Washington, DC (April 24, 2014) -- Dialysis patients with more muscle mass had better scores on a 6-minute walking test as well as better scores on physical and mental health questionnaires in a study appearing in an upcoming issue of the Clinical Journal of the American Society of Nephrology (CJASN). The findings suggest that physical activity that builds muscle mass may help improve the health and quality of life of dialysis patients.

Physical functional ability is often significantly impaired in patients on maintenance hemodialysis. Srinivasan Beddhu, MD (University of Utah), Macy Martinson, MD (University of Utah), T. Alp Ikizler (Vanderbilt University), and their colleagues wondered whether modifiable factors such as body size and body composition could influence dialysis patients' physical function and quality of life.

To investigate, the researchers assessed 105 maintenance dialysis patients' body mass index (BMI), waist circumference, and measurements of mid-thigh muscle area and intra-abdominal fat area. They also tested how far patients could walk in 6 minutes, and they examined other measures of physical and mental health through questionnaires. Assessments were made at the start of the study, after 6 months, and after 12 months.

The investigators found that higher BMI levels at the start of the study were linked with shorter 6-minute walking distances measured at both at the start of the study and at later time points. Results were similar for waist circumference and intra-abdominal fat. On the other hand, higher levels of mid-thigh muscle--which indicates higher muscle mass--were linked with longer 6-minute walking distances. After adjusting for BMI, increases in mid-thigh muscle were also strongly linked with higher physical and mental health scores at the start of the study, but only weakly so at later time points.

"Because this study shows that higher muscle mass is associated with better physical function and quality of life in dialysis patients, interventions such as increased physical activity that decrease fat mass and increase muscle mass are likely to improve physical function, quality of life, and survival in dialysis patients," said Dr. Beddhu. "Such interventions need to be tested in clinical trials."

The findings may help explain the "obesity paradox" associated with dialysis patients, which relates to the prolonged survival sometimes seen in obese patients compared with normal-weight patients. "The obesity paradox has been interpreted in earlier studies as fat is good. Some have even argued that weight loss should be discouraged in dialysis patients," said Dr. Beddhu. "But the situation is more nuanced. This study provides a better understanding of the role of body composition in dialysis patients."

###

Highlights

Dialysis patients with higher BMI, waist circumference, and abdominal fat measures had poorer scores on a 6-minute walking test.

Patients with more muscle mass had better scores on the walking test as well as better scores on physical and mental health questionnaires. Worldwide, more than 1.5 million people are treated with hemodialysis.

Study co-authors include T. Alp Ikizler,MD, Glen Morrell, MD, PHD, Guo Wei, Nestor Almeida, MD, Robin Marcus, PT, PhD, Rebecca Filipowicz, and Tom Greene, PhD.

Disclosures: The authors reported no financial disclosures.

The article, entitled "Associations of Body Size and Body Composition with Functional Ability and Quality of Life in Hemodialysis Patients," will appear online at http://cjasn. asnjournals. org/ on April 24, 2014.

The content of this article does not reflect the views or opinions of The American Society of Nephrology (ASN). Responsibility for the information and views expressed therein lies entirely with the author(s). ASN does not offer medical advice. All content in ASN publications is for informational purposes only, and is not intended to cover all possible uses, directions, precautions, drug interactions, or adverse effects. This content should not be used during a medical emergency or for the diagnosis or treatment of any medical condition. Please consult your doctor or other qualified health care provider if you have any questions about a medical condition, or before taking any drug, changing your diet or commencing or discontinuing any course of treatment. Do not ignore or delay obtaining professional medical advice because of information accessed through ASN. Call 911 or your doctor for all medical emergencies.

Founded in 1966, and with more than 14,000 members, the American Society of Nephrology (ASN) leads the fight against kidney disease by educating health professionals, sharing new knowledge, advancing research, and advocating the highest quality care for patients.