For patients on maintenance hemodialysis, a new study, published in the Journal of Renal Nutrition, investigated the use of body mass index (BMI) and how changes to a patients’ BMI over time affected their prognosis, principally in relation to a decreased mortality risk.*

Background information

Chronic kidney disease (CKD) patients experiencing a rapid loss in kidney function, or acute kidney injury (AKI), or in stage 5 CKD will need dialysis or transplantation. There are two main types of dialysis: hemodialysis and peritoneal dialysis. In this particular study, only patients on hemodialysis formed part of the investigation.

Hemodialysis is a procedure that cleans the blood to remove waste products, including creatinine, extra fluid, potassium, and urea. The process lasts roughly four hours each time and is done three times a week if done at a dialysis center. Those undergoing hemodialysis at home will typically do the treatment more frequently but for a shorter amount of time each time. 

Your nephrologist will determine:

•  when hemodialysis is needed, 
• with what frequency (how many treatments per week), and 
• the length of each treatment.

These factors will all depend on how seriously a patient’s kidney is damaged, as well as on other health variables, such as BMI. BMI is a value derived from the mass (or weight) and height of an individual and allows one to classify a person as underweight (low BMI), normal weight, overweight (high BMI), or obese. A person’s BMI can be affected by a number of different factors, including, but not limited to, nutritional status, inflammation, and oxidative stress.

Research and investigation details

The researchers of this retrospective cohort study (a type of study that looks back at archived data) investigated the effect of changes in BMI on 187 patients doing both extended-hours hemodialysis and not following any dietary restrictions to ensure “sufficient nutrition.” They divided the patients into two groups based on changes in BMI between the third month and 12th month after they had transferred to the clinic.

Changes in BMI were measured over time, and the average follow-up time was 4.9 (3.0-8.6) years. Researchers examined the association between these variations in relation to all-cause mortality risk.

Results and conclusions

The authors of the study concluded that when patients on extended-hours hemodialysis had no dietary restrictions and their BMI maintained itself or increased, there was a decreased risk of mortality. This proved to be particularly noticeable in female patients aged 65 or older who did not have diabetic nephropathy (kidney damage due to Type 2, or diabetes mellitus (DM)).

*Hishida M., Imaizumi T., Nishiyama T., Okazaki M., et al. (2020, Mar. 1). “Survival Benefit of Maintained or Increased Body Mass Index in Patients Undergoing Extended-Hours Hemodialysis Without Dietary Restrictions.” Journal of Renal Nutrition.