An Italian research team based in Milan has reported that functional and morphological changes in the retinal vasculature can be identified within Alzheimer’s disease (AD) or mild cognitive impairment (MCI) participants. The study, published in Scientific Reports ((2019) DOI:10.1038/s41598-018-37271-6), stated that “we demonstrated that vascular changes characterize these disorders and that such alterations are mainly limited to the arterial function, rather than a vascular loss. Future studies with extended longitudinal follow up of the studied cohort may provide additional substantive information and retinal vascular parameters may prove to be a useful biomarker for monitoring the efficacy of AD and MCI, or to predict the disease progression”.
The research team believes that Alzheimer’s disease has an estimated prevalence of 36.5 million and that the disease is preceded by a variable transitional phase termed “mild cognitive impairment” (MCI). Small vessel disease of the brain has been “demonstrated to be implicated in AD and MCI pathogenesis”, furthermore, “these neurodegenerative disorders are associated with early neurovascular dysfunction, which leads to an altered blood flow regulation and contributes to disease pathogenesis”. This study on the small vessels of the brain has led researchers to apply the same techniques in the topographic qualitative investigation and quantitative measurements of vessels of the retina: both studies use dynamic vessel analyzer (DVA) and optical coherence tomography angiography (OCTA) devices.
The report analyzed research among twelve (12) subjects with AD, twelve (12) subjects with MCI, and thirty-two (32) gender- and age-matched controls were prospectively enrolled. Mean ± SD age was 72.9 ± 7.2 years in the AD group, 76.3 ± 6.9 years in the MCI group, and 71.6 ± 5.9 years in the control group (p = 0.104). In the DVA dynamic analysis, the arterial dilation was decreased in the AD group (0.77 ± 2.06%), in the comparison with the control group (3.53 ± 1.25%, p = 0.002). The reaction amplitude was decreased both in AD (0.21 ± 1.80%, <0.0001) and MCI (2.29 ± 1.81%, p = 0.048) subjects, compared with controls (3.86 ± 1.94%). OCTA variables did not differ among groups. The research group stated that in the Pearson correlation analysis, amyloid β level in the cerebrospinal fluid was directly correlated with the arterial dilation (R = 0.441, p = 0.040) and reaction amplitude (R = 0.580, p = 0.005). According to the results, this study demonstrate that Alzheimer’s and MCI subjects are characterized by a significant impairment of the retinal neurovascular coupling. This impairment is inversely correlated with the level of amyloid β in the cerebrospinal fluid.