Abstract
Purpose: :
To assess the pattern of association between baseline fasting blood glucose level and the long-term incidence and progression of the 3 major types of cataract.
Methods: :
3654 persons aged 49+ years were examined at baseline and 2454 were re-examined after 5 and/or 10 years. Lens photographs were taken at each visit and graded using the Wisconsin Cataract Grading system. Incident cataract was defined as the appearance of nuclear, cortical or posterior subcapsular (PSC) cataract subtypes in bilaterally phakic participants who did not have the corresponding cataract subtype at baseline. Progression of cortical and PSC cataract was defined as an increase by at least 10% and 2% respectively, in the lens area affected by the corresponding cataract. Progression of nuclear cataract was defined as an increase by 1.0 or more in the nuclear cataract grade. Discrete logistic regression models were used to assess associations of the 10-year incidence and progression of cataract with baseline fasting blood glucose levels. If any associations were found, change point models were used to assess whether a threshold was present.
Results: :
After adjusting for age, gender, smoking, steroid use and myopia, an overall significant association was found between the 10-year incidence of cortical cataract and baseline fasting blood glucose levels (p=0.03). We found that this association had a threshold at baseline blood glucose levels of approximately 6.0-6.3 mmol/L. Participants with fasting blood glucose levels 6.0 mmol/L or higher at baseline had an 80% greater risk of incident cortical cataract (risk ratio [RR] 1.79, 95% confidence intervals [CI] 1.25-2.57), compared to participants with glucose levels <6.0 mmol/L. A linear association was found between baseline fasting blood glucose levels and the 10-year progression of cortical cataract (RR 1.14, CI 1.01-1.29 per 1 mmol/L increase in fasting glucose). No significant associations were found, however, between baseline fasting glucose levels and the 10-year incidence or progression of nuclear or PSC cataract.
Conclusions: :
In this older population-based cohort, fasting blood glucose levels were predictors of the long-term incidence and progression of cortical cataract. An apparent threshold effect of fasting blood glucose on the incidence of cortical cataract was observed at a glucose level of 6.0 mmol/L, consistent with the clinical cut off for the diagnosis of impaired fasting glucose.
Keywords: cataract • diabetes