Effect of Low-Fat Dietary Modification on Incident Open-Angle Glaucoma

We tested whether dietary modification (DM) altered the risk for incident primary open-angle glaucoma (POAG). Secondary analysis of a randomized intervention trial. We linked Medicare claims data to 45 203 women in the Women’s Health Initiative Dietary Modification Trial, of which 23 776 participants were enrolled in fee-for-service Medicare Part B and had physician claims. Women were randomized to follow either DM (a low-fat diet, with increased vegetable, fruit, and grain intake) or their usual diet without modification. Nine thousand three hundred forty women were randomized to the DM intervention, whereas 13 877 women were randomized to the control group. Our analyses were based on an intention-to-treat design, with a follow-up to the end of continuous Medicare coverage, death, or the last claims date (12/31/2018), whichever occurred first. Primary open-angle glaucoma was defined as the first claim with the International Classification of Diseases, Ninth or Tenth Revision, codes. Dietary data were assessed using a food frequency questionnaire. We used Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of POAG. Subgroup analyses were performed with P values for interaction. After exclusion of women with Medicare-derived glaucoma before randomization, the final analysis included 23 217 women (mean age, 64.4 ± 5.8 years). Baseline characteristics were balanced between the intervention and control groups. Primary open-angle glaucoma incidence was 11.1 per 1000 woman-years (mean follow-up, 11.6 ± 7.4 years; mean DM duration, 5.2 ± 3.2 years). We found no overall benefit of DM in reducing incident POAG (HR, 1.04; 95% CI, 0.96–1.12). Race and participant age did not modify this relation (P = 0.08 and P = 0.24 for interaction, respectively). In further analysis of baseline nutrient and food intake stratified by quartile groups, risk of open-angle glaucoma (OAG) in DM participants in the lowest quartile group for percentage calories (kilocalories) from total fat (33.8 or lower) was increased (HR, 1.22; 95% CI, 1.05–1.41; P = 0.007 for interaction). Analysis suggests that DM in participants in the lowest quartile group for percentage calories from total fat at baseline increased the risk of incident OAG among women regardless of age or race. Proprietary or commercial disclosure may be found after the references.