Positive interaction between light iris color and ultraviolet radiation in relation to the risk of uveal melanoma: a case-control study.
OBJECTIVE
To examine the association among phenotypic characteristics, chronic and intermittent ultraviolet (UV) radiation, and the risk of uveal melanoma.


METHODS
Case-control study.


METHODS
Overall, between September of 2002 and March of 2005, 1677 eligible subjects (age range: 20-74 years, living in Germany) participated. Interviews were conducted with 459 incident uveal melanoma cases (response proportion 94%), 827 population controls (55%), 180 ophthalmologist controls (52%), and 187 sibling controls (57%).


METHODS
Data on phenotypic characteristics and chronic and intermittent UV radiation exposure were obtained from a self-administered postal questionnaire and computer-assisted telephone interview. We used conditional logistic regression to estimate odds ratios adjusting for the matching factors. Furthermore, we studied the presence of synergy (super additive of risk or relative excess risk due to interaction) between light iris color and several UV radiation exposures.


METHODS
Hair color at age 20 years, eye color, untanned skin color, ability to tan, propensity to burn on exposure, freckling, occupational sun exposure, artificial UV radiation, burns to the eyes.


RESULTS
In all 3 control groups, fair skin color, freckling as a child, nevi on the upper arms, burns to the eyes, use of sunlamps, and ever worked outside for 4 or more hours per day were positively associated with uveal melanoma. The association with eye color was apparent only in population controls (odds ratio = 1.9; 95% confidence interval [CI], 1.4-5.2), resulting in a relative excess risk due to interaction of 0.9 (95% CI, -0.6-2.3) for light iris color and more than 5 eye burns (UV-related keratitis) and 0.6 (95% CI, -0.3 to 1.5) for light iris color and eye protection.


CONCLUSIONS
Our interaction analyses suggest that there is an etiologic synergism between light iris color and the exposure of UV radiation. People with light iris color may have an especially increased risk for uveal melanoma if they are exposed to UV radiation.


BACKGROUND
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Schmidt-Pokrzywniak
Andrea
A
Clinical Epidemiology Unit, Institute of Medical Epidemiology, Biometry and Informatics, Medical Faculty, University of Halle-Wittenberg, Halle, Germany. andrea.schmidt-pokrzywniak@medizin.uni-halle.de
Jöckel
Karl-Heinz
KH
Bornfeld
Norbert
N
Sauerwein
Wolfgang
W
Stang
Andreas
A
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005127:Eye Color; D005260:Female; D005858:Germany / Q000453:epidemiology; D006200:Hair Color; D006801:Humans; D007498:Iris / Q000528:radiation effects; D008297:Male; D008545:Melanoma / Q000453:epidemiology / Q000209:etiology*; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology*; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology; D010641:Phenotype; D012307:Risk Factors; D012880:Skin Pigmentation; D011795:Surveys and Questionnaires; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014604:Uveal Neoplasms / Q000453:epidemiology / Q000209:etiology*