Genetics of Skin Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Melanoma
Table 5. Meta-Analysis Results: Intermittent and Chronic Sun Exposure and Melanoma Risk
|Study Citation||Intermittent Sun Exposure (OR, 95% CI)||Chronic Sun Exposure (OR, 95% CI)||Comments|
|CI = confidence interval; OR = odds ratio.|
|Nelemans et al.||1.6 (1.3–1.9)||0.7 (0.6–0.9)||Lack of standardized measures an issue.|
|Elwood et al.||1.7 (1.5–1.9)||0.9 (0.8–0.9)||Mechanisms for the differences in types of sun exposure not understood.|
|Gandini et al.||1.6 (1.3–1.9)||0.9 (0.7–1.0)||None.|
Although these meta-analyses have yielded very similar risk estimates, the measurement of sun exposure is complex; new studies using comparable protocols in different populations with varying levels of sun exposure are needed.
One explanation offered for the rise in melanoma incidence relates to the differential effects of chronic and intermittent sun exposure; as people have replaced outdoor occupations with indoor occupations, they have engaged in more intermittent sun exposure. Data from very different settings seem to suggest that intermittent sun exposure is critical to the risk of developing melanoma.
The evidence relating lifetime cumulative exposure to melanoma risk comes from two sources: migrant studies and studies of lifetime exposure, controlling for intermittent and occupational exposure. Data from Australia and Italy show that individuals who migrate from areas of low exposure to ultraviolet (UV) radiation, such as the United Kingdom, to areas of high exposure, such as Australia or Israel, before they reach age 10 years have a lifetime risk of developing melanoma that is similar to that of people in the new country.[8,9,10] Alternatively, adolescents or older individuals who migrate from areas of low solar exposure to areas of high solar exposure have a risk that is more similar to that of people from their area of origin than to that of people in the new area. These data have often been cited as indicating that childhood sun exposure is more important than adult sun exposure in melanoma development. However, the data could also be interpreted as suggesting that the length of high-level exposure is more critical than the age at exposure. Thus, people who migrate early in life to a high-insolation region have a longer potential period for intense exposure than do those individuals who migrate later in life.