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INTRODUCTION: Limited observational windows lead to conflicting results in studies examining educational differences in Alzheimer's disease and related dementias (ADRD) risk, due to observational window bias relative to onset of accelerated cognitive decline. This study tested a novel model to address observational window bias and tested for the presence and sources of disparities in accelerated cognitive declines due to ADRD. METHODS: The sample examined 167,314 cognitive assessments from 32,441 Health and Retirement Study participants. We implemented a parametric non-linear nested longitudinal regression and reported multivariable-adjusted nodal incidence ratios (aNIR). RESULTS: University degrees were associated with lower incidence (aNIR = 0.253, 95% confidence interval [CI] = [0.221 to 0.289], p < 0.001), while black participants had a higher incidence (aNIR = 1.995, [1.858 to 2.141], p < 0.001) of accelerated cognitive decline, adjusting for demographic, sociobehavioral, and medical risk factors. Sex-stratified analyses identified diminished educational returns for women and increased incidence among minoritized women. DISCUSSION: Addressing observational window bias reveals large social inequalities in the onset of accelerated cognitive declines indicative of ADRD. HIGHLIGHTS: This study identifies observational window bias as a source of conflicting results among previous studies of educational achievement in Alzheimer's disease and related dementias (ADRD) disparities. The study locates preclinical accelerated cognitive decline, which is indicative of ADRD while occurring 10+ years prior to symptom onset, as a site to study ADRD disparities that mitigates observational window bias. A novel method, nested non-linear regression, is developed to test for differences in the onset of accelerated cognitive decline. Educational and racial/ethnic disparities are demonstrated in the onset of accelerated cognitive decline, as are their intersecting differences with sex/gender.
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BACKGROUND: In December 2020 the U.S. began a massive COVID-19 vaccination campaign, an action that researchers felt could catalyze inequalities in COVID-19 vaccination utilization. While vaccines have the potential to be accessible regardless of social status, the objective of this study was to examine how and when socioeconomic status (SES) and racial/ethnic inequalities would emerge in vaccination distribution. METHODS: Population vaccination rates reported at the county level by the Centers for Disease Control and Prevention across 46 states on 3/30/2021. Correlates included SES, the share of the population who were Black, Hispanic, Female, or aged ≥65 years, and urbanicity (thousands of residents per square mile). Multivariable-adjusted analyses relied on zero-inflated negative binomial regression to estimate the odds of providing any vaccine, and vaccination rate ratios (aVRR) comparing the distribution rate for vaccinations across the U.S. RESULTS: Across the U.S., 16.3 % of adults and 37.9 % of adults aged 65 and older were vaccinated in lower SES counties, while 20.45 % of all adults and 48.15 % of adults aged 65 and older were vaccinated in higher SES counties. Inequalities emerged after 41 days, when < 2 % of Americans were vaccinated. Multivariable-adjusted analyses revealed that higher SES was associated with improved vaccination distribution (aVRR = 1.127, [1.100-1.155], p < 1E-06), while increases in the percent reporting Black or Hispanic race/ethnicity was associated with lower vaccination distribution (aVRR = 0.998, [0.996-0.999], p = 1.03E-04). CONCLUSIONS: Social inequalities in COVID-19 vaccines reflect an inefficient and inequitable distribution of these technologies. Future efforts to improve health should recognize the central role of social factors in impacting vaccine delivery.