Abstract
Mortality in long-term hemodialysis patients is high, mostly attributed to cardiovascular events, and may be related to chronic inflammation. We hypothesized that the anti-inflammatory benefits of higher dietary intake of omega-3 compared with omega-6 polyunsaturated fatty acids may modulate the inflammatory processes and decrease death risk. Prospective cohort study using linear and Cox proportional regressions. 145 hemodialysis patients from 8 DaVita dialysis clinics in Southern California in 2001-2007. Intake of dietary omega-3 and ratio of omega-6 to omega-3 using 3-day food record supplemented by dietary interview. 1-year change in serum C-reactive protein (CRP) level and 6-year survival. Patients were aged 53 ± 14 years (mean ± SD) and included 43% women and 42% African Americans. Median dietary omega-3 intake, ratio of omega-6 to omega-3 intake, baseline serum CRP level, and change in CRP level over 1 year were 1.1 (25th-75th percentile, 0.8-1.6) g/d, 9.3 (25th-75th percentile, 7.6-11.3), 3.1 (25th-75th percentile, 0.8-6.8) mg/L, and +0.2 (25th-75th percentile, -0.4 to +0.8) mg/L, respectively. In regression models adjusted for case-mix, dietary calorie and fat intake, body mass index, and history of hypertension, each 1-unit higher ratio of omega-6 to omega-3 intake was associated with a 0.55-mg/L increase in serum CRP level (P = 0.03). In the fully adjusted model, death HRs for the first (1.7-<7.6), second (7.6-<9.3), third (9.3-<11.3), and fourth (11.3-17.4) quartiles of dietary omega-6 to omega-3 ratio were 0.39 (95% CI, 0.14-1.18), 0.30 (95% CI, 0.09-0.99), 0.67 (95% CI, 0.25-1.79), and 1.00 (reference), respectively (P for trend = 0.06). 3-day food record may underestimate actual dietary fat intake at an individual level. Higher dietary omega-6 to omega-3 ratio appears to be associated with both worsening inflammation over time and a trend toward higher death risk in hemodialysis patients. Additional studies including interventional trials are needed to examine the association of dietary fatty acids with clinical outcomes in these patients.
Highlights
MethodsPatient PopulationWe studied maintenance HD patients who participated in the NIH-funded NIED (Nutritional and Inflammatory Evaluation in Dialysis) Study.[15,16,17,18,19,20,21,22] The original patient cohort was derived from a pool of approximately 1,300 maintenance HD outpatients in eight DaVita dialysis clinics from the South Bay Los Angeles area
Mortality among long-term hemodialysis patients is high, mostly attributed to cardiovascular events, and may be related to chronic inflammation
Higher dietary omega-6 to omega-3 ratio appears associated with both worsening inflammation over time and a trend towards higher death risk in hemodialysis patients
Summary
Patient PopulationWe studied maintenance HD patients who participated in the NIH-funded NIED (Nutritional and Inflammatory Evaluation in Dialysis) Study.[15,16,17,18,19,20,21,22] The original patient cohort was derived from a pool of approximately 1,300 maintenance HD outpatients in eight DaVita dialysis clinics from the South Bay Los Angeles area. Dietary intakes of 145 randomly selected patients were assessed with a 3-day dietary record, accompanied by a diet interview, during the first 6 months of the study (see below). These 145 patients were followed for up to 72 months, i.e. until September 30, 2007. Cox-regressionbased restricted cubic splines graph with two degrees of freedom were employed to illustrate systematic relations between dietary intakes and mortality This method served to examine the non-linear associations as continuous mortality predictors as an alternative to potential inappropriate assumptions concerning linearity.[34] Death hazard ratios were obtained using Cox proportional hazard models after controlling for covariates. Descriptive and multivariate statistics were carried out with the statistical software Stata (version 10.0; Stata Corporation, www.stata.com)
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