Carbohydrate nutrition, glycemic index, and the 10-y incidence of cataract.

BACKGROUND

Although dietary carbohydrates are thought to play a role in cataractogenesis, few epidemiologic studies have examined links between carbohydrate nutrition and cataract.

OBJECTIVE

We investigated the associations between dietary glycemic index (GI), glycemic load (GL), total carbohydrate intake, and 10-y incident nuclear, cortical, and posterior subcapsular cataract.

METHODS

Of 3654 baseline participants in an Australian population aged >/=49 y (1992-1994), 933 were seen after 5 and/or 10 y, had completed a detailed semiquantitative food-frequency questionnaire, had no previous cataract surgery or baseline cataract, and had photographs taken to assess incident cataract with the Wisconsin Cataract Grading System. Dietary information was collected with a validated food questionnaire. GI was calculated from a customized database of Australian foods. GI, GL, and all other nutrients were energy adjusted. Hazard ratios (HRs) and 95% CIs were calculated with the use of discrete logistic models.

RESULTS

After age, sex, diabetes, and other factors were controlled for, each SD increase in GI significantly predicted incident cortical cataract (HR: 1.19; 95% CI: 1.01, 1.39). Participants within the highest compared with the lowest quartile of GI were more likely to develop incident cortical cataract (HR: 1.77; 95% CI: 1.13, 2.78; P for trend = 0.035). These findings were similar after excluding participants with diabetes, although they were slightly attenuated and marginally nonsignificant (HR: 1.16; 95% CI: 0.98, 1.37, per SD increase in GI). No association was found between GI and nuclear or posterior subcapsular cataract and between GL or carbohydrate quantity and any cataract subtype.

CONCLUSIONS

In an Australian cohort, poorer dietary carbohydrate quality, reflected by high GI, predicted incident cortical cataract.