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March 13, 2002

Does Time of Day of Hemodialysis Affect Survival?

JAMA. 2002;287(10):1262-1264. doi:10-1001/pubs.JAMA-ISSN-0098-7484-287-10-jlt0313

To the Editor: Dr Bliwise and colleagues1 report an association between time of day of hemodialysis in an elderly cohort of patients with ESRD. It is possible, however, that the difference in survival between shifts may be even larger than they reported. The morning cohort had a greater body mass index (BMI). The median dialysis times between the groups were similar, however, suggesting that the morning patients likely received a lower dose of hemodialysis. Lower doses of hemodialysis have been associated with increased mortality.2 Such a trend within this cohort would bias the results toward the null hypothesis that no difference exists between the groups. Likewise, there was a higher percentage of black patients in the morning group. Given that black patients with ESRD tend to have lower hemoglobin values than do white dialysis patients3 and that lower hemoglobin predicts mortality in ESRD,4 bias would again be introduced toward the null hypothesis. In an adjusted model, such differences would widen the disparity in mortality between shifts.