Research Spotlights August 2020

Research Spotlights August 2020

States that were slower to implement social distancing orders saw higher COVID-19 death rates

As seen in the current Covid-19 pandemic, social distancing is encouraged to mitigate viral spreading during outbreaks, however, the association between distancing and patient-centered outcomes has not been previously demonstrated. Research supported by the NHLBI capitalizes on the variation in state response to the Covid-19 pandemic (as defined by emergency declarations and school closures) to examine the relationship with the states’ response and Covid-19 mortality.

The researchers estimate negative binomial regressions to test the association between timing of state emergency declarations and, separately, school closures, with mortality using 55,146 Covid-19 deaths. Day 1 for each state was set to when the state recorded 10 or more Covid-19 deaths. Descriptively, 37 of 50 states had ≥ 10 deaths and 28 follow-up days. According to the regression analyses, both later emergency declaration and later school closure were associated with more deaths (later emergency declaration: adjusted mortality rate ratio [aMRR] 1.05 per day delay, 95% CI 1.00 to 1.09, p=0.040; school closure (aMRR 1.05, 95% CI 1.01 to 1.09, p=0.008). When assessing all 50 states and setting day 1 to the day a state recorded its first death, delays in declaring an emergency (aMRR 1.05, 95% CI 1.01 to 1.09, p=0.020) or closing schools (aMRR 1.06, 95% CI 1.03 to 1.09, p<0.001) were associated with more deaths. Testing for sensitivity, results were consistent even when excluding New York and New Jersey.

The findings from this study showed that each day of delayed intervention lead to a 5-to-6% increase in Covid-19 mortality risk. These results from were similar even when the data from New York and New Jersey were excluded to account for the impact of excess deaths from the New York City area. The authors did note some of the limitations of their research, which include the inability to adjust for potentially important confounders, such as outbreaks in long-term care facilities, individual behavior (measures were only at a state level), and state-level variation in access to healthcare. Despite these limitations, this study provides real-time, scientific evidence of the efficacy of social distancing measures and may help inform future policy decisions. In summary, this paper demonstrates that later state-wide emergency declarations and school closure were associated with higher Covid-19 mortality.

Citation:
Yehya N, Venkataramani A, Harhay MO. 2020. Statewide Interventions and Covid-19 Mortality in the United States: An Observational Study, Clinical Infectious Diseases. ciaa923, https://doi.org/10.1093/cid/ciaa923

Senses can indicate dementia risk in older adults

In a recent publication, researchers funded by NIA, NIH Blueprint for Neuroscience Research, NSF, and others, researchers developed a summary score for impairments in multiple senses (vision, hearing, taste, touch, smell) and evaluated its association with dementia in older adults. Previous research has indicated that sensory impairments are associated with dementia risk, but few studies have looked at the additive effects of multiple impairments in sensory function.

The investigators studied a diverse group of older adults in the Health, Aging and Body Composition (Health ABC) Study, which is a prospective cohort study of well-functioning 3075 black and white women and men aged 70-79 years of age. In this study, the researchers focused their analysis on 1794 participants for up to 10 years to determine if multisensory functioning correlated with the development of dementia. Cognitive testing was done at the beginning of the study and repeated every other year. Dementia was defined by testing that showed a significant drop from baseline scores, documented use of a dementia medication or hospitalization for dementia as a primary or secondary diagnosis. Multisensory testing was done in the third-to-fifth year and included hearing (hearing aids were not allowed), contrast-sensitivity tests for vision (glasses were permitted), touch testing in which vibrations were measured in the big toe, and smell, involving identifying distinctive odors like paint-thinner, roses, lemons, onions and turpentine. The multisensory function score (0 to 12 points) was based on sample quartiles of objectively measured vision, hearing, smell, and touch summed overall. Risk of incident dementia and cognitive decline associated with the score were assessed in regression models adjusting for demographics and health conditions.

At the time of enrollment, all participants were dementia-free, however 328 participants (18%) developed dementia over the course of the study. The researchers found that the risk of cognitive decline and dementia increased in a dose-response manner as multisensory functioning decreased. Participants whose sensory levels ranked in the poor range (104, 27%) were more likely to develop dementia compared with those participants in the middle range (141, 19%) and in the good range (83, 12%). Participants who remained dementia-free generally had better cognitive function at enrollment and tended to have no sensory impairments. The participants with good multisensory function (780) were more likely to be healthier than participants with poor multisensory function (499), which may indicate that some lifestyle habits play a role in reducing risks for dementia. The participants with good multisensory functioning were more likely to have completed high school (85% versus 72.1%), have fewer diabetes diagnoses (16.9% versus 27.9%) and a slightly lower prevalence of cardiovascular disease, high-blood pressure and stroke.

These results indicate a link between deteriorating multisensory functioning and an increased the risk of dementia. Moreover, even mild or moderate multisensory impairments were associated with an increased risk of dementia, which may indicate that people with poor multisensory function could be a high-risk population that could be targeted for an intervention prior to dementia onset. More research is needed to determine the exact mechanisms underlying this association. It is possible that sensory impairments could be due to underlying neurodegeneration or disease processes that also affect cognition. However, it is also possible that sensory impairments, could accelerate or promote cognitive decline, either directly impacting cognition or indirectly by increasing social isolation, poor mobility and adverse mental health. While multiple impairments were the focus of the researchers work, the investigators noted that the sense of smell, or olfaction, has a stronger association with dementia than the other senses of touch, hearing, or vision. Participants whose smell declined by 10% had a 19% higher chance of dementia, versus a 1-3% increased risk for corresponding declines in vision, hearing, and touch. This may be due to the olfactory bulb, which is critical for smell, being affected early in dementia-related disease, potentially making olfaction a preclinical indicator of dementia.

Citation:
Brenowitz WD, Kaup AR, Yaffe K. 2020. Incident dementia and faster rates of cognitive decline are associated with worse multisensory function summary scores. Alzheimers Dement. doi: 10.1002/alz.12134

Racial discrimination may negatively impact cognition in African American women

A study supported by the NCI, NIA, and the Alzheimer's Association, tested the hypothesis that frequency of racist experiences among African American women negatively impacts subjective cognition function (SCF). Previous studies have shown that African Americans have higher rates of incident dementia and Alzheimer's disease than Caucasian Americans. Additionally, older African Americans perform more poorly on neuropsychological tests of cognition compared to aged-matched Caucasian Americans of similar ages in many studies of community and clinical populations. While controlling for education and socioeconomic status, both independently associated with cognitive function, may attenuate observed racial disparities, it does not usually eliminate them. Racial discrimination has previously been associated with many adverse health outcomes and may contribute to these disparities. In this study, the investigators sought to test if this psychological stress due to racism is also associated with memory decline.

To answer their research question, the researchers estimated multinomial logistic regressions to quantify the association between experiences of racism and SCF; the model was estimated based on six questions asked of 17,320 participants (ages 21-69) in the Black Women's Health Study. Each positive response was assigned 1 point for a total cognitive score ranging from 0 to 6 and categorized as good cognitive function (0 positive responses), moderate cognitive function (1 to 2 positive responses), and poor cognitive function (3 to 6 positive). Using multi-regression models, they found that experiences of both daily and institutional racism were associated with decreased SCF. Women reporting the highest level of daily racism had 2.75 times the risk of poor SCF as women reporting the lowest level of daily racism. Analyses also indicated that depression and insomnia mediated these relationships.

This study provides evidence of an association of experiences of racism with poorer SCF, suggesting that the chronic stress associated with racial discrimination may contribute to racial disparities in cognition and Alzheimer’s Disease. Further research is needed to determine whether exposure to institutional and daily racism also increases Alzheimer’s related biomarkers (e.g., PET imaging of amyloid and tau) and the conversion to Alzheimer's dementia in this population. One limitation of this study is that the data was collected retrospectively, so that this deficit in cognition could have preceded, and therefore impacted, perceptions of racism. Additional prospective studies that use objective measures of cognition before and after perceived experiences of racism will be important to confirm these results. That said, this research provides evidence that a highly prevalent psychosocial stressor among African Americans, racism, is associated with lower perceived cognitive function.

Citation:
Coogan P, Schon K,  Li S, Cozier Y, Bethea T,  Rosenberg L. 2020. Association of Experiences of racism and subjective cognitive function in African American women. Alzheimers Dement. 2020;12:e12067.

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