Suchergebnisse

AbstractProbability samples are the preferred method for providing inferences that are generalizable to a larger population. However, in many cases, this approach is unlikely to yield a sample size large enough to produce precise inferences. Our goal here is to improve the efficiency of inferences from a probability sample by combining (or blending) it with a nonprobability sample, which is (by itself) potentially fraught with selection biases that would compromise the generalizability of results. We develop novel methods of statistical weighting that may be used for this purpose. Specifically, we make a distinction between weights that can be used to make the two samples representative of the population individually (disjoint blending) and those that make only the combined sample representative (simultaneous blending). Our focus is on weights constructed using propensity scores, but consideration is also given to calibration weighting. We include simulation studies that, among other illustrations, show the gain in precision provided by the convenience sample is lower in circumstances where the outcome is strongly related to the auxiliary variables used to align the samples. Motivating the exposition is a survey of military caregivers; our interest is focused on unpaid caregivers of wounded, ill, or injured US servicemembers and veterans who served following September 11, 2001. Our work serves not only to illustrate the proper execution of blending but also to caution the reader with respect to its dangers, as invoking a nonprobability sample may not yield substantial improvements in precision when assumptions are valid and may induce biases in the event that they are not.

Within-survey multiple imputation (MI) methods are adapted to pooled-survey regression estimation where one survey has more regressors, but typically fewer observations, than the other. This adaptation is achieved through (1) larger numbers of imputations to compensate for the higher fraction of missing values, (2) model-fit statistics to check the assumption that the two surveys sample from a common universe, and (3) specifying the analysis model completely from variables present in the survey with the larger set of regressors, thereby excluding variables never jointly observed. In contrast to the typical within-survey MI context, cross-survey missingness is monotonic and easily satisfies the missing at random assumption needed for unbiased MI. Large efficiency gains and substantial reduction in omitted variable bias are demonstrated in an application to sociodemographic differences in the risk of child obesity estimated from two nationally representative cohort surveys.

This article distills a longer report, Hidden Heroes: America's Military Caregivers. It describes the magnitude of military caregiving in the United States, identifies gaps in support services, and offers recommendations.

Abstract

Background
The combination of exposure to multiple stressors and psychological distress may contribute to the disproportionate burden of dementia risk among Black Americans. This study estimates the effect of an index of stress and psychological distress (ie, "stress burden") on cognitive function and clinically adjudicated cognitive outcomes among older Black American adults, and examines sleep as a mediator.


Methods
The sample included 204 Black adults (79% female; mean age = 64 years) from Pittsburgh, PA, USA. Stress burden comprised 3 self-reported stress and distress measures assessed in 2016: discrimination, psychological distress, and posttraumatic stress. Potential mediators included actigraphy-assessed sleep duration and efficiency from 2018. Cognitive battery and clinical adjudication in 2019 assessed cognitive function and clinically adjudicated outcomes. Causal mediation analysis estimated the direct effect between stress burden and cognitive outcomes, and indirect effects through sleep, after adjusting for sociodemographics and hypertension.


Results
Higher stress burden had a significant direct effect on lower executive functioning and visuospatial performance. However, there were no significant indirect effects (ie, mediation) by sleep disturbances on any domain of cognitive function assessed. Also, there were no significant direct or indirect effects on clinically adjudicated outcomes.


Conclusions
Multiple stressors often co-occur and may contribute to racial disparities in cognitive health. Findings suggest that higher stress burden had negative effects on functioning in executive and visuospatial domains in this community-based sample of older Black American adults. However, there was no evidence of mediation by sleep. Findings highlight the importance of continued work to identify modifiable pathways between stress burden and cognitive health disparities.