Lean Body Mass Linked to Better Mental Health, Survival in Dialysis Patients

Lean Body Mass Linked to Better Mental Health, Survival in Dialysis Patients

Laurie Barclay, MD

October 15, 2010 — Higher midarm muscle circumference (MAMC) is a marker for larger lean body mass (LBM) and an independent predictor of better mental health and greater survival in patients receiving maintenance hemodialysis (MHD), according to the results of a study reported online October 14 in the Clinical Journal of the American Society of Nephrology.

"[Patients receiving MHD] with larger body or fat mass have greater survival than [those with] normal to low mass," write Nazanin Noori, MD, PhD, from Harold Simmons Center for Chronic Disease Research and Epidemiology and Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor–University of California–Los Angeles Medical Center in Torrance, and colleagues. "We hypothesized that [MAMC], a conveniently measured surrogate of [LBM], has stronger association with clinical outcomes than triceps skinfold (TSF), a surrogate of fat mass."

In this study, 792 patients receiving MHD underwent measurements of TSF, MAMC, and serum creatinine as another marker for LBM. The investigators studied the associations of these measurements with baseline Short Form 36 quality-of-life scores and 5-year survival. LBM was measured by dual-energy X-ray absorptiometry in a randomly selected subsample of 118 participants.

LBM was most strongly correlated with MAMC and serum creatinine. After adjustment for case mix, malnutrition-inflammation-cachexia syndrome, and inflammatory markers, higher MAMC was associated with better hazard ratio (HR) for the Short Form 36 mental health scale and lower HR for death. For the first to fourth MAMC quartiles, adjusted death HRs were 1.00, 0.86, 0.69, and 0.63.

Although higher serum creatinine and TSF were also associated with lower HRs for death, these associations were attenuated after multivariate adjustments. Survival was greatest with combined high MAMC with either high or low TSF (vs low MAMC/TSF) when median values of TSF and MAMC were used to dichotomize. HRs for death were 0.52 and 0.59, respectively.

"Higher MAMC is a surrogate of larger LBM and an independent predictor of better mental health and greater survival in MHD patients," the study authors write. "Sarcopenia-correcting interventions to improve clinical outcomes in this patient population warrant controlled trials."

Limitations of this study include possible selection bias during enrollment, lack of detailed information about hemodialysis treatment and technique, use of skinfold measurements quantifying peripheral rather than central fat tissue, and observational design with possible unmeasured or residual confounding.

"It is possible that interventions that can improve muscle mass or increase lean body mass can lead to better clinical outcomes and greater survival in tens of thousands of dialysis patients and probably millions of individuals with other stages of chronic kidney disease or other chronic disease states," senior author Kamyar Kalantar-Zadeh, MD, PhD, from the University of California–Los Angeles School of Public Health, said in a news release.

In an accompanying editorial, Kirsten L. Johansen, MD, from the San Francisco VA Medical Center in California, notes that both body fat and muscle mass are correlated with survival among patients who are receiving HD.

"Certainly, one could argue that anthropometry is not a perfect means of measuring body composition in the dialysis population, [but] it seems unlikely that TSF and MAMC are so flawed as to produce false associations," Dr. Johansen writes. "On the basis of these studies, we can be relatively confident that the association of high [body mass index] with improved survival among HD patients is more complex than a simple association with greater body fat. The next challenge will be to address the mechanisms underlying the associations between body composition and survival so that we can consider strategies to change body composition and determine whether such intervention can improve outcomes, and this challenge may require more precise measures of body composition than [body mass index] or anthropometry."

The National Institutes of Health, DaVita Clinical Research, Mr. Harold Simmons, and the National Center for Research Resources supported this study. The study authors and Dr. Johansen have disclosed no relevant financial relationships.

Clin J Am Soc Nephrol. Published online October 14, 2010.

http://www.medscape.com/viewarticle/730628