Our study supports some of the findings in studies in other populations and settings (the ARIC study, the Cardiovascular Health Study [CHS] and the Blue Mountains Eye Study [BMES] in Australia), in which similar approaches were used to measure retinal vessel diameters. Although all three studies used a computer-assisted imaging approach and the Parr-Hubbard formula to quantify retinal vessel diameters from digitized photographs, these studies are not directly comparable, as the sampling methodologies and sociodemographic characteristics of the study populations are different. In the ARIC study and the CHS, we used the AVR as a measure of retinal arteriolar narrowing.
10 11 12 13 14 30 31 32 This was based on the assumption that potential magnification differences between photographs could result in measurement error (e.g., vessel caliber may be artificially magnified in photographs of myopic eyes), and that the AVR would minimize such an error, because retinas with artificially magnified arterioles could be expected to have similarly magnified venules. In the middle-aged ARIC study population (
n = 8524, age 49–73 years), we reported a smaller AVR in older persons, suggesting that retinal arterioles narrow with increasing age.
30 In the older CHS population (
n = 2050, age 69–97 years), however, we found no relationship between AVR and age.
31 Our present study now suggests that both retinal arteriolar and venular diameters decrease with age. Because the age-related decline was similar in magnitude for arterioles and venules, the AVR remained relatively stable over the entire age range in the study population. The BMES in Australia (
n = 3654, age 49–98 years) also reported a similar age-related narrowing of both arterioles and venules.
33 However, the magnitude of the age-related narrowing was nearly twice that found in our population. Retinal arteriolar diameters decreased by 4.8 μm and venular diameters by a 4.1-μm per decade increase with age (after similar adjustment for gender and mean arterial BP). One possible explanation for this difference is that the sample population in the BMES was older, and it is possible that vessel narrowing was greatest in the oldest people, thus skewing the average decline for the total sample.