Diabetes mellitus and incident glaucoma in Australia: a 10-year cohort study from the 45 and Up Study.

Background: Understanding the relationship between diabetes mellitus (DM) and the severity of glaucoma is important for the primary prevention of incident glaucoma. This paper aims to examine the association between DM and incident glaucoma. Methods: The 45 and Up Study is a prospective cohort study where Australians aged ≥45 years old were enrolled. The incident of glaucoma at follow-up is the main outcome measured. Glaucoma incidence was identified as those with recorded glaucoma-related medication from the Pharmaceutical Benefits Scheme or surgery recorded in the Medicare Benefits Schedule. Patients with glaucoma were classified into the medical glaucoma group (with glaucoma-related medication but not surgery) and the surgical glaucoma group (with glaucoma-related surgery). A Cox regression model was used to calculate the hazard ratios (HRs) to examine the association between baseline DM and the risk of developing glaucoma during the follow-up period. The reference groups are as follows: (I) non-DM participant; (II) participant with DM, duration between 0 and 5 years; (III) participant uses insulin. Results: A total of 255,547 eligible participants, with no glaucoma diagnosis at baseline, were included. During the follow-up period, 7,667 patients (3.0%) were identified as medical glaucoma only and 2,326 patients (0.9%) underwent glaucoma surgery. After controlling for confounders, baseline DM was associated with an increased risk of glaucoma in the medical glaucoma group only [hazard ratio (HR) =1.36, 95% confidence interval (CI) =1.07-1.72, P=0.002]. However, baseline DM (HR =0.97, 95% CI =0.57-1.65, P=0.979) was not associated with an increased risk of surgical glaucoma. Conclusions: DM was associated with an increased risk of medical glaucoma only, there was no association identified with surgical glaucoma in the Australian population recruited in the 45 and Up Study.