Effect of Age and Dialysis Vintage on Obesity Paradox in Long-term Hemodialysis Patients

• Published in: American journal of kidney diseases Vol. 63; no. 4; pp. 612 - 622
• Main Authors: Vashistha, Tania, MD, Mehrotra, Rajnish, MD, Park, Jongha, MD, Streja, Elani, MPH, PhD, Dukkipati, Ramnath, MD, Nissenson, Allen R., MD, Ma, Jennie Z., PhD, Kovesdy, Csaba P., MD, Kalantar-Zadeh, Kamyar, MD, MPH, PhD
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.04.2014; Elsevier
• Subjects: Age Factors; Aged; Biological and medical sciences; BMI; Body Mass Index; Cardiovascular Diseases - mortality; Cardiovascular Diseases - physiopathology; ESRD; Female; hemodialysis; Humans; Kidney Failure, Chronic - epidemiology; Kidney Failure, Chronic - mortality; Kidney Failure, Chronic - therapy; Male; Medical sciences; Metabolic diseases; Middle Aged; mortality risk; Nephrology; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Obesity; Obesity - epidemiology; Obesity - mortality; Obesity - physiopathology; Obesity-mortality paradox; Renal Dialysis - mortality; Renal failure; Retrospective Studies; Survival Analysis; ESRD; hemodialysis; Obesity-mortality paradox; mortality risk; BMI; Kidney disease; Human; Obesity; Nephrology; Urinary system disease; Chronic renal failure; Hemodialysis; Mortality; Nutrition disorder; Terminal stage; Epidemiology; Long term; Urology; Extrarenal dialysis; Body mass index; Risk factor; Dialysis; Age; Nutritional status
• ISSN: 0272-6386; 1523-6838
• DOI: 10.1053/j.ajkd.2013.07.021

Background In contrast to the general population, higher body mass index (BMI) is associated with greater survival in patients receiving hemodialysis (HD; “obesity paradox”). We hypothesized that this paradoxical association between BMI and death may be modified by age and dialysis vintage. Study Design Retrospective observational study using a large HD patient cohort. Setting & Participants 123,383 maintenance HD patients treated in DaVita dialysis clinics between July 1, 2001, and June 30, 2006, with follow-up through September 30, 2009. Predictors Age, dialysis vintage, and time-averaged BMI. Time-averaged BMI was divided into 6 subgroups; <18.5, 18.5-<23.0, 23.0-<25.0, 25.0-<30.0, 30.0-<35.0, and ≥35.0 kg/m2 . BMI category of 23-<25 kg/m2 was used as the reference category. Outcomes All-cause, cardiovascular, and infection-related mortality. Results Mean BMI of study participants was 27 ± 7 kg/m2 . Time-averaged BMI was <18.5 and ≥35 kg/m2 in 5% and 11% of patients, respectively. With progressively higher time-averaged BMI, there was progressively lower all-cause, cardiovascular, and infection-related mortality in patients younger than 65 years. In those 65 years or older, even though overweight/obese patients had lower mortality compared with underweight/normal-weight patients, sequential increases in time-averaged BMI > 25 kg/m2 added no additional benefit. Based on dialysis vintage, incident HD patients had greater all-cause and cardiovascular survival benefit with a higher time-averaged BMI compared with the longer term HD patients. Limitations Causality cannot be determined, and residual confounding cannot be excluded given the observational study design. Conclusions Higher BMI is associated with lower death risk across all age and dialysis vintage groups. This benefit is more pronounced in incident HD patients and those younger than 65 years. Given the robustness of the survival advantage of higher BMI, examining interventions to maintain or even increase dry weight in HD patients irrespective of age and vintage are warranted.