Dialysis Gender Gap May Correlate With Hospitalizations, Mortality Risk
Studies show that in the general population women tend to have better health and greater longevity than men. In the maintenance hemodialysis patient population, however, the opposite is true. In fact, female dialysis patients (regardless of race, ethnicity, diabetic status and other comorbidities) have a higher mortality risk, a 21% higher hospitalization rate, and are more likely to be readmitted to the hospital within 30 days compared with male dialysis patients. While the 1.7-to-2.1 hospitalization variance is not extreme, it is significant enough to warrant a look at how dialysis may play a part in this discrepancy.
Hypothesis: Women receive less dialysis than assumed
It stands to reason that female dialysis patients’ lesser health could be related to lower overall small molecule solute clearance, leaving fluid and toxins to accumulate and cause the issues prompting hospitalization. Assuming this, why would standard dialysis treatments produce subpar outcomes for women compared with men? One theory suggests the standard Kt/V urea measurement for dialysis may be at the crux of the matter.
Because the traditional Kt/V urea measurement is based on volume, it serves as an accurate measure—and thus dosage guide—for men but not necessarily for women. Consider the surface area and volume differences between women and men. Due to their generally smaller size, women have a higher surface-area-to-volume ratio. Research using surface area to standardize Kt/V has shown that women are under-dosed using the Kt/V guide and thus, receive less dialysis. At this time, however, surface-area-normalized Kt/V is not standard for clearance measurement and dosing guidance, and is only used in research settings.
In addition to surface-area normalized Kt/V, nutritional status measures may also indicate women receive less dialysis than their male counterparts. When researchers looked at serum albumin levels of men and women on dialysis, women had distinctly lower levels. Is there a link between low clearance and lower albumin levels? Ample data shows a correlation between low clearance and a lower normalized catabolic protein rate (nPCR), as well as a correlation between lower nPCR and lower albumin levels—suggesting a possible connection. However, serum albumin concentration depends on more than small molecule solute clearance; protein intake, liver health, inflammation, and proteinuria all affect and add to complexities of serum albumin analysis.
Without definitive research, inadequate dialysis cannot be named as the causative agent behind higher hospitalizations and mortality risk among female dialysis patients. However, the aforementioned considerations suggest the standard dosing system based on volume may underdose about half of the dialysis patient population, specifically women. Additional research is needed to determine if clearance measurement/dosage guides require modification for women, and could produce better outcomes, fewer hospitalizations, and lower mortality.