Abstract Body (Do not enter title and authors here): Background/Introduction: Dietary micronutrient insufficiencies, which are common in patients with heart failure (HF) and linked to event-free survival (time to hospitalization or death), often result from monotonous diets. Thus, diet monotony, dietary micronutrient insufficiencies, and time to hospitalization or death are likely to be interrelated. Understanding this relationship will help design evidence-based interventions to promote diet quality and improve survival in patients with HF.

Aim: To determine if dietary micronutrient insufficiency mediates the relationship of diet monotony with time to hospitalization or death.

Methods: A total of 245 patients with HF (61 ± 12 years old, 66% male) were included from a prospective observational study. From a four-day food diary, diet monotony was measured using diet variety scores calculated from 23 food types consumed. Higher diet variety scores indicate less monotonous diets. Dietary micronutrient insufficiency was defined as the number of dietary insufficiencies of 17 vitamins and minerals. A linear regression and a Cox Proportional Hazards model were used to confirm the mediating effect of dietary micronutrient insufficiency on time to hospitalization or death in year 1, adjusting for covariates.

Results: We found an estimated increase in median survival, 30.54 (Total effect; 95% CI= - 0.50, 53.15; p=.051) days due to diet variety, with an estimated increase of 18.15 (95% CI= 1.52, 62.25; p=.021) days (Average causal mediation effect) as a result of the dietary micronutrient insufficiency. The remaining 12.39 (95% CI= - 53.09, 35.19; p=.27) days were from diet variety alone. Having a less monotonous diet was significantly associated with decreased dietary micronutrient insufficiency (a= - 0.38; 95% CI= - 0.53, - 0.22). Increased dietary micronutrient insufficiency was significantly associated with reduced time to hospitalization or death (b = - 0.11; 95% CI= - 0.21, - 0.02), controlling for covariates. Thirty-eight percent of the effect of diet monotony on time to hospitalization or death went through dietary micronutrient insufficiency.

Conclusions: A more monotonous diet was positively associated with a higher number of dietary micronutrient insufficiencies, leading to a shorter time to hospitalization or death. Future nutrition counseling interventions should consider promoting a variety of foods to reduce dietary micronutrient insufficiency and improve survival outcomes among patients with HF.