The association between retinal vascular fractal dimension and cognitive function in the community‐dwelling elderly cohort TIGER

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AbstractBackgroundCerebral vascular factor plays an important role in the pathogenesis of cognitive dysfunction, including mild cognitive impairment (MCI) and dementia. The small retinal vessels reflect cerebral microcirculation and its fractal dimension (Df) representing the complexity of the retinal microcirculation. However, the connection between the retinal circulation and cognitive function lacked consistent and longitudinal evidence. This study aimed to explore the association between the retinal vascular Df and cognitive dysfunction in the community‐dwelling older adults.MethodThis study is part of a prospective cohort Taiwan Initiative for Geriatric Epidemiological Research (TIGER, 2011 to present). Participants from the 4‐year (2015–2017) and 6‐year (2017‐2019) follow‐ups were included. Global and domain‐specific cognitive function were assessed at the 4‐year and 6‐year follow‐ups. Fundus photography was taken for each participant at the 4‐year follow‐up, and retinal vessels were segmented for fractal analyses. Multivariable logistic regression analyses were performed to explore the association between Df of the retinal vessels and cognitive decline over 2 years adjusting for age, gender, years of education, diabetes, hypertension, hyperlipidemia, cardiovascular event, smoking, drinking and age‐related macular degeneration.ResultHigher right retinal vascular complexity (right Df) was associated with the decline of logical memory‐recall I [linear right Df: adjusted odds ratio (aOR)= 0.30, 95% confidence interval (CI)= 0.11 to 0.85). No significant linear association was found between Df and global cognition or other cognitive domains. For non‐linear relationship, we found an inverted U shape association between the right Df and global cognitive decline over 2 years [quadratic right Df: aOR=0.10, 95% CI = 0.01‐0.80]. The risk of global cognitive decline (assessed by MoCA‐T) was 0.1 when right Df change 0.1 unit (increase or decrease) from the sample mean (1.36). Similar nonlinear relationship was found for the decline of logical memory‐recall II over 2 years (quadratic right Df: aOR= 0.08, 95% CI= 0.01‐0.59). No significant association was found between left Df and cognitive decline over 2 years.ConclusionThis study demonstrated a nonlinear relationship between the retinal vascular complexity of the right eye and the decline of global cognition and logical memory. This retinal biomarker may be used for screening dementia in the preclinical stage.