Neighborhood-level Social Determinants of Health and Waitlist Mortality for Liver Transplantation: The Liver Outcomes and Equity Index.

BACKGROUND AND AIMS: To examine neighborhood-level disparities in waitlist mortality for adult liver transplantation (LT), we developed novel area-based social determinants of health (SDOH) index using a national transplant database. METHODS: ZIP Codes of individuals listed for or received LT in the Scientific Registry of Transplant Recipients database between June 18, 2013, and May 18, 2019, were linked to 36 American Community Survey (ACS) variables across 5 SDOH domains for index development. A step-wise principal component analysis was used to construct the Liver Outcomes and Equity (LOEq) index. We then examined the association between LOEq quintiles (Q1 = worst and Q5 = best neighborhood SDOH) and waitlist mortality with competing risk regression among listed adults in the study period and acuity circle (AC) era. RESULTS: The final LOEq index consisted of 13 ACS variables. Of 59 298 adults waitlisted for LT, 30% resided in LOEq Q5 compared with only 14% in Q1. Q1 neighborhoods with worse SDOH were disproportionately concentrated in transplant regions with low median Model for End-Stage Liver Disease at transplant (MMAT) and shorter wait times. Five years cumulative incidence of waitlist mortality was 33% in Q1 in high MMAT regions versus 16% in Q5 in low MMAT regions. Despite this allocation advantage, LOEq Q1-Q4 were independently associated with elevated risk of waitlist mortality compared with Q5, with highest increased hazard of waitlist deaths of 19% (95% CI, 11%-26%) in Q1. This disparity persisted in the AC era, with 24% (95% CI, 10%-40%) increased hazard of waitlist deaths for Q1 versus Q5. CONCLUSIONS: Neighborhood SDOH independently predicts waitlist mortality in adult LT.

An Actuated Neural Probe Architecture for Reducing Gliosis-Induced Recording Degradation.

Glial encapsulation of chronically implanted neural probes inhibits recording and stimulation, and this signal loss is a significant factor limiting the clinical viability of most neural implant topologies for decades-long implantation. We demonstrate a mechanical proof of concept for silicon shank-style neural probes intended to minimize gliosis near the recording sites. Compliant whiskers on the edges of the probe fold inward to minimize tissue damage during insertion. Once implanted to the target depth and retracted slightly, these whiskers splay outward. The splayed tips, on which recording sites could be patterned, extend beyond the typical 50-100 [Formula: see text] radius of a glial scar. The whiskers are micrometer-scale to minimize or avoid glial scarring. Electrically inactive devices with whiskers of varying widths and curvature were designed and monolithically fabricated from a 5- [Formula: see text] silicon-on-insulator (SOI) wafer, and their mechanical functionality was demonstrated in a 0.6% agar brain phantom. Deflection was plotted versus deflection speed, and those that were most compliant actuated successfully. This probe requires no preparation for use beyond what is typical for a shank-style silicon probe.