Determinants and Risk Factors for Central Corneal Thickness in Japanese Persons: The Funagata Study

Purpose: To examine the association between glucose metabolism and central corneal thickness (CCT) in Japanese adults. Methods: A sub-sample of 322 Japanese adults participating in the Funagata Study was included in this analysis. CCT was measured using a specular microscope. Glucose metabolism was examined using 75-g oral glucose tolerance test. Mean differences in CCT (mu m) and 95% confidence intervals were estimated with univariate, age-sex-adjusted and multivariate models using multiple linear regression. Results: The mean (+/- standard deviation) age of the study sample was 63.7 +/- 11.4 years and 44% were men. The mean fasting plasma glucose (FPG), 2-hour post-load plasma glucose (2hPG) and haemoglobin A1c (HbA1c) concentrations were 96.8 +/- 12.6mg/dl, 123.6 +/- 41.2mg/dl and 5.3 +/- 0.4%, respectively. CCT was normally distributed in the study sample, and the mean CCT was 544.7 +/- 34.6 mu m. After multivariate adjustment, characteristics associated with increased CCT were 2hPG and HbA1c concentrations, impaired glucose tolerance, diabetes, body weight or body mass index and current smoking. Conclusion: Impaired glucose tolerance, diabetes, obesity and current smoking are associated with increased CCT. Additional studies are required to examine whether interventions to affect these characteristics may reduce CCT.