title: The relationship between ultraviolet light exposure and mortality in dialysis patients.
abstract: BACKGROUND
  Emerging data suggest that reduced exposure to ultraviolet (UV) radiation is associated with increased mortality in the general population. To date, the association between UV exposure and mortality in dialysis patients has not been examined.
  
  
  METHODS
  We examined the association between UV index, a proxy of UV exposure, and all-cause mortality among 47,286 US dialysis patients (entry period 2001-2006, with follow-up through 2009) from a large national dialysis organization using multivariable Cox regression. The UV index was ascertained by linking individual patients' residential zip codes to National Oceanic and Atmospheric Administration data, and was categorized as low (0-<3), moderate (3-<5), moderate-high (5-<6), high (6-<7), and very-high (≥7). In secondary analyses, we examined the UV index-mortality association within subgroups of age (<65 vs. ≥65 years old), sex, and race (white vs. non-white).
  
  
  RESULTS
  The study population's mean ± SD age was 60 ± 16 and included 46% women and 56% diabetics. Compared to patients residing in moderate-high UV index regions, those residing in high and very-high UV index regions had a lower mortality risk: adjusted HRs 0.84 (95% CI) 0.81-0.88 and 0.83 (95% CI) 0.75-0.91, respectively. A similar inverse association between UV index and mortality was observed across all subgroups, although there was more pronounced reduction in mortality among whites vs. non-whites.
  
  
  CONCLUSIONS
  These data suggest that dialysis patients residing in higher UV index regions have lower all-cause mortality compared to those living in moderate-high UV regions. Further studies are needed to determine the mechanisms underlying the UV index-mortality association.
authors.affiliation: Harold Simmons Center for Chronic Disease Research and Epidemiology, Division of Nephrology and Hypertension, University of California Irvine Medical Center, Orange, Calif., USA.
authors.forename: Bryan B
authors.initials: BB
authors.lastname: Shapiro
authors.forename: Elani
authors.initials: E
authors.lastname: Streja
authors.forename: Joline L T
authors.initials: JL
authors.lastname: Chen
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
authors.forename: Kamyar
authors.initials: K
authors.lastname: Kalantar-Zadeh
authors.forename: Connie M
authors.initials: CM
authors.lastname: Rhee
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000209:etiology* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D006435:Renal Dialysis / Q000401:mortality*; D016896:Treatment Outcome; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014481:United States