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My research focuses on understanding the causes, heterogeneity, inequality, and trends of population health and aging, and developing and evaluating statistical and demographic methods to interrogate the demographic, sociological, epidemiological and biological utility of various theories and conceptualizations of health and mortality. ​

It encompasses two interconnected areas: social and policy determinants of health, and population process of aging and mortality. With regard to the first, I study a broad range of social determinants of health, including macro conditions and process (e.g., income inequality, medical expansion, and one-child policy), meso environment (e.g., work environment, marriage market, household structure), and individual-level sociodemographic status (e.g., marriage, education). I am particularly interested in causality in the health production process, subgroup heterogeneity, lifelong consequences, and temporal changes of these effects. 

​​In the second area, I attempt to understand the heterogeneous and changing speed of aging and consequent morbidity and mortality patterns across the life course, birth cohorts, periods of time, and countries, as well as underlying social, epidemiological, demographic (e.g., mortality selection), and bio-behavioral (e.g., obesity) mechanisms. I have investigated  population heterogeneity and temporal trends in mortality and life span; the cohort trend of demographic and biological aging; and impact of life course dynamics of obesity on mortality. ​
​​Methodologically, I am interested in developing and evaluating statistical and demographic methods to investigate the interplay of social-epidemiological changes, population dynamics and population heterogeneity on the trends of health / mortality disparities and life expectancy gap.
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​Current projects investigate the rising health challenges in the U.S.; determinants and consequences of cognitive aging across the life course; nativity disparities in labor market, aging, and health.

Rising health challenges in the U.S.

Around the turn of the century, Americans’ health began to decline. I investigate the gender and racial differences in the long-term cohort trend in age-specific and cause-specific mortality, physiological status, mental health, and health behaviors. I find that for all gender and racial groups, physiological dysregulation has increased continuously from Baby Boomers through late-Gen X and Gen Y. Drug use is the predominant cause of elevated mortality among Baby Boomers while an innate physiological deterioration is the driving force behind the worsening health profiles of late-Gen X and Gen Y. I have attempted to understand the causes of population health and inequality through medical expansion, income inequality, and demographic mechanisms. Ongoing work takes a life-course perspective and investigates the early-life and adulthood factors behind this worsening health trend and the contextual socioeconomic, environmental and policy determinants. Other work reevaluates the “deaths of despair” narrative and comprehensively examines the trends of racial disparities in all-causes and cause-specific mortality and life expectancy by age, gender, and education.


​Nativity disparities in labor market, aging, and health

Despite immigrants’ lower socioeconomic status and less access to health care, they tend to have better health along many dimensions. In addition to possessing various health advantages, immigrants are known for facing especially challenging work environments and precarious labor market positions. With Wei-hsin Yu, this new project investigates how immigrants’ precarious labor market positions may alter their health advantages, whether job insecurity is equally detrimental to immigrants and the native-born, and which factors may intensify or attenuate the adverse consequences of precarious employment conditions. Moreover, different immigrant groups may fare differently because of their different occupational niches, earning trajectories, probabilities of success in the labor market, and health behaviors. The first paper examines the mortality consequence of unemployment among foreign-born people of various ethnoracial categories compared to the native-born population, the temporal changes in mortality consequences, and the heterogeneity in the impact of unemployment by gender and race/ethnicity. The second paper proposes a new longitudinal approach to investigate immigrants’ mortality advantage over real time and finds that immigrants enjoy a persistent survival advantage over the native-born. Ongoing work investigates immigrant morbidity-mortality paradox and the trend of Asian Americans' morbidity and mortality. 


​Determinants and consequences of cognitive aging across the life course

Many studies have reported declines in the incidence and prevalence of dementia in the United States over the last few decades, which is a by-product of changes in cognitive function later in life across birth cohorts. I reexamine the cohort trend in cognitive functioning and find it has been improving from the Greatest Generation to Late Children of Depression and War Babies, but then declines significantly beginning with Early-Baby Boomers and continuing into Mid-Baby Boomers. This pattern is observed universally across genders, race/ethnicities, education, occupation, income and wealth quartiles. The worsening cognitive functioning among Baby Boomers can be attributed to lower household wealth, lower likelihood of marriage, higher levels of loneliness, depression and psychiatric problems, and elevated cardiovascular risk factors (e.g., obesity, physical inactivity, hypertension, stroke, diabetes, and heart disease). The worsening cognitive functioning among Baby Boomers may potentially reverse past favorable trends in dementia if no effective interventions and policy responses are put in place. Ongoing work conducts a comprehensive investigation on the relative contribution of a wide range of childhood conditions and adulthood factors to cognitive functioning trajectories and the gender and racial differences therein.

Social and policy determinants of health

I investigate a broad range of social and policy determinants of health, which encompass four domains: (1) socioeconomic status and income inequality; (2) marriage and household structure; (3) medical expansion; and (4) workplace and work. ​I study the gender-specific effect of income inequality on health and bring the temporal perspective to bear on the lagged effects of income inequality on mortality, which explains the mixed findings in this contentious topic. I  also examine whether the married tend to overestimate their health and whether marriage is universally beneficial for people located in different positions of health spectrum and different propensities to marry.  Other work investigates the long-lasting effect of sex ratio at sexual maturity on male mortality (with Emma Zang) and the impact of one-child policy and sibling composition on children's obesity risk (with Wei He). My dissertation focuses on the process of medicalization. As the biomedical model becomes increasingly dominant in the explanation of health, illness, and other human problems and behavior, medicine has dramatically expanded in the last several decades in the developed countries. But how this expansion process has impacted population health is not sufficiently studied. I have investigated the process of medical expansion in the OECD countries in the last several decades, which is represented by expansions in three major components of the health care system: rising medical investment, medical professionalization/specialization, and expanded pharmaceutical industry. I study how medical expansion may affect population health and how this effect may be contingent on the level of socioeconomic development and the stage of epidemiological transition, the lay public's confidence in medicine in the era of medical expansion, and the role of consumers in this expansion process. Recently, I start another project with Vincent Roscigno and Yao Lu examining workplace and work as a social determinant of health and health disparities. Particularly, this project focuses on the dynamics of managerial practices, relationships, and statuses in the workplace, precarity and mismatch in the employment, and how these factors shape workers' physical and mental health and inequality therein.               - Freidson Outstanding Publication Award Honorable Mention from the ASA Medical Sociology Section, 2019


​Trend and heterogeneity in aging, mortality, and life span

I study population heterogeneity (at geographic level, e.g., country, and group level, e.g., race) and temporal trends (age, period, cohort) in mortality and life span. With Yang Claire Yang and Kenneth Land, I substantially extend the classical Strehler-Mildvan (SM) general theory of mortality and aging by synthesizing it with ecological demography. I study heterogeneity in the SM model and the ecological causes and implications of this heterogeneity on expected maximum survival age based on historical mortality data of 42 countries. I have also investigated the evolving mortality trend and mortality variation among developed countries over age, period and cohort in the context of cohort evolution, mortality selection, epidemiological transition and population aging. In this area, I am particularly interested in uncovering the cohort forces in the life course pattern of health, aging, and mortality. I have systematically investigated the trend of the rate of demographic aging and the rate of biological aging (i.e., senescence) across birth cohorts born since mid-18th century among 7 developed countries. I study the effects of cohort evolution and mortality selection on this trend and the implications for the study of limits on the human lifespan and evolution of aging. The joint effect of cohort evolution and mortality selection on cohort life-course mortality pattern leads me to further investigate its consequence on epidemiological transition in less developed countries and the implications on the high level of chronic diseases burden in these countries during the age of degenerative and man-made diseases. My work with Siwei Cheng uses simulation technique to generate cohort level aggregate mortality pattern from individual level mortality curve which enables me to test several fundamental hypotheses in biodemography of aging. Ongoing work focuses on the more recent trend in physiological status, mental health, cognitive functioning, morbidity, and mortality in the United States, which is described in detail in "rising health challenges in the U.S." above.


​Impact of life course dynamics of obesity on mortality

I bring population heterogeneity and life course perspectives to bear on the study of obesity impact on mortality and life expectancy. The effect of obesity is contingent on people’s health endowment and socioeconomic resources, which causes everyone to be unequally harmed by obesity. Furthermore, the timing of the transition to obesity status and duration of obesity also matter for the death outcome. My work with Dmitry Tumin and Zhenchao Qian captures heterogeneity in the body mass index (BMI) trajectories among older populations and suggests that BMI trajectories are more predictive of mortality risk than static BMI status. With Dmitry Tumin, I further study the origins of adult obesity in early life (e.g., birth region and family background). With Jonathan Dirlam, I investigate how selection biases (mortality selection bias, healthy participant effect and reverse causality) may affect the evolving impact of obesity on mortality risk over the life course. Recent work with Paola Echave, Neil Mehta and Mikko Myrskyla uses Framingham Heart Study data to further extend my earlier studies on the BMI trajectories and changing BMI compositions over the life course, especially how heterogeneities in life-long BMI trajectories are associated with mortality risk, and how the pattern evolves across generations.


​The role of selection in health production and aging process

S​election is prevalent and consequential in the population patterns of health and mortality. This project investigates the role of selection in health production and aging process over the life course and across birth cohorts. It encompasses four subprojects: (1) how selection may contribute to the evolving relationship between health and health determinants (e.g., marriage, education) over the life course, and the contingencies in this relationship across the selection spectrum; (2) how different ages of onset of obesity, weight loss, and mortality selection effects may change the population compositions of body mass index groups across the life course and impact the aggregate observed effect of obesity on mortality across age groups; (3) how mortality selection and cohort evolution mechanisms shape the rate of demographic aging, the rate of biological aging, and age-dependent mortality patterns across birth cohorts in both early and later transition countries; and (4) how changes in the level and variance of unobserved frailty over time may complicate the interpretation of cohort trends in health disparities and life expectancy, and how to evaluate bias due to selection dynamics.


​Modeling trends in health disparities and life expectancy gap

I​ bring demography and population dynamics to the study of trend in health disparities within the context of social, technological and epidemiological changes. Any historical trend in inequality of social outcomes, e.g., health, is confounded with another two related temporal factors: life course and cohort. I have developed an integrated model to filter the contributions of the above confounded factors from the temporal trend in health disparities, but this model should be broadly applicable to the study of social inequality in many different substantive contexts. Moreover, the temporal trend in inequality (e.g., health disparities) can increase or decline as a result of two distinct mechanisms: the gradient or set of differential relationships of social statuses to social outcomes can change or the composition of the population with respect to social statuses can change. Previous approach treats the gradient and composition as two independent and separate processes. But the gradient of social statuses can change because the population composition of these social groups changes (or selection effects). In other words, the changes in treatment effect estimates may partially come from the selection effect. In order to achieve unbiased estimates of the treatment effects, we need to remove the selection effect. I currently focus on evaluating the implications of changing population compositions on the cohort trends of health disparities. I am developing a semi-parametric method to mitigate lagged selection bias in trend studies. This project is funded by NCHS R03 grant (Research and Methods in Health Statistics RFA-SH-16-001)​. I am also currently developing a counterfactual simulation method to evaluate mortality selection effect in the trends of health disparities and gap in life expectancy.
Hui Zheng
Department of Sociology | The Ohio State University

106 Townshend Hall
1885 Neil Ave
Columbus, OH 43210
​zheng.64@osu.edu

© 2022 Hui Zheng