Cardiovascular and cancer mortality inversely associated with long-term ambient ultraviolet exposure across US Health Service Areas with UK Biobank corroboration

OBJECTIVE To assess associations of ambient UV with cardiovascular and cancer mortality across US Health Service Areas (HSAs), prioritise outcomes by signal and attributable burden, assess racial and ethnic variation, with UK Biobank corroboration. DESIGN Ecological analysis of HSAs using linear regression of crude mortality on ambient UV and social vulnerability, with correction for multiple comparisons. SETTING US HSAs and UK Biobank. DATA SOURCES Publicly available US data and UK Biobank data accessed under Application 82526. PARTICIPANTS 704 808 annual cardiovascular deaths (aged [&ge;]65) and 565 287 annual cancer deaths (aged [&ge;]50) from populations of 52.8 and 115.2 million; UK Biobank analyses included 412 665 individuals. MAIN OUTCOME MEASURES Cardiovascular, all-cancer, and body-site-specific cancer mortality; regression slope per interquartile-range increase in UV ({beta} UV/IQR), modelled attributable burden for US data, and hazard ratios for the UK Biobank data. RESULTS Higher UV was associated with lower cardiovascular ({beta}UV/IQR -68.3 deaths/100 000; P<0.001) and all-cancer mortality (-43.2; P<0.001), corresponding to 36 043 (5.1%) and 49 789 (8.8%) fewer US deaths annually, respectively. Associations varied by race and ethnicity. Cardiovascular findings were directionally consistent between US and UK datasets. All-cancer mortality and 10 of 18 cancers were inversely associated with UV in the US; UK analyses found inverse associations for all-cancer and two individual body-site-specific cancers. Twelve cancers showed directionally concordant associations across the datasets, of which ten were inverse. Lung cancer showed the strongest inverse association in each dataset. CONCLUSIONS Higher UV was associated with lower cardiovascular and cancer mortality across US HSAs, with modelled attributable burdens exceeding 5%; UK Biobank findings provided partial corroboration. Twelve of 18 site-specific cancers were directionally concordant between datasets. US race-stratified heterogeneity did not follow a skin-colour gradient, suggesting residual confounding.