Tanning beds: Shine a light on some facts.

Doesn’t the Saskatchewan NDP have bigger issues to worry about than banning teens from using tanning beds?

This is one of those issues that where everyone “knows” what they know but few bother to actually look up the facts.

In a well-designed Minnesota study published in the Cancer Epidemiology, Biomarkers, & Prevention, Lazovich et al. reported an increased odds ratio of 1.75 associated with ever use of tanning beds.  Odds ratio is an estimate of risk although it tends to be an overestimate.  This finding is similar to the 2.06 reported in a nested case-control study (an even better design*) from the Nurses’ Health Study.  Based on an odds ratio of 1.75, the risk of developing melanoma is estimated 75% higher for someone who uses a tanning bed compared to someone who doesn’t use a tanning bed.  Therefore, some of the people who use a tanning bed and are later diagnosed with melanoma would have still developed melanoma even if they had not used a tanning bed.

Some numbers:

  • Incidence of melanoma in Saskatchewan in 2003 was approximately 11 cases per 100,000 people (based on 106 cases).  Mortality was 2 deaths from malignant melanoma per 100,000 people.
  • 27% of women ages 16 – 24 in Saskatchewan use tanning beds (from SunSmart Saskatchewan).
  • In the MN study, only 18% of cases used a tanning bed before age 18 and first use before age 18 was not associated with a greater risk of melanoma. (Sorry MLA Chartier.)
  • The incidence of melanoma in the US has been increasing for almost 20 years but the mortality rate has remained relatively constant.

Therefore … banning tanning beds before age 18 would prevent almost precisely zero cases of melanoma.  Doubly true if a teen denied access to a tanning bed just decides to tan outside without sunscreen instead.  Maybe if the person denied access to tanning as a teen never uses a tanning bed after turning 18, a few cases of melanoma might be prevented.

Also, your risk of developing melanoma this year is 0.011%.  If you never use a tanning bed and assuming that the risk estimates in the studies actually reflect the true risk, your risk of developing melanoma this year is 0.008%.  That’s not a huge change in absolute risk.

* A retrospective case-control study compares the exposure rate in people with disease to that in people without disease.  Because people are asking to report exposures from sometime in the past, there is recall bias which affects the estimate of risk.  People with disease are more likely to recall negative exposures.  A nested case-control study uses prospective data on exposure which was collected before disease started which removes the potential for recall bias.

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