Research Initiatives

PHS stimulates research initiatives in the following areas. Some initiatives represent new directions for ongoing collaborations while others are in every sense new. Contact us for more information about any of the initiatives or to be connected with the investigators.

Sources of Variation in Under-5 Mortality across Sub-Saharan Africa: A Spatial Analysis

Detailed spatial understanding of levels and trends in under-5 mortality is needed to improve the targeting of interventions to the areas of highest need, and to understand the sources of variation in mortality. To improve this understanding, we analysed local-level information on child mortality across sub-Saharan Africa between 1980–2010.  We used data from 82 Demographic and Health Surveys in 28 sub-Saharan African countries, including the location and timing of 3·24 million childbirths and 393 685 deaths, to develop high-resolution spatial maps of under-5 mortality in the 1980s, 1990s, and 2000s. These estimates were at a resolution of 0·1 degree latitude by 0·1 degree longitude (roughly 10 km × 10 km). We then analysed this spatial information to distinguish within-country versus between-country sources of variation in mortality, to examine the extent to which declines in mortality have been accompanied by convergence in the distribution of mortality, and to study localised drivers of mortality differences, including temperature, malaria burden, and conflict.

Our findings suggest that sub-national determinants explain a greater portion of under-5 mortality than do country-level characteristics. Sub-national measures of child mortality could provide a more accurate, and potentially more actionable, portrayal of where and why children are still dying than can national statistics. You can read the full article here.

Interdisciplinary Approaches to Study Wildfire-induced Cardiovascular and Lung Disease

Air pollution exposure is associated with an increase in cardiovascular disease and stroke. The unfortunate increase in wildfires in association with climate change has only augmented the impact of air pollution on health in many areas of the country.  Given that wildfires can also affect asthma and respiratory disorders through deleterious activation of the immune system, we will focus our study on the impacts that wildfires have on the proinflammatory effects on the respiratory and cardiovascular systems. Given that prescribed burns could be one of the solutions to mitigate the intensity and spread of wildfires, we propose to compare health effects in a well-studied population in the Central Valley of CA (specifically, Fresno) exposed to many wildfires vs. prescribed burns over the last nine years for which our group has already collected blood samples and extensive health data.  

We have assembled a multi-disciplinary team of experts (Mark Cullen, Francois Haddad, Kari Nadeau, Mary Prunicki and Joseph Wu), from widely disparate fields to combine basic science, clinical, population health, policy, and translational research. The specific aims, projects, and approaches are integrated so that none of the scientific objectives could be achieved without the efforts of the multidisciplinary teams.  If the specific aims of this proposal are met, we will be able to not only understand the biological effects of wildfires vs prescribed burns on inflammatory pathways but also link public health effects of wildfires vs prescribed burns to potential policy changes to mitigate wildfire-induced diseases.  To learn more about this project, please email Linda Walker.

Occupational Exposure to PM2.5 and Cardiovascular Disease(CVD)

Increased risk of cardiovascular disease (CVD) related to particulate matter (PM) in air pollution has become a major public health concern in the US and worldwide. However, while exposure to particles of combustion and crustal origin are prevalent in industrial work, in concentrations up to 2-3 orders of magnitude higher than those associated with CVD in the ambient environment, evidence regarding occupational-related heart disease risk associated with PM exposure is scant. We propose to examine CVD incidence and mortality in a cohort of approximately 75,000 workers exposed to PM2.5 of varying composition and concentration, who has been under intense observation for over a decade as part of the PI's ongoing studies at a major Aluminum Company. As a consequence of these ongoing studies, the investigators have in-hand and fully linked unparalleled information on individual social (e.g. income, education, savings) and behavior (e.g. smoking, BMI, cholesterol) risks, work exposure profiles including all physical, chemical and psycho-social factors of relevance (e.g. heat, noise, strain), complete health claims files since 1996, and NDI results through 2007.

Millions of American workers are exposed to fine particulate in the workplaces. Although there is accumulating evidence such exposures may cause cardiovascular disease, fine particulate has not generally been measured in the workplace, nor directly regulated or uncontrolled. Thus, cardiovascular risk remains unknown. This proposal aims to provide such information in a major industrial setting with broad relevance to the US working population.

Robust Relationship Between Air Quality and Infant Mortality in Africa

Poor air quality is thought to be an important mortality risk factor globally, but there is little direct evidence from the developing world on how mortality risk varies with changing exposure to ambient particulate matter. Current global estimates apply exposure-response relationships that have been derived mostly from wealthy, mid-latitude countries to spatial population data 4, and these estimates remain unvalidated across large portions of the globe.

Here we combine household survey-based information on the location and timing of nearly 1 million births across sub-Saharan Africa with satellite-based estimates 5 of exposure to ambient respirable particulate matter with an aerodynamic diameter less than 2.5mum (PM2.5) to estimate the impact of air quality on mortality rates among infants in Africa. We find that a 10 mugm-3 increase in PM2.5 concentration is associated with a 9% (95% confidence interval, 4-14%) rise in infant mortality across the dataset. This effect has not declined over the last 15 years and does not diminish with higher levels of household wealth.

Our estimates suggest that PM2.5 concentrations above minimum exposure levels were responsible for 22% (95% confidence interval, 9-35%) of infant deaths in our 30 study countries and led to 449,000 (95% confidence interval, 194,000-709,000) additional deaths of infants in 2015, an estimate that is more than three times higher than existing estimates that attribute death of infants to poor air quality for these countries 2,6. Upward revision of disease-burden estimates in the studied countries in Africa alone would result in a doubling of current estimates of global deaths of infants that are associated with air pollution, and modest reductions in African PM2.5 exposures are predicted to have health benefits to infants that are larger than most known health interventions. Please read the published article here.