Microvascular network alterations in the retina of patients with Alzheimer's disease.

BACKGROUND: Although cerebral small-vessel disease has been implicated in the development of Alzheimer's disease (AD), the cerebral microcirculation is difficult to visualize directly in vivo. Because the retina provides a noninvasive window to assess the microcirculation, we determined whether quantitatively measured retinal microvascular parameters are associated with AD. METHODS: We conducted a case-control study (case:control matching ≈ 1:2). Retinal photographs were analyzed using a computer program, and a spectrum of quantitative retinal microvascular parameters (caliber, fractal dimension, tortuosity, and bifurcation) were measured. Logistic regression models were used to compute the odds ratio (OR) and 95% confidence interval for AD adjusting for age, gender, ethnicity, smoking, hypertension, diabetes, hypercholesterolemia, and history of myocardial infarction. RESULTS: We included 136 demented patients with AD and 290 age-gender-race-matched controls. Persons with narrower venular caliber (OR per standard deviation [SD] decrease, 2.01 [1.27-3.19]), decreased arteriolar and venular fractal dimension (OR per SD decrease 1.35 [1.08-1.68], 1.47 [1.17-1.84], respectively) and increased arteriolar and venular tortuosity (OR per SD increase, 1.84 [1.40-2.31], 1.94 [1.48-2.53], respectively) were more likely to have AD. These associations still persisted when only AD cases without a history of cerebrovascular disease were included. CONCLUSIONS: Patients with AD have altered microvascular network in the retina (narrower retinal venules and a sparser and more tortuous retinal vessels) compared with matched nondemented controls. These changes in retinal microvasculature may reflect similar pathophysiological processes in cerebral microvasculature in the brains of patients with AD.

Epidemiology of dementia in Asia: insights on prevalence, trends and novel risk factors.

Asia is the most populous region in the world and its rapidly growing societies are the sources of global development. However, accompanying this rapid growth is aging of the population with increasing occurrence of diseases, of which dementia is the most prominent, which provide major challenges to healthcare systems. Dementia prevalence in Asia has previously been found to be lower than Western populations, but recent studies show that age-specific prevalence rates are similar globally. Overall dementia prevalence is expected to rise dramatically across Asia due to maturing populations. Earlier Asian studies reported a lower prevalence of Alzheimer's disease (AD) and a higher prevalence of vascular dementia (VaD). Recent studies, however, show a reversal of this ratio that now parallels that of Western countries. This change may be attributed to an altered demographic profile, urbanization, environmental reactions, ethnicity and advances in the use of neuroimaging modalities. Several factors may influence the results of epidemiological studies including changes in societal perception of aging, family attitudes, validity of assessment tools due to language and literacy, and medical practitioners' expertise in recognizing dementia. Nevertheless, epidemiological studies in Asia may reveal factors contributory to inter-ethnic differences in dementia. Potentially modifiable risk factors apparent only in low and middle-income countries and gene-environment interactions may underlie these disparities and identification of such factors may lead to effective treatments.