Dietary indices to measure diet quality in older cancer survivors: A scoping review on tools, their components and association with health outcomes

Background:
Older cancer survivors live with more comorbidities and have a higher mortality rate compared to the general older population. A high-quality diet that adheres to evidence based dietary recommendations and guidelines may help mitigate these issues. This can be assessed using dietary quality indices (DQIs), which objectively summarize scores for selected dietary components.

Objective:
Identify the DQIs available in the literature for older cancer survivors, and their associations with health outcomes.

Method:
Five databases were searched to identify peer-reviewed articles in English, from inception to 12th November 2024. Two researchers independently screened 3,145 studies, extracted and qualitatively assessed data from 28 included reports from 16 studies.

Results:
12 DQIs and 40 unique components within these indices were identified and summarised narratively. Total vegetables (n = 8), total fruits (n = 8), whole grains (n = 6), saturated fat (n = 8), and salt/sodium (n = 8) were the most frequently incorporated components within a DQI. All DQIs were derived from evidence-based dietary guidelines. Only three DQIs were specifically designed for oncology population. Higher diet quality was associated with higher HR-QoL in breast, prostate, and colorectal cancer survivors in all but one study. The associations between mortality and diet quality were inconsistent, depending on the type of cancer and the mortality type i.e., cancer-specific or other causes.

Conclusions:
DQIs are associated with important health outcomes. A major knowledge gap exists in DQIs suitable for older cancer survivors. Future research should develop DQIs to better assess how high-quality diets enhance health outcomes in older cancer survivors.