Cystatin C, cognition, and brain MRI findings in 90+-year-olds.

Chronic kidney disease is emerging as a novel risk factor for cerebrovascular disease, but this association remains largely unexplored in older adults. Cystatin C is a more accurate measure than creatinine of kidney function in the elderly. We evaluated cystatin C, cognitive function, and brain imaging in 193 participants from The 90+ Study neuroimaging component. The mean age was 93.9 years; 61% were women. Mean cystatin C was 1.62 mg/L with estimated glomerular filtration rate 39.2 mL/min/1.73 m. Performance on measures of global cognition, executive function, and visual-spatial ability declined at higher tertiles of cystatin C (lower kidney function). Higher cystatin C was significantly associated with infratentorial microbleeds and lower gray matter volume. Adjusted risk of incident dementia was increased in the middle and high cystatin C tertile groups compared with the low group (hazard ratio in highest tertile 3.81 [95% confidence interval 1.14-12.7]), which appeared to be explained in part by the presence of cerebral microbleeds. Overall, cystatin C was associated with cognitive performance, brain imaging pathology, and decline to dementia in this oldest-old cohort.