lifetime risk for getting cancer of ANY type is 50% for males and 33% for females.
But again, if you go down the column on the right - 1 in 56 (the average melanoma risk) is about the fifth highest cancer incidence for women - the top is breast cancer at a 1 in 8 chance (1.2%).
As I was searching for information, I saw where the state or city of NY is attempting to ban the beds or ban them for girls under the age of 18. The legislator behind the bill has been a lifeguard and has had melanoma. He was quoted as saying that melanoma was the most common cancer. That is not true and I cannot figure out where it is coming from, because the CDC had the same statement, but the same real cancer numbers as the ACS.
By number of new cases per year and cases of death per year, melanoma falls quite short of being the most common. It comes after lung, colon, breast and prostate. I have shared this cancer chart with you in the past, but take another look. The only thing I can think of is that melanoma is the most prevalent. Meaning people keep being diagnosed with it and not dying from it so that at any given time it is the cancer that most Americans have. Make sense?
And to my dear math friend who reads my blog - if I did that 75% thing wrong PLEASE correct me :)
I have a very early flight tomorrow and have no idea why I am still sitting at my desk - but I will log off now and dream of my day at the beach tomorrow ...
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