Temporal trends in the age-specific prevalence of diabetes and diabetic retinopathy in older persons: Population-based survey findings

Purpose: To compare the age-specific prevalence of diabetes and diabetic retinopathy (DR) over 6 years. Methods: The Blue Mountains Eye Study (BMES) examined 3654 residents (82.4% response) aged >49 years in BMES I (1992-1994). Survivors (n = 2335) and newly eligible residents (n = 1174) were examined in BMES II (1997-2000). Diabetes was defined by history or fasting plasma glucose ≥7.0 mmol/L. DR was graded from 6-field retinal photographs using the Airlie House Classification. Age-specific prevalence in 5-year intervals was compared, as samples of each age group were independent. Results: The overall diabetes prevalence increased from 7.8 to 9.9% (p = 0.002) while the age-specific prevalence increased in age groups 60-74 years, over 6 years. A slightly higher prevalence of mild levels of DR (p = 0.018) but lower prevalence of moderate-severe levels of DR (p = 0.049) was evident in BMES II compared to BMES I. Factors significantly associated with DR prevalence were diabetes duration ≥20 years (BMES I, OR 7.6 [2.9-20.5]; BMES II, OR 6.1 [2.5-15.4]) and blood glucose level (BMES I, OR 1.1 [1.0-1.2]; BMES II, OR 1.2 [1.1-1.3] per mmol/L increase). Conclusions: An increased prevalence of diabetes, but decreased prevalence of severe levels of DR, was documented in two survey samples from the same region over 6 years.