Risk Factor - Unhealthy Diet

Risk Factor - Sodium

Used in

Fruit, fiber, and legume intake is incorporated as a risk factor in the following disease models:

• CVD

Mechanism

Each dietary factor influences disease incidence through specific mechanisms and pathways:

• Low Fiber: Increases the risk of colorectal cancer, ischemic heart disease, stroke, and type 2 diabetes.
• Low Fruit: Increases the risk of ischemic heart disease, stroke and colorectal cancer.
• Low Legumes: Increases the risk of ischemic heart disease, stroke, and colorectal cancer.
• High Sodium: Increases blood pressure, which is a major risk factor for ischemic heart disease and stroke.

The model uses Relative Risks (RRs) and Population Attributable Fractions (PAFs), derived from epidemiological studies, to quantify these relationships:

• Relative Risk (RR): Indicates how much more likely someone with a particular dietary habit (e.g., low fiber intake) is to develop a specific disease compared to someone with a healthier habit (e.g., adequate fiber intake). The RR is often specific to a certain level of intake (e.g., per 200g/day increase in fruit).
• Population Attributable Fraction (PAF): Represents the proportion of disease incidence in the entire population that can be attributed to the specific dietary risk factor.

How the Model Calculates Changes (Intervention Impact):

The interventions aim to shift dietary intake towards healthier patterns. This leads to changes in PAFs and, consequently, disease incidence.

1. Baseline Intake: The model starts with a baseline level of intake for each dietary factor (fiber, fruit, legumes, sodium) for each age and sex group.

2. Intervention Impact: Each intervention is assigned an impact that represents how much it changes dietary intake.

   • Fiber: Front-of-pack labeling increases fiber intake by a specific amount (in grams per day).
   • Fruit & Legumes: Public procurement and mass media campaigns increase fruit and legume intake. The impact is often modeled as an increase in servings (e.g., 80g portions) per day.
   • Sodium:
     • Reformulation: Reduces sodium content in processed foods (absolute reduction in milligrams or grams per day).
     • Front-of-pack labeling: Reduces sodium intake by influencing consumer choices (often modeled as a percentage reduction).
     • Knowledge/Education: Reduces sodium intake through behavior change (absolute reduction).
     • Salt Reduction in Environment: Reduces sodium by restricting salt availability.

3. Coverage: The model considers the coverage of each intervention - the percentage of the target population reached.

4. Calculating Overall Intake Change: The model combines the impacts and coverage of the interventions to determine the overall change in dietary intake for each factor.

5. Calculating PAF Adjustment: After calculating the changes in dietary intake, the model recalculates the Population Attributable Fractions (PAFs) based on the new consumption levels. The model uses the dose-response relationships from epidemiological studies to determine how changes in intake translate to changes in disease risk. For example, for every 200g increase in fruit intake, the model applies the corresponding risk reduction based on the relative risk values. The PAF represents how much of the disease burden can be attributed to the current dietary pattern, and it decreases when intake patterns improve.

Specific Mechanisms and Examples:

• Fiber, Fruit, and Legumes: The model uses a "per unit change" approach for these. For example:

  • Fruit: The RR for ischemic heart disease is 0.92 per 200g/day increase in fruit intake. This means that for every 200g increase in daily fruit consumption, the risk of IHD is reduced by 8% (1 - 0.92 = 0.08). The interventions aim to increase fruit intake, and the model calculates the corresponding reduction in risk based on this "per 200g" RR.
  • Fiber: The RR for ischemic heart disease is 0.81 per 8g/day increase in fiber intake. Interventions increase fiber intake, and the model calculates the risk reduction based on this "per 8g" RR.

• Sodium and Blood Pressure: The sodium interventions have a two-step effect:

  1. Reduced Sodium Intake: Interventions reduce sodium intake (either absolutely or relatively).
  2. Reduced Blood Pressure: The reduced sodium intake leads to a reduction in mean systolic blood pressure (SBP) in the population. The model uses a coefficient (derived from research) that links sodium reduction to SBP reduction (e.g., a certain reduction in mmol of sodium leads to a specific reduction in mmHg of SBP).
  3. Reduced Risk of IHD and Stroke: The reduction in SBP, in turn, leads to a reduced risk of ischemic heart disease and stroke. The model uses RRs that link SBP levels to the risk of these diseases.

  This indirect pathway (sodium -> blood pressure -> IHD/stroke) is crucial for modeling the impact of sodium reduction. The model accounts for this by updating the PAFs for IHD and stroke based on the change in SBP caused by the change in sodium intake.

In Summary

The model simulates the impact of dietary interventions by:

• Changing the intake levels of fiber, fruit, legumes, and sodium.
• These changes in intake lead to changes in Population Attributable Fractions (PAFs) for related diseases.
• For sodium, the model explicitly includes the intermediate step of blood pressure reduction.
• The adjusted PAFs, in turn, lead to changes in incidence rates for the associated NCDs.

Interventions

Intervention Table

This document describes how the model addresses dietary risk factors, specifically focusing on unhealthy diet components including low intake of fiber, fruits, and legumes, as well as high sodium intake. These dietary factors are linked to various non-communicable diseases (NCDs).

U1

U2

U3

U4

U6

U7

U10

U11

Assumptions

Relative Risks

References for relative risks come from

• Micha 2018
• Reynolds et al. 2019

Sodium intake (g/day)

Fiber intake (g/day)

Fruit intake (g/day)

Legume intake (g/day)

Impact on Prevalence

Data Viewer

Below is a CSV viewer showing the fruit, fiber, and legumes data files used in this model: