Findings

Relatively well

Kevin Lewis

November 20, 2018

Priorities for Preventive Action: Explaining Americans’ Divergent Reactions to 100 Public Risks
Jeffrey Friedman
American Journal of Political Science, forthcoming

Abstract:
Why do Americans’ priorities for combating risks like terrorism, climate change, and violent crime often seem so uncorrelated with the dangers that those risks objectively present? Many scholars believe the answer to this question is that heuristics, biases, and ignorance cause voters to misperceive risk magnitudes. By contrast, this article argues that Americans’ risk priorities primarily reflect judgments about the extent to which some victims deserve more protection than others and the degree to which it is appropriate for government to intervene in different areas of social life. The article supports this argument with evidence drawn from a survey with 3,000 respondents, using pairwise comparisons to elicit novel measures of how respondents perceive nine dimensions of 100 life‐threatening risks. Respondents were well informed about these risks’ relative magnitudes — the correlation between perceived and actual mortality was .82 — but those perceptions explained relatively little variation in policy preferences relative to judgments about the status of victims and the appropriate role of government. These findings hold regardless of political party, education, and other demographics. The article thus argues that the key to understanding Americans’ divergent reactions to risk lies more with their values than with their grasp of factual information.


Increased frequency of travel may act to decrease the chance of a global pandemic
Robin Thompson et al.
University of Oxford Working Paper, August 2018

Abstract:
The high frequency of modern travel has led to concerns about a devastating pandemic since a lethal pathogen strain could spread worldwide quickly. Many historical pandemics have arisen following pathogen evolution to a more virulent form. However, some pathogen strains invoke immune responses that provide partial cross-immunity against infection with related strains. Here, we consider a mathematical model of successive outbreaks of two strains: a low virulence strain outbreak followed by a high virulence strain outbreak. Under these circumstances, we investigate the impacts of varying travel rates and cross-immunity on the probability that a major epidemic of the high virulence strain occurs, and the size of that outbreak. Frequent travel between subpopulations can lead to widespread immunity to the high virulence strain, driven by exposure to the low virulence strain. As a result, major epidemics of the high virulence strain are less likely, and can potentially be smaller, with more connected subpopulations. Cross-immunity may be a factor contributing to the absence of a global pandemic as severe as the 1918 influenza pandemic in the century since.


The Cost of Convenience: Ridesharing and Traffic Fatalities
John Barrios, Yael Hochberg & Livia Hanyi Yi
University of Chicago Working Paper, September 2018

Abstract:
We examine the effect of the introduction of ridesharing services in U.S. cities on fatal traffic accidents. The arrival of ridesharing is associated with an increase of 2-3% in the number of motor vehicle fatalities and fatal accidents. This increase is not only for vehicle occupants, but also for pedestrians. We propose a simple conceptual model to explain the effects of ridesharing’s introduction on accident rates. Consistent with the notion that ridesharing increases congestion and road utilization, we find that the introduction of ridesharing is associated with an increase in arterial vehicle miles traveled, excess gas consumption, and annual hours of delay in traffic. On the extensive margin, ridesharing arrival is also associated with an increase in new car registrations. These effects are higher in cities with higher ex-ante use of public transportation and carpools, consistent with a substitution effect, and in larger cities and cities with high ex-ante vehicle ownership. The increase in accidents appears to persist (and even increase) over time. Back-of-the-envelope estimates of the annual cost in human lives range from $5.33 billion to $13.24 billion per year.


Are Some Neighborhoods Bad For Your Waistline? A Test of Neighborhood Exposure Effects on BMI
Susan Ou
Journal of Health Economics, January 2019, Pages 52-63

Abstract:
I study the causal impact of neighborhoods on body mass index (BMI). Through exploiting variation in the number of years individuals have lived in their neighborhood, using a data set from California, I examine if there exist causal effects of exposure to neighborhoods with high potential effects on one's BMI. The identifying assumption is that there are no unobserved individual level characteristics correlated with both BMI and moving, after controlling for observables. I find evidence that suggests that neighborhoods do not have a causal impact on BMI.


The impact of 1998 Massachusetts gun laws on suicide: A synthetic control approach
Leo Kahane & Peter Sannicandro
Economics Letters, forthcoming

Abstract:
In 1998 Massachusetts enacted nearly two dozen gun laws. Using the synthetic control method, we find evidence that these laws led to reduced overall suicide rates for several years, and a sustained reduction in suicides carried out with a firearm.


Decomposing the causes of the socioeconomic status-health gradient with biometrical modeling
Mason Garrison & Joseph Lee Rodgers
Journal of Personality and Social Psychology, forthcoming

Abstract:
The consistent relationship between socioeconomic status (SES) and health has been widely covered in the media and scientific journals, which typically argue that physical-health inequalities are caused by material disadvantage directly or indirectly (e.g., chronic environmental-stress, health care resources, etc.). Such explanations do not explain the finely stratified health differences across the entire range of SES. Recent theories have helped address such limitations, but implicate multiple different explanatory pathways. For example, differential epidemiology articles have argued that individual differences are the “fundamental cause” of the gradient (Gottfredson, 2004). Alternatively, variants of allostatic load theory (McEwen & Stellar, 1993), such as the Risky Families model (Repetti, Taylor, & Seeman, 2002) implicate the early home-environment. These theory-driven pathways align with interpretations associated with biometrical models; yet, little research has applied biometrical modeling to understanding the sources of the gradient. Our study presents several innovations and new research findings. First, we use kinship information from a large national family dataset, the NLSY79, whose respondents are approximately representative of United States adolescents in 1979. Second, we present the first biometrical analysis of the relationships between SES and health that uses an overall SES measure. Third, we separate physical and mental health, using excellent measurement of each construct. Fourth, we use a bivariate biometrical model to study overlap between health and SES. Results suggest divergent findings for physical and mental health. Biometrical models indicate a primarily genetic etiology for the link between SES and physical health, and a primarily environmental etiology for the link between SES and mental health.


Long‐chain polyunsaturated fatty acid supplementation in the first year of life affects brain function, structure, and metabolism at age nine years
Rebecca Lepping et al.
Developmental Psychobiology, forthcoming

Abstract:
The present study sought to determine whether supplementation of long‐chain polyunsaturated fatty acids (LCPUFA) during the first year of life influenced brain function, structure, and metabolism at 9 years of age. Newborns were randomly assigned to consume formula containing either no LCPUFA (control) or formula with 0.64% of total fatty acids as arachidonic acid (ARA; 20:4n6) and variable amounts of docosahexaenoic acid (DHA; 22:6n3) (0.32%, 0.64%, or 0.96% of total fatty acids) from birth to 12 months. At age 9 years (±0.6), 42 children enrolled in a follow‐up multimodal magnetic resonance imaging (MRI) study including functional (fMRI, Flanker task), resting state (rsMRI), anatomic, and proton magnetic resonance spectroscopy (1H MRS). fMRI analysis using the Flanker task found that trials requiring greater inhibition elicited greater brain activation in LCPUFA‐supplemented children in anterior cingulate cortex (ACC) and parietal regions. rsMRI analysis showed that children in the 0.64% group exhibited greater connectivity between prefrontal and parietal regions compared to all other groups. In addition, voxel‐based analysis (VBM) revealed that the 0.32% and 0.64% groups had greater white matter volume in ACC and parietal regions compared to controls and the 0.96% group. Finally, 1H MRS data analysis identified that N‐acetylaspartate (NAA) and myo‐inositol (mI) were higher in LCPUFA groups compared to the control group. LCPUFA supplementation during infancy has lasting effects on brain structure, function, and neurochemical concentrations in regions associated with attention (parietal) and inhibition (ACC), as well as neurochemicals associated with neuronal integrity (NAA) and brain cell signaling (mI).


Availability and Accessibility of Emergency Contraception to Adolescent Callers in Pharmacies in Four Southwestern States
Jasmine Uysal et al.
Journal of Adolescent Health, forthcoming

Methods: Using a mystery-caller approach, we trained male and female data collectors to phone pharmacies posing as 16-year-olds who wanted to prevent a pregnancy after recent unprotected sex. From April to May 2016, they called 1,475 randomly selected retail pharmacies in Arizona, California, New Mexico, and Utah and completed an online survey about their experience. Caller data were analyzed by state and pharmacy type (i.e., national chains, regional outlets, and individually owned outlets).

Results: Of pharmacies contacted, 80.6% had EC available at the time of the call. Availability of EC varied by state (p < .01) and pharmacy type (p < .01), but not by rural/urban location. Even where EC was available, pharmacy personnel often hindered youths’ access to EC by mentioning incorrect point-of-sale restrictions, keeping EC in restrictive store locations, or asking personal questions. Individually owned outlets presented significantly more barriers than larger chains. Overall, EC was completely accessible to an adolescent caller in only 28% of pharmacies. Lower EC accessibility was found in states with higher teen pregnancy rates.


Elevated pro-inflammatory gene expression in the third trimester of pregnancy in mothers who experienced stressful life events
Kharah Ross et al.
Brain, Behavior, and Immunity, forthcoming

Methods: A sample of 116 low-income, diverse women was recruited from 5 U.S. sites by the Community Child and Health Network at the birth of a child. This study is of the subgroup of women who became pregnant again over the two-year follow-up period, and provided information on stressful life events that occurred both preconception and during the third trimester of the subsequent pregnancy. Dried blood spots (DBS) were collected in the third trimester of pregnancy, and used for gene expression analysis.

Results: Women with more prenatal stressful life events had higher expression of pro-inflammatory genes when compared to those with fewer life events, and the effect was driven by increased activation of pro-inflammatory transcription factors, NF-κB and AP-1. Preconception stressful life event exposure was not associated with gene expression profiles. When entered into models simultaneously, only prenatal stressful life events were associated with up-regulation of pro-inflammatory genes. No differences between high or low stress groups emerged for antiviral or antibody genes.


Longevity and sexual maturity vary across species with number of cortical neurons, and humans are no exception
Suzana Herculano‐Houzel
Journal of Comparative Neurology, forthcoming

Abstract:
Maximal longevity of endotherms has long been considered to increase with decreasing specific metabolic rate, and thus with increasing body mass. Using a dataset of over 700 species, here I show that maximal longevity, age at sexual maturity and post‐maturity longevity across bird and mammalian species instead correlate primarily, and universally, with the number of cortical brain neurons. Correlations with metabolic rate and body mass are entirely explained by clade‐specific relationships between these variables and numbers of cortical neurons across species. Importantly, humans reach sexual maturity and subsequently live just as long as expected for their number of cortical neurons, which eliminates the basis for earlier theories of protracted childhood and prolonged post‐menopause longevity as derived human characteristics. Longevity might increase together with numbers of cortical neurons through their impact on three main factors: delay of sexual maturity, which postpones the onset of aging; lengthening of the period of viable physiological integration and adaptation, which increases post‐maturity longevity; and improved cognitive capabilities that benefit survival of the self and of longer‐lived progeny, and are conducive to prolonged learning and cultural transmission through increased generational overlap. Importantly, the findings indicate that theories of aging and neurodegenerative diseases should take absolute time lived besides relative “age” into consideration.


Estimates of the Heritability of Human Longevity Are Substantially Inflated due to Assortative Mating
Graham Ruby et al.
Genetics, November 2018, Pages 1109-1124

Abstract:
Human life span is a phenotype that integrates many aspects of health and environment into a single ultimate quantity: the elapsed time between birth and death. Though it is widely believed that long life runs in families for genetic reasons, estimates of life span “heritability” are consistently low (∼15–30%). Here, we used pedigree data from Ancestry public trees, including hundreds of millions of historical persons, to estimate the heritability of human longevity. Although “nominal heritability” estimates based on correlations among genetic relatives agreed with prior literature, the majority of that correlation was also captured by correlations among nongenetic (in-law) relatives, suggestive of highly assortative mating around life span-influencing factors (genetic and/or environmental). We used structural equation modeling to account for assortative mating, and concluded that the true heritability of human longevity for birth cohorts across the 1800s and early 1900s was well below 10%, and that it has been generally overestimated due to the effect of assortative mating.


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