Abstract
Purpose:
Cerebral small-vessel disease has been implicated in the development of Alzheimer’s disease (AD). The retinal microvasculature is accessible through non-invasive visualisation and parameters measured can be used to assess the systemic microcirculation. We evaluated retinal microvascular parameters in a prospective case-control study of AD patients and cognitively normal controls.
Methods:
Cases had a diagnosis of AD established by a senior clinician using NINCDS ADRDA criteria during routine care at a hospital memory clinic. Controls were individuals >65 years of age with a mini-mental state examination (MMSE) score >26 out of 30. Retinal photographs were analyzed using a computer-assisted program (Singapore I Vessel Assessment, SIVA), and quantitative retinal microvascular parameters measured (caliber, fractal dimension, tortuosity, and bifurcation). Logistic regression models were used to compute the odds ratio (OR) and 95% confidence interval for AD adjusting for age, gender, smoking, hypertension, diabetes, and history of cardiovascular and cerebrovascular disease. This research was approved by the Office of Research Ethics Committee Northern Ireland.
Results:
Data from 191 AD cases and 298 cognitively normal controls were analysed. Participants with decreased venular fractal dimension were more likely to have AD (P=0.015) following adjustment for age, gender, smoking, hypertension, diabetes, and history of cardiovascular and cerebrovascular disease (OR per standard deviation decrease of 1.30 [95% confidence interval, 1.05-1.60]). Other measured retinal vascular parameters were not associated with AD.
Conclusions:
Patients with AD have an altered microvascular network in the retina (sparser retinal venules) compared with cognitively normal controls. The changes observed in retinal microvasculature may reflect similar pathophysiological processes in the cerebral microvasculature in the brains of patients with AD.