Annual Review of Public Health - Volume 40, 2019

Assessing the extent to which public health research findings can be causally interpreted continues to be a critical endeavor. In this symposium, we invited several researchers to review issues related to causal inference in social epidemiology and environmental science and to discuss the importance of external validity in public health. Together, this set of articles provides an integral overview of the strengths and limitations of applying causal inference frameworks and related approaches to a variety of public health problems, for both internal and external validity.

Social epidemiology seeks to describe and quantify the causal effects of social institutions, interactions, and structures on human health. To accomplish this task, we define exposures as treatments and posit populations exposed or unexposed to these well-defined regimens. This inferential structure allows us to unambiguously estimate and interpret quantitative causal parameters and to investigate how these may be affected by biases such as confounding. This paradigm has been challenged recently by some critics who favor broadening the exposures that may be studied beyond treatments to also consider states. Defining the exposure protocol of an observational study is a continuum of specificity, and one may choose to loosen this definition, incurring the cost of causal parameters that become commensurately more vague. The advantages and disadvantages of broader versus narrower definitions of exposure are matters of continuing debate in social epidemiology as in other branches of epidemiology.

The field of environmental health has been dominated by modeling associations, especially by regressing an observed outcome on a linear or nonlinear function of observed covariates. Readers interested in advances in policies for improving environmental health are, however, expecting to be informed about health effects resulting from, or more explicitly caused by, environmental exposures. The quantification of health impacts resulting from the removal of environmental exposures involves causal statements. Therefore, when possible, causal inference frameworks should be considered for analyzing the effects of environmental exposures on health outcomes.

Most of the clinical research conducted with the goal of improving health is not generalizable to nonresearch settings. In addition, scientists often fail to replicate each other's findings due, in part, to lack of attention to contextual factors accounting for their relative effectiveness or failure. To address these problems, we review the literature on assessment of external validity and summarize approaches to designing for generalizability. When investigators conduct systematic reviews, a critical need is often unmet: to evaluate the pragmatism and context of interventions, as well as their effectiveness. Researchers, editors, and grant reviewers can implement key changes in how they consider and report on external validity issues. For example, the recently published expanded CONSORT figure may aid scientists and potential program adopters in summarizing participation in and representativeness of a program across different settings, staff, and patients. Greater attention to external validity is needed to increase reporting transparency, improve program dissemination, and reduce failures to replicate research.

The burden of dementia continues to increase as the population ages, with no disease-modifying treatments available. However, dementia risk appears to be decreasing, and progress has been made in understanding its multifactorial etiology. The 2018 National Institute on Aging–Alzheimer's Association (NIA-AA) research framework for Alzheimer's disease (AD) defines AD as a biological process measured by brain pathology or biomarkers, spanning the cognitive spectrum from normality to dementia. This framework facilitates interventions in the asymptomatic space and accommodates knowledge that many additional pathologies (e.g., cerebrovascular) contribute to the Alzheimer's dementia syndrome. The framework has implications for how we think about risk factors for “AD”: Many commonly accepted risk factors are not related to AD pathology and would no longer be considered risk factors for AD. They may instead be related to other pathologies or resilience to pathology. This review updates what is known about causes, risk factors, and changing patterns of dementia, addressing whether they are related to AD pathology/biomarkers, other pathologies, or resilience.

The United Nations has called on all nations to take immediate actions to fight noncommunicable diseases (NCDs), which have become an increasingly significant burden to public health systems around the world. NCDs tend to be more common in developed countries but are also becoming of growing concern in low- and middle-income countries. Earth observation (EO) technologies have been used in many infectious disease studies but have been less commonly employed in NCD studies. This review discusses the roles that EO data and technologies can play in NCD research, including (a) integrating natural and built environment factors into NCD research, (b) explaining individual–environment interactions, (c) scaling up local studies and interventions, (d) providing repeated measurements for longitudinal studies including cohorts, and (e) advancing methodologies in NCD research. Such extensions hold great potential for overcoming the challenges of inaccurate and infrequent measurements of environmental exposure at the level of both the individual and the population, which is of great importance to NCD research, practice, and policy.

In recent decades, there has been remarkable growth in scientific research examining the multiple ways in which racism can adversely affect health. This interest has been driven in part by the striking persistence of racial/ethnic inequities in health and the empirical evidence that indicates that socioeconomic factors alone do not account for racial/ethnic inequities in health. Racism is considered a fundamental cause of adverse health outcomes for racial/ethnic minorities and racial/ethnic inequities in health. This article provides an overview of the evidence linking the primary domains of racism—structural racism, cultural racism, and individual-level discrimination—to mental and physical health outcomes. For each mechanism, we describe key findings and identify priorities for future research. We also discuss evidence for interventions to reduce racism and describe research needed to advance knowledge in this area.

A majority of the US adult population has one or more chronic conditions that require medical intervention and long-term self-management. Such conditions are among the 10 leading causes of mortality; an estimated 86% of the nation's $2.7 trillion in annual health care expenditures goes toward their treatment and management. Patient self-management of chronic diseases is increasingly essential to improve health behaviors, health outcomes, and quality of life and, in some cases, has demonstrated effectiveness for reducing health care utilization and the societal cost burden of chronic conditions. This review synthesizes the current state of the science of chronic disease self-management interventions and the evidence for their effectiveness, especially when applied with a systematic application of theories or models that account for a wide range of influences on behavior. Our analysis of selected outcomes from randomized controlled trials of chronic disease self-management interventions contained in 10 Cochrane systematic reviews provides additional evidence to demonstrate that self-management can improve quality of life and reduce utilization across several conditions.

Public policies play a crucial role in shaping how immigrants adapt to life in the United States. Federal, state, and local laws and administrative practices impact immigrants’ access to education, health insurance and medical care, cash assistance, food assistance, and other vital services. Additionally, immigration enforcement activities have substantial effects on immigrants’ health and participation in public programs, as well as effects on immigrants’ families. This review summarizes the growing literature on the consequences of public policies for immigrants’ health. Some policies are inclusive and promote immigrants’ adaptation to the United States, whereas other policies are exclusionary and restrict immigrants’ access to public programs as well as educational and economic opportunities. We explore the strategies that researchers have employed to tease out these effects, the methodological challenges of undertaking such studies, their varying impacts on immigrant health, and steps that can be undertaken to improve the health of immigrants and their families.

Television (TV) news, and especially local TV news, remains an important vehicle through which Americans obtain information about health-related topics. In this review, we synthesize theory and evidence on four main functions of TV news in shaping public health policy and practice: reporting events and information to the public (surveillance); providing the context for and meaning surrounding health issues (interpretation); cultivating community values, beliefs, and norms (socialization); and attracting and maintaining public attention for advertisers (attention merchant). We also identify challenges for TV news as a vehicle for improving public health, including declining audiences, industry changes such as station consolidation, increasingly politicized content, potential spread of misinformation, and lack of attention to inequity. We offer recommendations for public health practitioners and researchers to leverage TV news to improve public health and advance health equity.

In countries around the world, tobacco use, excessive alcohol consumption, and consumption of sugar-sweetened beverages (SSBs) are significant contributors to the global epidemic of noncommunicable diseases. As a consequence, they contribute, as well, to excess health care costs and productivity losses. A large and growing body of research documents that taxes specific to such products, known as excise taxes, reduce consumption of these products and thereby diminish their adverse health consequences. Although such taxation has historically been motivated primarily by revenue generation, governments are increasingly using these taxes to discourage unhealthy consumption. We review the global evidence on the impact of taxes and prices on the consumption of these products and the health and social consequences. We then evaluate arguments commonly raised against these taxes, identify best practices in excise tax policy, and conclude with a summary of the current status of tobacco, alcohol, and SSB excise taxes globally.

Exposure to ambient air pollution and noise is ubiquitous globally. A strong body of evidence links air pollution, and recently noise, to cardiovascular conditions that eventually may also affect cognition in the elderly. Data that support a broader influence of these exposures on cognitive function during aging is just starting to emerge. This review summarizes current findings and discusses methodological challenges and opportunities for research. Although current evidence is still limited, especially for chronic noise exposure, high exposure has been associated with faster cognitive decline either mediated through cerebrovascular events or resulting in Alzheimer's disease. Ambient environmental exposures are chronic and affect large populations. While they may yield relatively modest-sized risks, they nevertheless result in large numbers of cases. Reducing environmental pollution is clearly feasible, though lowering levels requires collective action and long-term policies such as standard setting, often at the national level as well as at the local level.

Mobile phones (MPs) are the most relevant source of radiofrequency electromagnetic field (RF-EMF) exposure to the brain and the salivary gland. Whether this exposure implies a cancer risk has been addressed in several case-control and few cohort studies. A meta-analysis of these studies does not show increased risks for meningioma, pituitary, and salivary gland tumors. For glioma and acoustic neuroma, the results are heterogeneous, with few case-control studies reporting substantially increased risks. However, these elevated risks are not coherent with observed incidence time trends, which are considered informative for this specific topic owing to the steep increase in MP use, the availability of virtually complete cancer registry data from many countries, and the limited number of known competing environmental risk factors. In conclusion, epidemiological studies do not suggest increased brain or salivary gland tumor risk with MP use, although some uncertainty remains regarding long latency periods (>15 years), rare brain tumor subtypes, and MP usage during childhood.

Mental health and well-being are consistently influenced—directly or indirectly—by multiple environmental exposures. In this review, we have attempted to address some of the most common exposures of the biophysical environment, with a goal of demonstrating how those factors interact with central structures and functions of the brain and thus influence the neurobiology of depression. We emphasize biochemical mechanisms, observational evidence, and areas for future research. Finally, we include aspects of contextual environments—city living, nature, natural disasters, and climate change—and call for improved integration of environmental issues in public health science, policies, and activities. This integration is necessary for reducing the global pandemic of depression.

Multiple global environmental changes (GECs) now under way, including climate change, biodiversity loss, freshwater depletion, tropical deforestation, overexploitation of fisheries, ocean acidification, and soil degradation, have substantial, but still imperfectly understood, implications for human health. Noncommunicable diseases (NCDs) make a major contribution to the global burden of disease. Many of the driving forces responsible for GEC also influence NCD risk through a range of mechanisms. This article provides an overview of pathways linking GEC and NCDs, focusing on five pathways: (a) energy, air pollution, and climate change; (b) urbanization; (c) food, nutrition, and agriculture; (d) the deposition of persistent chemicals in the environment; and (e) biodiversity loss.

Increased energy demands and innovations in upstream oil and natural gas (ONG) extraction technologies have enabled the United States to become one of the world's leading producers of petroleum and natural gas hydrocarbons. The US Environmental Protection Agency (EPA) lists 187 hazardous air pollutants (HAPs) that are known or suspected to cause cancer or other serious health effects. Several of these HAPs have been measured at elevated concentrations around ONG sites, but most have not been studied in the context of upstream development. In this review, we analyzed recent global peer-reviewed articles that investigated HAPs near ONG operations to (a) identify HAPs associated with upstream ONG development, (b) identify their specific sources in upstream processes, and (c) examine the potential for adverse health outcomes from HAPs emitted during these phases of hydrocarbon development.

Health impact assessment (HIA) is a forward-looking, evidence-based tool used to inform stakeholders and policy makers about the potential health effects of proposed projects and policies and to identify options for maximizing potential health benefits and minimizing potential harm. This review examines how health equity, a core principle of health impact assessment (HIA), has been operationalized in HIAs conducted in the United States in one sector, transportation. Two perspectives on promoting health equity appear in the broader public health research literature; one aims at reducing disparities in health determinants and outcomes in affected populations, whereas the other focuses on facilitating community participation and self-determination. Variations in how these perspectives are applied in HIA informed our typology of five ways of addressing health equity in HIA. Transportation HIAs commonly included two of these—selecting vulnerable populations for the focus of the HIA and stakeholder engagement, seen in more than 70% of the 96 HIAs reviewed. Fewer than half of the HIAs assessed current health disparities or changes in their distribution. Only 15% of HIAs addressed equity by focusing on capabilities development or empowerment. Routinely assessing and reporting how an HIA aims to address health equity might better manage expectations and could make HIA practitioners and users more conscious of how an HIA can realistically be used to advance health equity.

Food insecurity affects 1 in 8 US households and has clear implications for population health disparities. We present a person-centered, multilevel framework for understanding how individuals living in food-insecure households cope with inadequate access to food themselves and within their households, communities, and broader food system. Many of these coping strategies can have an adverse impact on health, particularly when the coping strategies are sustained over time; others may be salutary for health. There exist multiple opportunities for aligning programs and policies so that they simultaneously support food security and improved diet quality in the interest of supporting improved health outcomes. Improved access to these programs and policies may reduce the need to rely on individual- and household-level strategies that may have negative implications for health across the life course.

Research into the relationship between happiness and health is developing rapidly, exploring the possibility that impaired happiness is not only a consequence of ill-health but also a potential contributor to disease risk. Happiness encompasses several constructs, including affective well-being (feelings of joy and pleasure), eudaimonic well-being (sense of meaning and purpose in life), and evaluative well-being (life satisfaction). Happiness is generally associated with reduced mortality in prospective observational studies, albeit with several discrepant results. Confounding and reverse causation are major concerns. Associations with morbidity and disease prognosis have also been identified for a limited range of health conditions. The mechanisms potentially linking happiness with health include lifestyle factors, such as physical activity and dietary choice, and biological processes, involving neuroendocrine, inflammatory, and metabolic pathways. Interventions have yet to demonstrate substantial, sustained improvements in subjective well-being or direct impact on physical health outcomes. Nevertheless, this field shows great potential, with the promise of establishing a favorable effect on population health.