From Medscape Dermatology > Viewpoints
Graeme M. Lipper, MD
Arch Dermatol. 2009;145:989-996
The association among light-skin phototypes, heavy sun exposure, and cutaneous malignant melanoma (MM) is well established.
Excessive childhood ultraviolet B exposure leads to increased MM incidence later in life.[1-3]
Known risk factors for the development of MM include: a family history of MM, the presence of dysplastic nevi (or family history of dysplastic nevus syndrome), presence of numerous melanocytic nevi, and a history of heavy sun exposure.[2-4] Because individuals with numerous melanocytic nevi are at increased risk of developing MM, Aalborg and colleagues sought to determine if children with light-skin phototypes who tan are at greater risk than their nontanning peers of developing multiple nevi, and by proxy, MM later in life.
This prospective study began with a cohort of 1145 children (ages 5-6 years) recruited from the Denver metropolitan area during 2003 and 2004. Of this initial group, 696 children completed 3 consecutive annual skin examinations. Investigators further reduced this cohort by excluding patients with red hair (considered to be a genetically distinctive group with a low baseline incidence of nevi), incomplete data, or darker skin phototypes. The remaining study population was composed of 131 very light-skinned white children without red hair and 444 darker-skinned white children without red hair. Investigators followed this cohort for the development of melanocytic nevi for 3 years. Of note, skin pigmentation was objectively determined with colorimetry analysis (Chroma Meter CR-400, Konica Minolta Sensing Americas, Inc, Ramsey, New Jersey). By comparing the skin pigmentation in photoprotected (axillary) vs photoexposed (forearm) areas of skin, investigators further stratified very light-skinned children into 2 subgroups: low tanners (n = 20) and high tanners (n = 111).
During the 3-year follow-up period, Aalborg and colleagues noted the following:
Very light-skinned children who tanned had significantly more nevi develop compared with their nontanned peers.
Minimally tanned light-skinned children had mean nevus counts of 14.8 at 6 years, 18.8 at 7 years, and 22.3 at 8 years. In contrast, light-skinned children who tanned had mean nevus counts of 21.2 at 6 years, 27.9 at 7 years, and 31.9 at 8 years.
The aforementioned association was independent of variables such as the child's base skin color, hair color, eye color, parent-reported sun exposure, hours per week in the sun, sun protection behavior, past sunburns, and vacation sun exposure.
Darker-skinned white children showed no relationship between tanning and number of nevi.
Are children with light-skin phototypes who tan at greater risk of developing melanoma later in life than their nontanned peers?
Previous studies have already shown that among white children, those with lighter-skin phototypes are 2-3 times more likely to have MM develop than those with darker-skin types.
In addition, studies of light-skinned white children in Europe and Canada have demonstrated a clear association between a history of multiple or severe (blistering) sunburns and high nevi counts.[5,6]
Aalborg and colleagues now add to this important body of knowledge by showing that light-skinned white children who tan clearly develop a greater number of melanocytic nevi than their nontanned peers, even at an early age.
Because many MMs do not occur within existing nevi, the presence of multiple nevi in these young children likely serves as a marker for ultraviolet-induced skin damage and/or a genetic susceptibility to MM.
In this context, it seems clear that parents of light-skinned children should be educated about the benefits of photoprotecting their children to avoid tanning, starting at an early age.