To the Editor: Several methodological problems
could have influenced the outcome of the study by Dr Bliwise and colleagues.1 First, since this was not a randomized study, selection
bias is an important consideration. Factors that determine dialysis time have
an unknown effect on survival, including patient shift preference and shift
availability. Moreover, treatment time was recorded only twice, 1988 and 1991.
Twenty-four patients were excluded because their shift changed between 1988
and 1991. Additional determinations of dialysis time during the last 8 years
of the study would likely have excluded additional subjects.
Vassalotti JA. 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