The paper is observational and although the authors adjust for known confounders the effect of residual confounding can’t be excluded. The other major limitations of the study acknowledged by the authors are that dialysis schedule was not directly ascertained but inferred indirectly from when the dose of dialysis was reported. Direct information about the dialysis schedule was not available. Therefore there is a possibility of measurement error. As well, information about death – the exact time, its relationship to dialysis schedule, and the fact that it occurred in hospital where the possibility that patients may not have been on their outpatient dialysis schedule raises concerns.
Nevertheless, despite these limitations, the study adds more weight to many other studies suggesting that our current way of dialyzing patients is simply not good enough. Here are a couple of paragraphs from the discussion in the paper:
“Despite its proven value as a life-saving therapy, HD [hemodialysis] remains an intermittent intervention, most typically administered three times a week. Harmful waste products and fluid accumulated over the extended weekend interval may therefore put patients at a higher risk of death on certain days. Our results from the DOPPS in the US, European, and Japanese patients indicate that, in all three regions, HD patients have a higher risk of all-cause death on Mondays if they are on a MWF schedule, or Tuesdays if they are on a TTS schedule. Thus, findings from prior reports are corroborated and expanded upon here. This day-of-week effect tends to be stronger for CVD than non-CVD death overall.”
They go on:
“Our results imply that there may be an advantage to a more frequent dialysis schedule in Europe, the United States, and potentially Japan. This is supported by the relatively low rates of mortality for patients receiving ‘daily dialysis’ based on various reports. One could hypothesize that more frequent dialysis would reduce or eliminate the day-of-week effect and, therefore, lower mortality on HD. Many previous reports have found that daily dialysis is beneficial.”
