Individuals’ Risk of Melanoma Increases with Time Outdoors, Especially in High-Sunlight Areas

    (BlackDoctor.org) — Researchers have shown for the first time that
    individual risk of melanoma, the most serious form of skin cancer, is associated
    with the intensity of sunlight that a person receives over a lifetime. Published
    in the journal Cancer Research*, the study also indicates that the risk of
    melanoma for non-Hispanic whites increases with increased time outdoors – even
    for men and women who can develop a deep tan.

    Scientists have long recognized that rates of melanoma are higher in areas
    that are closer to the equator or receive more sunlight, and that ultraviolet-B
    rays are the primary cause of sunburn and skin cancer. In this study, the
    authors developed a novel approach to measure an individual’s sun exposure over
    a lifetime, taking into account where an individual has lived throughout his or
    her life. This information determines average annual UVB intensity – the average
    amount of ultraviolet-B rays that a person could be exposed to per year over his
    or her lifetime. The data led the researchers to conclude that a 10 percent
    increase in the average annual intensity was associated with a 19 percent
    increase in the individual’s risk for melanoma in men and a 16 percent increase
    in women, at any age.

    “We’re learning more about the kinds of exposures that cause melanoma,” said
    Thomas Fears, Ph.D., the first author of the paper and a scientist at the
    National Cancer Institute in Bethesda, Md. “The risk of melanoma is greatest for
    people who develop little or no tan. However, we’ve learned that where people
    live as both kids and adults and how much UVB shines in those places are
    important factors – regardless of tanning ability.”

    According to Fears, it is not unusual to see at least a 10 percent difference
    in intensity between two locations. New Orleans, for example, receives 20
    percent more UVB each year than Atlanta.

    In addition to estimating individual risk, the authors analyzed the number of
    hours that study participants spent outdoors. They found that the number of
    summer hours spent outside prior to age 20 was much larger than after age 20. In
    light of this distinction, the researchers hypothesized that differences in
    melanoma risk previously attributed to the “critical period” of childhood may,
    in fact, be due to the larger number of hours that children typically spend
    outdoors compared to adults.

    “Studies such as this one serve as a reminder of the importance for adults
    and children alike to develop good, lifelong habits for protecting themselves
    from skin-damaging sun exposure,” said Health and Human Services Secretary Tommy
    G. Thompson. “We are now seeing that not only length of sun exposure, but also
    the intensity of the sun’s rays can affect one’s risk of melanoma.”

    This study included 718 melanoma patients recruited from the Hospital of the
    University of Pennsylvania, in Philadelphia, and from the University of
    California in San Francisco. The comparison group included 945 non-melanoma
    patients from those areas. The researchers limited the analysis to non-Hispanic
    whites because the numbers of cases in other racial/ethnic groups were too few
    for analysis.

    Each participant was interviewed in person to gather data including tendency
    to sunburn and ability to tan, along with medical, occupational, residential and
    outdoor exposure histories. Residential histories were constructed in six-month
    intervals, from date of birth to date of interview. Robertson-Berger (RB)
    meters, which measure the amount of solar radiation received in a particular
    location, were used to estimate the UVB intensity. A person’s cumulative
    intensity was estimated by adding up the RB counts for each residence location
    in six-month increments. Average annual intensity was determined by dividing the
    cumulative intensity by the person’s age in years.

    Future analyses will examine the effects of intermittent exposures on
    individual melanoma risk. For example, researchers will consider whether people
    who remain indoors for much of the week and then spend large amounts of time
    outdoors over the weekend or during a vacation are at higher risk of
    melanoma.

    An estimated 53,600 people will be diagnosed with melanoma in the United
    States in 2002, and an estimated 7,400 people will die of the disease. Melanoma
    can be cured if detected and treated early.

     

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