Hemodialysis (HD) patients who dialyze for shorter periods are at increased risk of death compared with those who have longer dialysis sessions, regardless of their body weight, data suggest.
Researchers at Brigham and Women’s Hospital in Boston compared 2,382 HD patients whose prescribed dialysis session length (DSL) was 240 minutes or more with a matched cohort of 2,382 HD patients whose prescribed DSL was less than 240 minutes. All patients received in-center, three-times-weekly HD and had adequate urea clearance. Investigators selected patients at random from dialysis facilities across a diverse geographic distribution in the United States.
After controlling for differences in body weight and other potential confounders, patients who dialyzed for less than 240 minutes had a significant 26% increased risk of all-cause mortality compared with those who dialyzed for more than 240 minutes, according to an online report in Kidney International. The association was consistent across strata of age, gender, and dialysis post-weight.
In addition, compared with a DSL of 240 minutes or more, the risk of death increased with decreasing DSL: a DSL of 210-239 minutes was associated with a 28% increased risk and a DSL less than 210 minutes was associated with a 30% increased risk.
The investigators, led by Jennifer E. Flythe, MD, noted that ultrafiltration rates were higher among the shorter DSL patients than the longer DSL patients, even though the longer DSL group had greater interdialytic weight gain. Previous studies suggest that higher ultrafiltration rates are associated with increased all-cause and cardiovascular mortality, the authors observed. They explained that shorter DSL implies less time for fluid removal and thus higher ultrafiltration rates. This could explain, in part, the association between shorter DSL and increased death risk, according to the investigators.
In their discussion of study strengths, the researchers noted that they had a large, nationally representative cohort, used standardized protocols for data collection across HD units, and used tight matching parameters to create strict control over the most influential confounders. As for study limitations, the authors noted that they relied on observational data, which has an inherent risk for uncontrolled confounding.