Sun exposure and melanoma risk at different latitudes: a pooled analysis of 5700 cases and 7216 controls

Abstract

Background: Melanoma risk is related to sun exposure; we have investigated risk variation by tumour site and latitude.

Methods: We performed a pooled analysis of 15 case-control studies (5700 melanoma cases and 7216 controls), correlating patterns of sun exposure, sunburn and solar keratoses (three studies) with melanoma risk. Pooled odds ratios (pORs) and 95% Bayesian confidence intervals (CIs) were estimated using Bayesian unconditional polytomous logistic random-coefficients models.

Results: Recreational sun exposure was a risk factor for melanoma on the trunk (pOR = 1.7; 95% CI: 1.4-2.2) and limbs (pOR = 1.4; 95% CI: 1.1-1.7), but not head and neck (pOR = 1.1; 95% CI: 0.8-1.4), across latitudes. Occupational sun exposure was associated with risk of melanoma on the head and neck at low latitudes (pOR = 1.7; 95% CI: 1.0-3.0). Total sun exposure was associated with increased risk of melanoma on the limbs at low latitudes (pOR = 1.5; 95% CI: 1.0-2.2), but not at other body sites or other latitudes. The pORs for sunburn in childhood were 1.5 (95% CI: 1.3-1.7), 1.5 (95% CI: 1.3-1.7) and 1.4 (95% CI: 1.1-1.7) for melanoma on the trunk, limbs, and head and neck, respectively, showing little variation across latitudes. The presence of head and neck solar keratoses was associated with increased risk of melanoma on the head and neck (pOR = 4.0; 95% CI: 1.7-9.1) and limbs (pOR = 4.0; 95% CI: 1.9-8.4).

Conclusion: Melanoma risk at different body sites is associated with different amounts and patterns of sun exposure. Recreational sun exposure and sunburn are strong predictors of melanoma at all latitudes, whereas measures of occupational and total sun exposure appear to predict melanoma predominately at low latitudes.

Figure 1

Forest plots of the association between (A–C) the highest sun-bathing exposure and (D–F) the highest total recreational sun exposure and melanoma risk. Each line represents results from an individual study, with the length of the horizontal line indicating the 95% CIs, and the square box indicating the study-specific adjusted OR (OR2) for the ‘High vs Low’ recreational sun-exposure category. Adjusted pOR2s and 95% CIs are represented by grey diamonds

Figure 2

Forest plots of the association between the highest occupational sun exposure and melanoma risk. Each line represents results from an individual study, with the length of the horizontal line indicating the 95% CIs, and the square box indicating the study-specific adjusted OR (OR2) for the ‘High vs Low’ occupational sun-exposure category. Adjusted pOR2s and 95% CIs are represented by grey diamonds

Figure 3

Forest plots of the association between total sun exposure and melanoma risk by tumour sites. Each line represents results from an individual study, with the length of the horizontal line indicating the 95% CIs, and the square box indicating the study-specific adjusted OR (OR2). Adjusted pOR2 and 95% CIs are represented by grey diamonds

Figure 4

Forest plots of the association between (A–C) ever sunburn before age 15 and (D–F) ever sunburn after age 20 and melanoma risk by tumour sites. Each line represents results from an individual study, with the length of the horizontal line indicating the 95% CIs, and the square box indicating the study-specific OR (OR1). pOR1s and 95% CIs are represented by grey diamonds