Elsevier

Annals of Epidemiology

Volume 18, Issue 8, August 2008, Pages 614-627
Annals of Epidemiology

Sunburns and Risk of Cutaneous Melanoma: Does Age Matter? A Comprehensive Meta-Analysis

https://doi.org/10.1016/j.annepidem.2008.04.006Get rights and content

Purpose

Sunburns are an important risk factor for melanoma and those occurring in childhood are often cited as posing the greatest risk. We conducted a meta-analysis to quantify the magnitude of association for melanoma and sunburns during childhood, adolescence, adulthood and over a lifetime.

Methods

After reviewing over 1300 article titles and evaluating 270 articles in detail, we pooled odds ratios from 51 independent study populations for “ever” sunburned and risk of cutaneous melanoma. Among these, 26 studies reported results from dose-response analyses. Dose-response analyses were examined using both fixed-effects models and Bayesian random-effects models.

Results

An increased risk of melanoma was seen with increasing number of sunburns for all time-periods (childhood, adolescence, adulthood, and lifetime). In an attempt to understand how risk between life-periods compares, we also report these same linear models on a scale of five sunburns per decade for each life-period. The magnitude of risk for five sunburns per decade is highest for adult and lifetime sunburns.

Conclusions

Overall, these results show an increased risk of melanoma with increasing number of sunburns during all life-periods, not just childhood. Prevention efforts should focus on reducing sunburns during all life-periods.

Introduction

Ultraviolet radiation (UVR) is considered the foremost environmental cause of cutaneous melanoma (CM). Most dermatologists and melanoma researchers agree that sunburns are an important risk factor for CM. In particular, sunburns occurring during childhood are often cited as posing the greatest risk for CM. Armstrong (1) in a 1988 review outlined strong evidence for a hypothesis put forward by Elwood and Hislop (2) that CM risk was associated with intermittent sun exposure. These early reviews found less clear evidence for cumulative sun exposure. Armstrong theorized that at low frequencies of sun exposure, a tan is not maintained (1). Tanned skin may be a mechanism to shield melanocytes from UVR, similar to the protection seen in naturally darker skin. With intermittent exposure to the sun, the skin is more vulnerable to the effects of UVR and exposure may result in sunburn. Thus, we are examining sunburns as a marker for intermittent sun exposure.

Quantification of the magnitude of risk by life-period may help dispute that only childhood sunburns matter. Although there have been previous meta-analyses of sunburns and CM risk, none have examined the dose-response effects. We believe that pooling “ever” sunburned separately from dose-response analyses and using all categories from original studies in the dose-response analyses is more appropriate and offers more information about the association between sunburns and CM. The purpose of this meta-analytic review was to quantify the overall magnitude of association between CM and increasing number of sunburns for different life-periods of exposure.

Section snippets

Literature Search

Analytic studies that measured sunburns in relation to CM were eligible for this meta-analysis. We repeatedly searched the PubMed database through December 2007 for articles with key words related to melanoma and sun exposure including sun, sunlight, tanbed, sunbed, artificial UV, and sunburn, along with references in relevant articles. Titles and abstracts from over 1,300 articles were screened to exclude case reports, commentaries or editorials, animal studies, therapies, biological aspects

Results

We pooled 51 studies in one or more analyses 3, 4, 17, 18, 19, 20, 21, 22, 23, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79. Among these, 16 were population-based studies. Often, recruitment included all cases (41% of studies) and randomly selected controls (53% of studies). Exclusion or inclusion of in-situ cases was often unreported

Discussion

This review and meta-analysis is the first to pool data on the number of sunburns in relation to CM. Other analyses have considered sunburn to be a dichotomous exposure of either ever/never or lowest versus highest category of sunburns. Our pooled analyses of dose-response data on number of sunburns provide evidence for causality (81). Even with misclassification known to exist in ordered categories, an estimation of numbers of sunburns will give a better characterization of the true

Conclusions

This meta-analysis pooled ORs from 51 studies on CM and “ever” experiencing a sunburn. Our analyses further examined linear dose-response data among 26 studies, which had not previously been reported. These results suggest increasing number of sunburns increase the risk of CM regardless of when they are received. The large ORs seen per decade for adult and lifetime exposure suggest that it is the number of sunburns that increases melanoma risk not when they are received. More consistency may be

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    This research was supported in part by the National Cancer Institute (grant number: CA88834-01) and by the American Cancer Society (grant number: RSGPB CPPB-0400801).

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