Skin cancer as a marker of sun exposure associates with myocardial infarction, hip fracture and death from any cause

Background Sun exposure is the single most important risk factor for skin cancer, but sun exposure may also have beneficial effects on health. We tested the hypothesis that individuals with skin cancer (non-melanoma skin cancer and cutaneous malignant melanoma) have less myocardial infarction, hip fracture and death from any cause, compared with general population controls. Methods We examined the entire Danish population above age 40 years from 1980 through 2006, comprising 4.4 million individuals. Diagnoses of non-melanoma skin cancer (n = 129 206), cutaneous malignant melanoma (n = 22107), myocardial infarction (n = 327 856), hip fracture (n = 129 419), and deaths from any cause (n = 1 629 519) were drawn from national registries. Results In individuals with vs without non-melanoma skin cancer, multifactorially adjusted odds ratios were 0.96 (95% confidence interval: 0.94-0.98) for myocardial infarction and 1.15 (1.12-1.18) for hip fracture, and the multifactorially adjusted hazard ratio was 0.52 (0.52-0.53) for death from any cause. Risk of hip fracture was reduced (odds ratios were below 1.0) in individuals below age 90 years. In individuals with vs without cutaneous malignant melanoma, corresponding odds ratios were 0.79 (0.74-0.84) for myocardial infarction and 0.84 (0.76-0.93) for hip fracture, and the corresponding hazard ratio for death from any cause was 0.89 (0.87-0.91); however, cutaneous malignant melanoma was associated positively with death from any cause in some individuals. Conclusions In this nationwide study, having a diagnosis of skin cancer was associated with less myocardial infarction, less hip fracture in those below age 90 years and less death from any cause. Causal conclusions cannot be made from our data. A beneficial effect of sun exposure per se needs to be examined in other studies.