Tuesday, March 29, 2011

Indoor Tanning, Outdoor Tanning and Risk of Melanoma

The following study on the risk of melanoma from tanning was recently published in the journal of Cancer, Epidemiology, Biomarkers & Prevention. The findings are worth a discussion and I have provided both some quotes from the study and some commentary.
Lazovich et al. Indoor Tanning and Risk of Melanoma: A Case-Control Study in a Highly Exposed Population. Cancer, Epidemiology, Biomarkers & Prevention 2010 19 (6); 1557-68
"Our study has several important findings. First, we found that melanoma occurred more frequently among indoor tanners compared with persons that never engaged in this activity."
"Second, we found a strong dose-response relationship between melanoma risk measured by total hours, sessions, or years."
"Third, we found an increased risk of melanoma with use of each type of tanning device as well as with each period of tanning use, suggesting that no device could be considered "safe".
"With our carefully designed questionnaire eliciting the use of specific devices that emit differing amounts of UVB and UVA, we observed considerably stronger Ors (odds ratios) for melanoma among users of high-speed or high-pressure devices than among users of conventional devices."
"Second, studies have shown that the percentage of UVB and UVA emitted depends on the type of lamp, the quality of maintenance, and the level of degradation - information that cannot be collected through retrospective recall."
"Similar to our experience, other studies that collected information about device types have not been able to single out any one type (UVA or UVB) as being higher risk than the other."
"Although disentangling which wavelength is responsible for melanoma development might not be possible in epidemiological studies, the evidence also indicates that all indoor tanning devices are harmful."
"We did not find lifetime routine sun exposure or sun exposure via recreational outdoor activities or occupations to be associated with melanoma risk, nor were these results changed by detailed examination of sun exposure according to season, decade age, type of outdoor activity, indoor tanning status, or tumor site."
"Indeed, published studies reveal that the relationship between sun exposure and melanoma is complex, and depends on whether the exposure is intermittent or chronic; inconsistencies in its measurement further complicates an understanding of these relationships."
"A meta-analysis of 57 studies and a pooled analysis of 15 studies each reported fairly weak associations between total sun exposure and melanoma, no relationship to chronic exposure (based on outdoor occupations), moderately strong associations with intermittent exposure (usually defined as sunbathing, time spent during sunny vacations, or outdoor recreational activities), and strong associations with sunburn."
"The likelihood of melanoma was significantly increased 2.86 and 4.44 times for users of high-speed/high-intensity devices and high-pressure devices respectively; and 1.76 and 1.85 times for users of conventional devices and sunlamps respectively, relative to never users."
Dr. Chestnut's Interpretation and Comments:
First of all they are very biased in the way they report their results. They SHOULD state that their study suggested an ASSOCIATED increased risk of melanoma with use of indoor tanning devices. It is very misleading to state that there is an ACTUAL increased risk. This type of study can only provide suggestive correlational data NOT definitive cause and effect data.
Second they report their figures as relative risk figures but do not provide any data on the absolute risks. What do I mean? I mean that although this study reports a correlation between indoor tanning devices and increased RELATIVE risk of melanoma these figures are not meaningful without knowledge of the absolute risk of developing melanoma. In other words if your chances of developing melanoma are 1 in a million DOUBLING your relative risk really means that you changed your absolute risk to 2 chances in a million. Not something one would really be concerned about as the increased absolute risk is so small that it could never be determined if it represented any increased real life risk at all.
So what is the absolute risk of developing melanoma? The literature reports that there is a one in 64 chance over a lifetime that a person living in America will develop melanoma. If this risk was doubled from indoor tanning that would mean that people who use indoor tanning beds would have a one in 32 chance of developing melanoma. This is worth considering. Next we need to consider how serious this is, what is the mortality rate? Well it appears that about 8% of cases are fatal. There are approximately 100,000 new cases per year and about 8,000 deaths per year associated with melanoma. What does this mean in terms of your risk? It means that in the U.S. there are about 300 million people and 8,000 of these die from melanoma in any given year. This means that in any given year your chance of dying from melanoma is one in 37,500. So if you double this relative risk from indoor tanning your absolute risk of dying from melanoma in any given year would increase from one in 37,500 to two in 37,500. Not a perfect statistical analysis as things change with age etc but you get the idea.
HOWEVER, the vast, vast, vast, vast, vast majority of melanoma cases have NOTHING to do with indoor tanning beds (most people who develop melanoma have never been in a tanning bed) SO this means that something else is causing melanoma. We also know that sun exposure is NOT the primary cause of melanoma (see bolded quotes above), even if the sun exposure is chronic. What we can say is that the chance of melanoma is strongly correlated with SUN BURNS but even sun burns only account for a small percentage of cases.
If you look closely at this study you will also see that they report a surprisingly high number of SUN BURNS caused by indoor tanning beds, especially the high-intensity devices which not coincidentally are also associated with the highest risk of melanoma.
"Cases were also more likely than controls to report having experienced painful burns from indoor tanning, a greater number of indoor tanning-related burns, or painful sunburns at a time when they thought they were protected from the sun by indoor tanning."
What does all this mean? It means that sun exposure is NOT the cause of melanoma. SUN BURN is a causal factor in the development of melanoma.It means that indoor tanning devices are likely NOT the cause of melanoma but that SUN BURN from indoor tanning devices is.
Humans genetically require sunlight; it provides vitamin D and has many other benefits. Humans are NOT supposed to get sunburned.
My advice?
Use common sense. Get sun exposure and AVOID SUN BURNS!
DON'T use toxic sunscreens, use natural oils rich in antioxidants like grapeseed oil or coconut oil or almond oil.
Don't spend money on expensive "natural" lotions or sunscreens; just buy the actual oils and some aloe vera and apply often as they come off or get absorbed.
Make sure you are sufficient in Omega 3 fats!! Omega 3 fatty acids protect your skin and of course do a million other essential things for your cells.

Exercise regularly! Research indicates that people who walk 30 minutes per day reduce their chance of melanoma by up to 70%! Walking is FREE!
Once again it all comes down to living the Innate Lifestyle - living a lifestyle that is congruent with your genetic requirements for the expression of health and the prevention of illness 

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