Standardized Screening for cognitive impairment

Cognitive function was assessed with the Montreal Cognitive Assessment (MoCA) (supplementary data 1) [23]. The MoCA is a validated, clinic-based tool that samples from various domains of cognition and is sensitive in detecting mild cognitive impairment. MoCA consists of a single page test with a maximum score of 30 (range: 0–30). The MoCA takes less than 10 minutes to complete and assesses seven domains of cognition: visuospatial/executive, naming, memory (delayed recall), attention, language, abstraction and orientation. The original English version 7.1 was used (http://www.mocatest.org/paper-tests/moca-test-full/). We chose MoCA over the more commonly used mini-mental state exam (MMSE) for detecting cognitive impairment, as the latter is more focused on memory rather than domains such as executive function, that are more commonly affected in kidney disease [25]. Compared to MMSE, MoCA has a better ability to detect vascular dementia with a higher area under the curve [26].

The MoCA was administered by medical assistants who underwent an hour of training that included detailed review of the online instructions on MoCA along with practice sessions on mock patients. MoCA was administered in a private room to minimize distraction and assure confidentiality.