A Guide to Global Population Projections

Interdisciplinary studies that draw on long-term, global population projections often make limited use of projection results, due at least in part to the historically opaque nature of the projection process. We present a guide to such projections aimed at researchers and educators who would benefit from putting them to greater use. Drawing on new practices and new thinking on uncertainty, methodology, and the likely future courses of fertility and life expectancy, we discuss who makes projections and how, and the key assumptions upon which they are based. We also compare methodology and recent results from prominent institutions and provide a guide to other sources of demographic information, pointers to projection results, and an entry point to key literature in the field.forecasting, population projections, projection methodology, uncertainty

Assessment of Select Climate Change Impacts on U.S. National Security

This report examines climate change impacts to U.S. national security by quantifying select impacts globally at the national level and identifying countries that are both at high risk from projected climate change and possess risk factors associated with political instability. Exposure to global sea‐level rise risk exposure is quantified by identifying low‐elevation coastal zones (LECZ), at 1, 3, 5, 7, 9, 10 and 12 meters of elevation. Countries with high risk factors for instability that also have the most people exposed to sea‐level rise include China, Philippines, India, and Indonesia. Those with the greatest percentage of population so exposed include Philippines, Egypt, and Indonesia. Within these countries, Egypt has especially high rates of population growth within the LECZ. Aggregate climate change vulnerability is quantified by using an index that takes into account both projected temperature change and adaptive capacity. For countries with high risk factors for instability, the most vulnerable countries are South Africa, Nepal, Morocco, Bangladesh, Tunisia, Paraguay, Yemen, Sudan and Côte d’Ivoire. Water scarcity is examined by comparing numbers of people living under conditions of water in the present with three future scenarios – one in which the climate remains unchanged but population changes; one in which population changes but the climate remains static; and one in which both population and climate change. Countries with high risk factors for instability that are projected to have the biggest increases in water scarcity are Mozambique, Côte d’Ivoire, Nigeria, Iraq, Guatemala, Zimbabwe, Ethiopia, Somalia, China, Syria and Algeria

Late-life memory trajectories in relation to incident dementia and regional brain atrophy

The trajectory, or slope, of cognitive decline may provide differentiation of older adults with and without incipient neurodegenerative disease. Cognitive aging phenotypes based on memory trajectories could be used as outcome measures for clinical trials or observational studies of risk and protective factors for dementia. This study used growth mixture modeling (GMM) to identify trajectory groups based on age- and education-corrected composite memory scores derived from immediate, delayed and recognition trials of the Selective Reminding Test. Participants included 2593 participants initially without dementia (mean age at entry = 76) in a community-based study of aging and dementia in northern Manhattan. Trajectory groups were compared on consensus diagnoses of dementia and structural MRI measures of hippocampal volume and entorhinal cortical thickness. Heterogeneity in memory trajectories allowed us to identify four groups: Stable-High (43.5 %), Stable-Low (17.1 %), Decliner (26.8 %), and Rapid Decliner (12.5 %). Decliners had more brain atrophy and higher rates of conversion to dementia. This study highlights the heterogeneity in cognitive aging and provides evidence that most elderly maintain memory function as they age. Associations with dementia and imaging measures validate subgroups of older adults identified with GMM based on their memory trajectories. Future research should use these memory trajectory phenotypes to determine whether dementia risk and protective factors differ for individuals following different memory trajectories

Dementia Risk and Protective Factors Differ in the Context of Memory Trajectory Groups

Background: Previous research has identified multiple risk and protective factors for late onset Alzheimer’s disease (LOAD). However, it is not known whether these risk and protective factors differ for individuals who are cognitively stable versus those already experiencing declines. Objective: This study examined how dementia risk factors differ across subgroups of older adults defined by memory trajectory. This line of research may lead to more individualized risk profiles. Methods: Risk factors for incident LOAD were compared across previously-validated groups of older adults exhibiting different memory trajectories (“Stable-High,” “Stable-Low,” “Decliner,” “Rapid Decliner”) using stratified Cox regressions. Participants included 2,593 racially/ethnically diverse older adults (mean age of 76 at study entry) in the Washington HeightsInwood Columbia Aging Project. Results: Predictors of incident dementia differed across trajectory groups: older age only incurred independent risk in stable groups, education did not incur independent protection in the rapidly declining group, depression only incurred independent risk in the stable-low group, stroke incurred independent risk in the two extreme groups, and APOE-␧4 only incurred independent risk in the rapidly declining group. Conclusion: The finding that different risk factors for LOAD were associated with specific memory trajectories may reflect the existence of resilience or vulnerability factors that modify the individual influences of risk/protective factors. This study highlights the utility of considering interactions between dementia risk factors and a patient’s unique cognitive history

Characterizing Embryonic Gene Expression Patterns in the Mouse Using Nonredundant Sequence-Based Selection

This article investigates the expression patterns of 160 genes that are expressed during early mouse development. The cDNAs were isolated from 7.5 d postcoitum (dpc) endoderm, a region that comprises visceral endoderm (VE), definitive endoderm, and the node–tissues that are required for the initial steps of axial specification and tissue patterning in the mouse. To avoid examining the same gene more than once, and to exclude potentially ubiquitously expressed housekeeping genes, cDNA sequence was derived from 1978 clones of the Endoderm library. These yielded 1440 distinct cDNAs, of which 123 proved to be novel in the mouse. In situ hybridization analysis was carried out on 160 of the cDNAs, and of these, 29 (18%) proved to have restricted expression patterns

Dietary flavanols restore hippocampal-dependent memory in older adults with lower diet quality and lower habitual flavanol consumption

Dietary flavanols are food constituents found in certain fruits and vegetables that have been linked to cognitive aging. Previous studies suggested that consumption of dietary flavanols might specifically be associated with the hippocampal-dependent memory component of cognitive aging and that memory benefits of a flavanol intervention might depend on habitual diet quality. Here, we tested these hypotheses in the context of a large-scale study of 3,562 older adults, who were randomly assigned to a 3-y intervention of cocoa extract (500 mg of cocoa flavanols per day) or a placebo [(COcoa Supplement and Multivitamin Outcomes Study) COSMOS-Web, NCT04582617]. Using the alternative Healthy Eating Index in all participants and a urine-based biomarker of flavanol intake in a subset of participants [n = 1,361], we show that habitual flavanol consumption and diet quality at baseline are positively and selectively correlated with hippocampal-dependent memory. While the prespecified primary end point testing for an intervention-related improvement in memory in all participants after 1 y was not statistically significant, the flavanol intervention restored memory among participants in lower tertiles of habitual diet quality or habitual flavanol consumption. Increases in the flavanol biomarker over the course of the trial were associated with improving memory. Collectively, our results allow dietary flavanols to be considered in the context of a depletion–repletion paradigm and suggest that low flavanol consumption can act as a driver of the hippocampal-dependent component of cognitive aging