Dietary omega-3 fatty acid, ratio of omega-6 to omega-3 intake, inflammation, and survival in long-term hemodialysis patients

Background: 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.

Study design: Prospective cohort study using linear and Cox proportional regressions.

Setting & participants: 145 hemodialysis patients from 8 DaVita dialysis clinics in Southern California in 2001-2007.

Predictors: Intake of dietary omega-3 and ratio of omega-6 to omega-3 using 3-day food record supplemented by dietary interview.

Outcomes: 1-year change in serum C-reactive protein (CRP) level and 6-year survival.

Results: 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).

Limitations: 3-day food record may underestimate actual dietary fat intake at an individual level.

Conclusions: 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.