Model-based estimation of the generalized impact fraction (GIF) and population attributable fraction (PAF) for interventions targeting risk factors affecting the five-year risk of diabetic retinopathy.

BACKGROUND

Diabetic Retinopathy (DR) is a microvascular complication of diabetes mellitus. Health policymakers are interested in studying the impact of interventions on reducing new cases of DR. The study aimed to calculate the generalized impact fraction (GIF) and population attributable fraction (PAF) of interventions targeting three risk factors on the five-year risk of DR.

METHODS

A retrospective cohort study was conducted among 1,742 patients with diabetes who completed their baseline assessment between 2015 and 2017. Follow-up studies were carried out during visits from 2020 to 2022, aiming to determine the five-year risk of DR. To estimate the PAF and GIF in different scenarios, a parametric G. formula was utilized.

RESULTS

In this study, all patients had type 2 diabetes, and the five-year risk of developing diabetic retinopathy (DR) was 16.1% (95% CI: 14.4-18.0). Lowering HbA1c to below 7% would be expected to prevent 35.07% (95% CI: 34.7-36.2) of DR cases. A reduction of 30% in patients with HbA1c levels above 7% corresponds to a GIF of 10.3% (95% CI: 9.9-10.7). Similarly, normalizing blood pressure levels resulted in a PAF of 22.1% (95% CI: 21.8-22.6). A 25% decrease in prevalence above 130/80 mmHg was associated with a GIF for DR of 5.3% (95% CI: 5.1-5.4). Reducing LDL cholesterol levels to less than 100 mg/dl had a lower impact, with a PAF of 1.9% (95% CI: 1.3-2.3). A 20% reduction in prevalence above this level corresponded to a GIF of 0.3% (95% CI: 0.2-0.5).

CONCLUSION

Reducing HbA1c and blood pressure by 20-30% would be expected to prevent the five-year risk of DR by 15.5% (95% CI: 15.3-15.9). These levels of decrease are achievable and conceivable to policymakers, which can encourage them to implement a program. This could be a Policy-making approach to prevent DR.