title: Dialysis dose and the effect of gender and body size on outcome in the HEMO Study.
abstract: BACKGROUND
  Gender and body size have been associated with survival in hemodialysis populations. In recent observational studies, overall mortality was similar in men and women and higher in small patients. The effect of dialysis dose in each of these subgroups has not been tested in a clinical trial.
  
  
  METHODS
  The HEMO Study was a controlled trial of dialysis dose and membrane flux in 1846 hemodialysis patients followed up for 6.6 years in 15 centers throughout the United States. We examined the effect of dialysis dose on mortality and on selected secondary outcomes in subgroups of patients.
  
  
  RESULTS
  Adjusting for age only, overall mortality was lower in patients with higher body weight (P < 0.001), higher body mass index (P < 0.001), and higher body water content determined by the Watson formula (Vw) (P < 0.001), but was not associated with gender (P= 0.27). The RR of mortality comparing the high dose with the standard dose group was related to gender (P= 0.014). Women randomized to the high dose had a lower mortality rate than women randomized to the standard dose (RR = 0.81, P= 0.02), while men randomized to the high dose had a nonsignificant trend for a higher mortality rate than men randomized to the standard dose (RR = 1.16, P= 0.16). Analysis of both genders combined showed no overall dose effect (R = 0.96, P= 0.52), as reported previously. Vw was greater than 35 L in 84% of men compared with 17% of women. However, the RR of mortality for the high versus standard dose remained lower in women than in men after adjustment for the interaction of dose with Vw or with other size parameters, including weight and body mass index. Conversely, the dose effect was not significantly related to size parameters after controlling for the relationship of the dose comparison with gender.
  
  
  CONCLUSIONS
  The data suggest that mortality and morbidity might be reduced by increasing the dialysis dose above the current standard in women but not in men. This effect was not explained by differences between men and women in age, race, or in several indices of body size. Because multiple comparisons were considered in this analysis, the role of gender on the effect of dialysis dose is suggestive and invites further study.
authors.affiliation: Division of Nephrology, University of California Davis, Sacramento, California 95817, USA. tadepner@ucdavis.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Depner
authors.forename: John
authors.initials: J
authors.lastname: Daugirdas
authors.forename: Tom
authors.initials: T
authors.lastname: Greene
authors.forename: Michael
authors.initials: M
authors.lastname: Allon
authors.forename: Gerald
authors.initials: G
authors.lastname: Beck
authors.forename: Cameron
authors.initials: C
authors.lastname: Chumlea
authors.forename: James
authors.initials: J
authors.lastname: Delmez
authors.forename: Frank
authors.initials: F
authors.lastname: Gotch
authors.forename: John
authors.initials: J
authors.lastname: Kusek
authors.forename: Nathan
authors.initials: N
authors.lastname: Levin
authors.forename: Edwin
authors.initials: E
authors.lastname: Macon
authors.forename: Edgar
authors.initials: E
authors.lastname: Milford
authors.forename: William
authors.initials: W
authors.lastname: Owen
authors.forename: Robert
authors.initials: R
authors.lastname: Star
authors.forename: Robert
authors.initials: R
authors.lastname: Toto
authors.forename: Garabed
authors.initials: G
authors.lastname: Eknoyan
mesh_terms: D044383:Black People; D001824:Body Constitution; D002423:Cause of Death; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000208:ethnology / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis; D012306:Risk; D012727:Sex Characteristics; D013997:Time Factors; D016896:Treatment Outcome