Of the 3,289 participants with incident primary melanomas in the GEM study, 2,746 (83.5%) had slides available for review. After pathology slide review, participants were excluded if solar elastosis was not scored due to insufficient adjacent tissue (N = 95) or if the lesion was judged not to be melanoma by the reviewing pathologist (N = 62). The 2,589 (94.3% of 2,746) melanomas included had histologic solar elastosis adjacent to their melanoma scored as absent, mild-moderate or severe; 1,805 (69.7%) had solar elastosis present. The mean age of these 2,589 participants was 58.9 years and 56.4% were male. Most sites of melanoma were on the trunk (43.0%), while the lower extremities (19.8%), upper extremities (18.5%) and head and neck (18.1%) had approximately equal proportions; site was unknown for 0.6%.
Risk of solar elastosis increased substantially with age to OR, 11.91 at 70+ years, with reference to 11-40 years () and the OR for each year of age was 1.05 (95% CI, 1.04-1.06). More men than women had solar elastosis (59.6% vs. 49.0%) although the OR for solar elastosis in men, relative to women, was close to 1.0 when adjusted for age and study center. The odds for solar elastosis by tertile of age were reasonably similar for men and women together and separately although the increase with age was steeper in women than men (; P for interaction 0.05). Solar elastosis was more common on the head and neck and arms than the trunk or legs (P < 0.001) ().
Age, sex and bodysite in relationship to histologic solar elastosis in participants in the GEM study (N = 2,589)
Dark hair (OR, 1.38; 95% CI, 1.08-1.77) and light eye color (OR, 1.37; 95% CI, 1.04-1.80) showed the strongest evidence of a positive association with solar elastosis when all phenotypic variables were fitted together in one model adjusted for age, sex and center. There was weaker evidence that odds of solar elastosis increased with red hair (OR=1.21) and skin that sunburned with blistering (OR=1.47) (). When site-specific UVE dose was also included in the multivariable model, the effects of hair and eye color weakened and there was evidence of a stronger trend in the odds for solar elastosis as tanning ability decreased or sunburning increased (). The effects of the pigmentary variables were substantially similar when examined in a multivariable model of all pigmentary variables (as in ) and when each variable was examined separately adjusted only for age, sex and center (results not shown).
Pigmentary characteristics as correlates of histologic solar elastosis in participants in the GEM study (N = 2,434).
Having >10 nevi on the back, relative to <10, reduced the odds of solar elastosis (OR, 0.80; 95% CI 0.65-0.98; P value = 0.03) and was little changed when adjusted for pigmentary variables except the P value was 0.07 (data not shown). The addition of site-specific UVE dose caused the effect of back nevi to strengthen a little to OR, 0.77 (95% CI, 0.61-0.97) for >10 nevi (P = 0.03). In additional analyses, we found that the reduced odds for solar elastosis associated with the nevus propensity was mainly present for the trunk, arms and legs (OR, 0.75; 95% CI 0.59-0.96; P = 0.02) and was not at all evident for the head and neck (OR, 1.12; 95% CI 0.36-3.49; P = 0.84), but the P value for interaction was 0.61.
Age was strongly and independently associated with elastosis in a model including site-specific UVE, phenotypic variables and back nevi. The addition of these variables, however, reduced the odds for age by 1% for each year of age from OR, 1.06 to OR, 1.05 (95% CI 1.04-1.06) and by 35% at 70 years and older from OR, 11.91 to OR, 7.69 (95% CI 5.14-11.52), relative to 11-40 years, for men and women together and somewhat more in women (−40%) than men (−25%) of this age.
Solar elastosis was associated most strongly with estimates of cumulative sun exposure to the body site. Site-specific sun exposure hours increased the odds for solar elastosis to an OR of 5.12 for the top exposure quartile (Q4; P value for trend < 0.001; ) and the OR for the continuous measure was 1.05 (95% CI, 1.03-1.06; P < 0.001) for each 1000 site-specific hours. Inclusion of ambient UVE in this measure to give site-specific UVE dose increased the OR to 5.20 for Q4 () and the OR for the continuous measure was 1.11 (95% CI, 1.08-1.14; P < 0.001) per MJ/m2. Total outdoor hours without consideration of exposure of the body site or UVE increased the odds for solar elastosis to an OR of 2.13 for Q4 (P value for trend < 0.001) while cumulative ambient UVE, as a non-specific measure based only on places of residence, had no evident association with solar elastosis (OR, 1.29 for Q4; P for trend = 0.49) although the inclusion of center as a covariate to account for different pathology reviewers in different centers would have substantially limited between subject variation in UVE in this analysis. We also examined site-specific UV dose for hours spent in beach and water activities as a measure of recreational sun exposure. The odds for the highest exposure tertile, with reference to no beach and water activities, was OR, 2.37; 95% CI 1.70-3.30; P for trend <0.001. All sun exposure models were adjusted for age, sex, center and all phenotypic variables; site-specific measures were also adjusted for body site.
The relationships between solar elastosis and lifetime cumulative sun exposure measures in participants in the GEM study (N = 2,304).
Site-specific UVE appears to be the best predictor of solar elastosis in these data. For exposure in quartiles (), the AICc was lowest for site-specific UVE (AICc = 2006), although little different to the value for site-specific sun exposure hours (AICc = 2007). Total sun exposure hours without site specificity did not fit the data well (AICc = 2279). The evidence that site-specific UVE was the best measure of UV exposure was stronger when exposure measures were modeled as continuous variables (AICc = 1994 for site-specific UVE, 1999 for site-specific exposure hours and 2278 for total exposure hours only). This hierarchy of cumulative sun exposure measures is clearly evident when ORs for exposure in 8 categories are plotted graphically for all body sites together ().
In separate analyses by body site, the odds for solar elastosis were high for site-specific UVE to the head and neck (OR, 1.70; 95% CI, 0.26-11.13 for Q2; OR, 4.13; 95% CI, 0.71-24.14 for Q3; OR, 17.95; 95% CI, 2.52-128.15 for Q4; P = 0.002) while the odds for the trunk, arms and legs were overall similar to the estimates in all participants (OR, 1.70; 95% CI, 1.26-2.30 for Q2; OR, 2.24; 95% CI, 1.60-3.12 for Q3; OR, 4.88; 95% CI, 3.13-7.62 for Q4; P < 0.001). The P for interaction by body site was 0.23. Almost all lesions on the head and neck (94%) were positive for solar elastosis and most (59%) were rated as severe. After excluding head and neck lesions, the estimates for exposure categorized in eighths were very similar to those presented for all lesions in . All models were adjusted for age, sex, center and phenotypic characteristics.
Sunburn history showed no evidence of an association with solar elastosis in separate analyses of any site-specific painful sunburn (OR, 1.02; 95% CI, 0.79-1.32; P = 0.88) or blistering sunburn (OR, 0.95; 95% CI, 0.70-1.31; P = 0.77) relative to none in each case. Site-specific sunscreen use similarly had no apparent association with solar elastosis (OR for ever use, 1.18; 95% CI, 0.94-1.48; P = 0.15). In separate analyses of site-specific UVE in users and non-users of sunscreen on the site, ORs in users were lower (OR, 1.32; 95% CI, 0.89-1.98 for Q2; 2.22; 95% CI, 1.40-3.53 for Q3; 4.53; 95% CI, 2.40-8.53 for Q4; P for trend <0.001) than in non-users for each exposure category, especially Q4 (OR, 2.06; 95% CI, 1.21-3.50 for Q2; 2.81; 95% CI, 1.64-4.83 for Q3; 8.47; 95% CI, 4.16-17.23 for Q4; P for trend <0.001) (P for interaction = 0.09). All analyses were adjusted for age, sex, center and phenotypic variables; the model for sunburn also included site-specific UVE and body site, and the model examining site-specific UVE by sunscreen use also included body site.