More Skin, More Sun, More Tan, More Melanoma

摘要

Although personal melanoma risk factors are well established, the contribution of socioeconomic factors, including clothing styles, social norms, medical paradigms, perceptions of tanned skin, economic trends, and travel patterns, to melanoma incidence has not been fully explored. We analyzed artwork, advertisements, fashion trends, and data regarding leisure-time activities to estimate historical changes in UV skin exposure. We used data from national cancer registries to compare melanoma incidence rates with estimated skin exposure and found that they rose in parallel. Although firm conclusions about melanoma causation cannot be made in an analysis such as this, we provide a cross-disciplinary, historical framework in which to consider public health and educational measures that may ultimately help reverse melanoma incidence trends. Despite advances in its detection and treatment, melanoma remains the primary cause of mortality from skin disease in the Western world. 1,2 Improvements in the early detection of melanoma and changes in reporting practices contributed, in part, to the increase in melanoma incidence in recent decades; however, these factors alone cannot entirely account for the steady rise in tumor incidence and mortality observed during the 20th century. Several personal risk factors for developing melanoma are well established, including family history, multiple moles, fair skin, blue eyes, red hair, and freckles. 3 Environmental exposures, chiefly from UV radiation, including outdoor sunburns and indoor tanning exposure, also have been associated with increased melanoma risk. 4,5 On a population level, the contribution of changing socioeconomic factors is an intriguing variable that has not yet been fully explored, particularly the evolution of clothing styles, social norms, economic trends, available leisure time, and medical paradigms regarding UV radiation. We explore the historical relation between these factors and US melanoma incidence in the 20th century. Our goal is to illustrate how changes in fashion, perceptions of tanned skin, and socioeconomic factors have led to increased UV exposure and likely contributed to the escalation of melanoma in 20th-century America. We have divided the 20th century into 4 periods, each illustrating historical forces contributing to increases in societal exposure to UV radiation. To assess fashion and clothing trends, we reviewed artwork, consumer advertisements, and sources describing Sears department store clothing catalogs. 6–9 We also studied historical events and publicly available data regarding Americans’ leisure time and participation in outdoor activities. In an effort to illustrate the association between changing clothing styles, skin exposure to UV radiation, and the increasing melanoma incidence, we estimated skin exposure with the “rule of nines,” a standardized system traditionally used to assess percentage of body surface affected by burns. 10 We then examined the relation between skin exposure and melanoma incidence. Although they may not capture all regional, geographic, and individual subpopulation variations in UV exposure and cancer incidence rates, we used data from the Connecticut Tumor Registry, 11,12 the oldest available US cancer registry, from its inception in 1935 to the present and the Surveillance Epidemiology and End Results (SEER) national cancer database, which incorporates population-level data from 9 to 17 different regions in the United States, depending on the time period analyzed. 11,13,14 Because the average age at diagnosis of melanoma during these decades is 50 to 60 years and early-life UV exposure is known to contribute to subsequent melanoma development, we used a postexposure lag time of 50 to 60 years in our analysis. We also explored additional societal factors that (1) led to the dramatic shift in perception of tanned skin from unattractive to desirable, (2) compelled the public to continue tanning despite evidence of the carcinogenic effects of UV exposure, and (3) sustained the indoor tanning fad of the late 20th century.