Mortality and Dietary Patterns in Patients on Hemodialysis

Patients with end-stage renal disease are at high risk for premature death. On average, life expectancy among patients who initiate long-term hemodialysis therapy is 3 to 4 years; cardiovascular disease is responsible for approximately 40% of those deaths. Compared with findings in the general population, there are only minimal or no survival benefits associated with interventions designed to lower lipid levels, control blood pressure and glucose levels, and prevent thrombosis in patients in maintenance dialysis therapy. Identification of strategies to prevent cardiovascular death is a priority for patients, caregivers, and clinicians.

Clinical practice guidelines for dietary intake among hemodialysis patients to control serum phosphate and potassium levels and fluid overload while maintaining high intake of protein and energy focus on individual nutrients. There are few data available on the association between dietary patterns and cardiovascular and all-cause mortality in adults treated by hemodialysis.

Valeria M. Saglimbene, MScMed, and colleagues conducted a secondary analysis of data from  the DIET-HD (Dietary Intake Death and Hospitalization in Adults with End-State Kidney Dieseae Treated with Hemodialysis) study to generate data-driven patterns reflecting the eating behavior of patients in the DIET-HD hemodialysis cohort. The researchers sought to examine the association between commonly practiced dietary patterns and cardiovascular and all-cause mortality in that patient population. Results of the prospective cohort study were reported in the American Journal of Kidney Diseases [2020;75(3):361-372].

Eligible patients completed the Global Allergy and Asthma European Network food frequency questionnaire (FFQ) during a routine hemodialysis treatment, either independently or assisted by an interviewer in the case of severe clinical conditions or limited literacy. The FFQ is an internationally validated instrument to ascertain dietary intake to facilitate international comparisons. The FFQ records the consumption of 210 foods during the previous 12 months, at frequencies ranging from never to four or more times per day; FFQ responses were converted into average servings per week.

Energy intake was estimated from food intake considering standard portion size and using the latest available McCance & Widdowson’s Food Composition Tables. Patients with more than 20% missing answers or implausible responses were excluded from the data analyses.

A total of 9757 hemodialysis patients completed the FFQ between January 2014 and January 2015. Of those, 8110 had complete and plausible dietary data and were followed-up through June 27, 2017. At baseline, mean age of the cohort was 63 years, 58% were men, 68% had a life partner, 44% had secondary education; 15% reported daily physical activity, and 18% were wait-listed for a kidney transplant. Thirty-three percent were current or former smokers, 5% were underweight, 42% had normal weight, 34% were preobese, and 20% were obese; 85% had hypertension, 32% had diabetes, 12% had experienced a myocardial infarction, and 9% had experienced stroke.

Of the 210 food items in the FFQ, 179 were included in the principal component analysis; exclusion of the 31 food items was due to infrequent consumption. The first dietary pattern identified was characterized by higher intake of fruit (including stone, citrus, and pome [pears and apples] fruit) and vegetables (including cruciferous and green leafy vegetables). The second pattern was characterized by higher intake of Western-style foods, such as French fries, other potato meals, eggs, desserts, red and processed meat (including bacon, sausages, beef burger, and meat pie), fish (mostly cured, smoked, or tinned), and pizza. Higher levels of both dietary pattern scores in quartiles were associated with higher total energy intake. Both dietary patterns were consistently seen across the 11 countries in the study. The patterns were identified as (1) fruit and vegetables and (2) Western.

Participants received a score for each identified pattern, with higher scores indicating closer resemblance of their diet to the identified pattern. Quartiles of standardized pattern scores were used as primary exposures.

Median follow-up was 2.7 years (18,666 person-years). During the follow-up period, there were 2087 deaths; 958 of those were attributable to cardiovascular diseases.

In multivariable analyses, compared with patients in the lowest quartile of the fruit and vegetable dietary pattern score, adjusted hazard ratios for cardiovascular mortality in the other quartiles, in ascending order, were 0.94 (95% confidence interval [CI], 0.76-1.15), 0.83 (95% CI, 0.66-1.06), and 0.91 (95% CI, 0.69-1.21). For the Western dietary pattern, the corresponding estimates were 1.10 (95% CI, 0.90-1.35), 1.11 (95% CI, 0.87-1.41), and 1.09 (95% CI, 0.80-1.49). Findings were similar in case-complete analyses. The results of continuous dietary patterns scores agreed with those of quartiles.

In adjusted analyses of all-cause mortality, compared with patients in the lowest quartile of the fruit and vegetable dietary pattern score, hazard ratios among patients in the other quartiles, in ascending order, were 0.95 (95% CI, 0.83-1.09), 0.84 (95% CI, 0.71-0.99). and 0.87 (95% CI, 0.72-1.05). For the Western dietary pattern, corresponding estimates were 1.01 (95% CI, 0.88-1.16), 1.00 (95% CI, 0.85-1.18), and 1.14 (95% CI, 0.93-1.41). Results of case-complete analyses were similar. With the exception of a significant association between higher fruit and vegetables dietary pattern score and lower all-cause mortality in case-complete analysis, results of continuous dietary patterns scores agreed with those of quartiles.

Study limitations cited by the authors included the use of the self-reported food frequency questionnaire and the possibility that the data-driven approach could limit the generalizability of the findings to patients living outside of Europe and Argentina.

“In conclusion, our findings did not confirm an association between mortality among patients receiving long-term hemodialysis and the extent to which dietary patterns were either high in fruit and vegetables or consistent with a Western diet. Trials investigating the benefits and harms of more inclusive diets are warranted,” the researchers said.

Takeaway Points

1. Researchers conducted an analysis of data from the DIET-HD study to examine the associations between dietary patterns and cardiovascular and all-cause mortality in a cohort of adults on long-term hemodialysis.
2. The prospective cohort study included 8100 patients on hemodialysis from January 2014 to January 2015; follow-up continued until June 27, 2017.
3. There was no association between mortality in the patient population and the extent to which dietary patterns were either high in fruit and vegetables or consistent with a Western diet.