Association of Neighborhood-Level Socioeconomic Factors With Delay to Hospital Arrival in Patients With Acute Stroke.

BACKGROUND AND OBJECTIVES: Delivery of acute ischemic stroke (AIS) therapies is contingent on the duration from last known well (LKW) to emergency department arrival time (EDAT). One reason for treatment ineligibility is delay in presentation to the hospital. We evaluate patient and neighborhood characteristics associated with time from LKW to EDAT. METHODS: This was a retrospective observational study of patients presenting to the Yale New Haven Hospital in the AIS code pathway from 2010 to 2020. Patients presenting within 4.5 hours from LKW who were recorded in the institutional Get With the Guidelines Stroke registry were classified as early while those presenting beyond 4.5 hours were designated as late. Temporal trends in late presentation were explored by univariate logistic regression. Using variables significant in univariate analysis at p < 0.05, we developed a mixed-effect logistic regression model to estimate the probability of late presentation as a function of patient-level and neighborhood (ZIP)-level characteristics (area deprivation index [ADI] derived from the Health Resources and Services Administration), adjusted for calendar year and geographic distance from the centroid of the ZIP code to the hospital. RESULTS: A total of 2,643 patients with AIS from 2010 to 2020 were included (63.4% presented late and 36.6% presented early). The frequency of late presentation increased significantly from 68% in 2010 to 71% in 2020 (p = 0.002) and only among non-White patients. Patients presenting late were more likely to be non-White (37.1% vs 26.9%, p < 0.0001), arrive by means other than emergency medical services (EMS) (32.7% vs 16.1%, p < 0.0001), have an NIHSS <6 (68.7% vs 55.2%, p < 0.0001), and present from a neighborhood with a higher ADI category (p = 0.0001) that was nearer to the hospital (median 5.8 vs 7.7 miles, p = 0.0032). In the mixed model, the ADI by units of 10 (odds ratio [OR] 1.022, 95% confidence interval [CI] 1.020-1.024), non-White race (OR 1.083, 95% CI 1.039-1.127), arrival by means other than EMS (OR 1.193, 95% CI 1.145-1.124), and an NIHSS <6 (OR 1.085, 95% CI 1.041-1.129) were associated with late presentation. DISCUSSION: In addition to patient-level factors, socioeconomic deprivation of neighborhood of residence contributes to delays in hospital presentation for AIS. These findings may provide opportunities for targeted interventions to improve presentation times in at-risk communities.

Could Mesophases Play a Role in the Nucleation and Polymorph Selection of Zeolites?

Zeolites and mesoporous silicas are porous materials with important applications in catalysis, gas storage, and separation. Zeolite crystals form in the presence of cationic surfactants that act as structure directing agents (SDAs). The way SDAs control the nucleation and polymorphs selection in zeolites is not fully understood. The formation of mesoporous silica is templated by liquid crystalline mesophases that result from frustrated attraction between silicates and long-chain SDAs. Experiments indicate that surfactants C nH2 n+1(CH3)3N+ with n > 6 yield mesoporous silicas, and the one with n = 6 produces a zeolite. This suggests that the driving force toward mesophase formation is also present for small organocations, but is overcome by the ability of silica to wrap a crystal lattice around them. Here we use molecular dynamics simulations to investigate whether the existence of metastable mesophases can play a role in the nucleation and polymorph selection of zeolitic crystals. As a proof of concept, we investigate the phase behavior of simple mesogenic mixtures of SDAs and a network former T that favors tetracoordinated crystals. We represent the network-former T by Stillinger-Weber models of water and silicon, in lieu of silica, because a computationally efficient silica potential that would allow for the spontaneous nucleation of zeolites in molecular dynamics simulations is not yet available. The mixtures of T and SDA produce a rich phase diagram that encompasses the sII clathrate and at least six zeolites, including sigma-2 (SGT). We find that the nucleation of SGT is not assisted by a mesophase. The nucleation of the other five zeolites of this study, however, is facilitated by the existence of metastable mesophases that decrease the nucleation barriers and direct the selection of the crystal polymorph. Together with the experimental support for mesophases in mixtures of silicates and SDAs, our results for model systems suggest that metastable mesophases could play a prominent role in promoting the nucleation and polymorph selection of some zeolites.