Introduction

Life course epidemiology aims to explore the factors influencing health at different stages throughout the entire life span, from birth to death. The sensitive period model and the cumulative model reveal the roles of various risk factors in the occurrence and development of diseases. The sensitive period model emphasizes that early life exposures can affect the development of various body systems, thereby having long-term health impacts (Figure 1). The cumulative model focuses on the cumulative effects of various risk factors over an individual's life span, highlighting the harm of continuous exposure to multiple adverse factors on long-term health. Dr. Jufen Liu and her research team from School of Public Health, Peking University, have long focused on adverse early life exposures from different sources using the sensitive period and cumulative models. They explore the associations between these exposures and the risks of diseases and health levels in middle-aged and old adults. Additionally, the team also pays attention to interventions for adverse early life exposures. Their research results can provide population evidence for the construction of healthy aging and are of great significance for the formulation of health policies that cover the entire life course.

Figure 1. Relationship Diagram of Early Life Adverse exposures, Health Outcomes and Effective Intervention Strategies

Series Ⅰ: Depressive and cognitive trajectories and the risk of dementia and death in older adults

First Affiliation: Peking University

First author: Ziyang Ren

Corresponding author: Jufen Liu

Journal: General Psychiatry, IF2022 = 11.9

Citation: Ren Z, Nie L, Du Y, Liu J*. Intertwined depressive and cognitive trajectories and the risk of dementia and death in older adults: a competing risk analysis. Gen Psychiatr. 2024;37:e101156. doi:10.1136/gpsych-2023-101156

Full Text Links: https://pubmed.ncbi.nlm.nih.gov/38616970/

To explore the impact of the intertwined trajectories of depressive symptoms and cognitive function on the risk of dementia and mortality in the old adults, Dr. Jufen Liu and her research team from School of Public Health, Peking University, conducted an in-depth analysis using data from the Health and Retirement Study (HRS) in the United States. The study found a significant interaction between depressive symptoms and cognitive function in relation to the risk of developing dementia, particularly among women. Specifically, individuals with rapidly declining cognitive function but lower depressive symptoms had a risk of all-cause dementia and mortality comparable to or higher than those with persistently high depressive symptoms and cognitive impairment. This finding underscores the importance of early identification and management of mental health and cognitive differences in the prevention of dementia and mortality among old adults.

Series Ⅱ: Adverse childhood experiences and risk of depressive symptoms and cognitive impairment

First Affiliation: Peking University

First author: Ziyang Ren

Corresponding author: Jufen Liu, Xiaoying Zheng

Journal: General Psychiatry, IF2022 = 11.9

Citation: Ren Z, Luo Y, Zheng X*, Liu J*. Adverse childhood experiences from family and society contribute to increased risk of depressive symptoms and cognitive impairment: a cross-sectional study. Gen Psychiatr. 2023 Sep 7;36(4):e101039. doi: 10.1136/gpsych-2023-101039.

Full Text Links:https://pubmed.ncbi.nlm.nih.gov/37705929/

To investigate how childhood adversity from family and social sources affects the risk of depressive symptoms and cognitive impairment in middle-aged and old adults Chinese populations, Dr.Jufen Liu and her research team from School of Public Health, Peking University, utilized data from the China Health and Retirement Longitudinal Study (CHARLS). The study found significant associations between childhood adversity within the family and society and both depressive symptoms and cognitive function. Additionally, the research advocates for raising the average education level across the population to prevent depressive symptoms and cognitive impairment resulting from childhood adversity. This study provides population evidence for a sociological perspective on understanding childhood adversity and developing effective prevention and intervention strategies.

Series Ⅲ: BMI transition and trajectory modify the associations of adverse childhood experiences with new-onset dementia

First Affiliation: Peking University

First author: Ziyang Ren, Binbin Su

Corresponding author: Jufen Liu, Xiaoying Zheng

Journal: General Psychiatry, IF2022 = 11.9

Citation: Ren Z#, Su B#, Du Y, Zhou T, Zheng X*, Liu J*. Effect modifications of BMI transition and trajectory in the associations of adverse childhood experiences with new-onset dementia and its subtypes in older US adults. Gen Psychiatr. 2023 Aug 22;36(4):e101092. doi: 10.1136/gpsych-2023-101092.

Full Text Links:https://www.sciencedirect.com/science/article/pii/S0160412019339364

To explore the association between childhood adversity and the onset of dementia and its subtypes in the old adults, Dr. Jufen Liu and her research team from School of Public Health, Peking University, used data from the Health and Retirement Study (HRS) in the United States. They analyzed the impact of six types of childhood adversity (emotional neglect, parental substance abuse, physical abuse, economic adversity, grade retention, and delinquency) on all-cause dementia and Alzheimer's disease. The study found a significant interaction between childhood adversity and long-term changes in body mass index (BMI). Specifically, individuals who maintained a higher BMI had a lower risk of dementia and Alzheimer's disease compared to those whose BMI remained within the normal range. This finding highlights the importance of integrating weight management to prevent the increased risk of dementia associated with childhood adversity.

Series Ⅳ: Internet use and multimorbidity, and death in older adults

First Affiliation: Peking University

First author: Ziyang Ren

Corresponding author: Jufen Liu

Journal: Global Health, IF2022 = 10.8

Citation: Ren Z, Xia S, Sun J, Wang D, Du Y, Li N, Liu J*. Internet use, cardiometabolic multimorbidity, and death in older adults: a multi-cohort study spanning developing and developed countries. Global Health. 2023 Nov 6;19(1):81. doi: 10.1186/s12992-023-00984-z.

Full Text Links: https://pubmed.ncbi.nlm.nih.gov/37932770/

To explore the association between internet use and the risk of cardiovascular metabolic diseases and mortality in the old adults, Dr. Jufen Liu and her research team from School of Public Health, Peking University, utilized data from four globally comparable longitudinal studies from China, Mexico, the United States, and Europe (CHARLS, MHAS, HRS, SHARE). The study indicates a significant negative correlation between internet use and the risk of incident cardiovascular metabolic diseases (heart disease, stroke, and diabetes) and mortality, particularly evident in developed countries. Additionally, the reduction in depressive symptoms partially mediated the relationship between internet use and the risk of cardiovascular metabolic diseases and mortality. These findings underscore the need to balance internet use, socioeconomic status, and health literacy when promoting internet use among the old adults, especially in developing countries. This research provides valuable insights into reducing the risk of cardiovascular metabolic diseases and mortality by improving mental health and cognitive function.

Series Ⅴ: Adverse childhood experiences and depressive symptoms and somatic conditions in older adults

First Affiliation: Peking University

First author: Ziyang Ren

Corresponding author: Jufen Liu

Journal: Social Science & Medicine, IF2022 = 5.4

Citation: Ren Z, Du Y, Lian X, Luo Y, Zheng X, Liu J*. Bidirectional longitudinal associations between depressive symptoms and somatic conditions after adverse childhood experiences in middle-aged and older Chinese: a causal mediation analysis. Soc Sci Med. 2023;338: 116346. doi: 10.1016/j.socscimed.2023.116346

Full Text Links:https://www.sciencedirect.com/science/article/abs/pii/S0277953623007037

To explore the bidirectional long-term effects of adverse childhood experiences on depressive symptoms and physical ailments in middle-aged and old adults individuals, Dr. Jufen Liu and her research team from School of Public Health, Peking University, utilized data from the China Health and Retirement Longitudinal Study (CHARLS) to analyze the detailed connections between these factors. The study found that adverse childhood experiences significantly increased the risk of experiencing pain, falls, chronic diseases, multimorbidity, as well as limitations in activities of daily living and instrumental activities of daily living. Adverse childhood experiences further exacerbated these effects through the mediating role of depressive symptoms. The research highlights the mutually reinforcing bidirectional relationship between depressive symptoms and physical ailments, suggesting that future prevention strategies should prioritize mental health to mitigate the negative impact of adverse childhood experiences on the health of the old adults. This finding is particularly important for countries like China, with limited healthcare resources and widespread adverse childhood experiences.

Series Ⅵ Healthy lifestyles reduce risk of depressive symptoms attributed to life-course disadvantages among older adults

First Affiliation: Peking University

First author: Ziyang Ren

Corresponding author: Jufen Liu, Xiaoying Zheng

Journal: Journal of Affective Disorders, IF2022 = 6.6

Citation: Ren Z, Du Y, Lian X, Sun J, Zheng X*, Liu J*. The dilution effects of healthy lifestyles on the risk of depressive symptoms attributed to life-course disadvantages among Chinese middle-aged and older adults. J Affect Disord. 2023 Sep 1;336:97-105. doi: 10.1016/j.jad.2023.05.064. Epub 2023 May 26. PMID: 37245546

Full Text Links: https://pubmed.ncbi.nlm.nih.gov/37245546/

To explore the attenuating effect of healthy lifestyle on depression symptoms resulting from life course adversity, Dr. Jufen Liu and her research team from School of Public Health, Peking University, utilized data from the China Health and Retirement Longitudinal Study to investigate the associations among these factors in middle-aged and old adults individuals. The study findings indicate that healthy lifestyle choices, such as regular exercise, adequate sleep, non-smoking, and moderate alcohol consumption, significantly reduce the risk of depression symptoms resulting from life course adversity. As the cumulative level of life course adversity increases, the positive impact of a healthy lifestyle becomes more pronounced. Additionally, the study found that adequate sleep and non-smoking play crucial roles in alleviating depression symptoms. The research calls for the promotion and dissemination of healthy lifestyles among middle-aged and old adults to reduce their risk of experiencing depression symptoms.

Series Ⅶ Impact of adverse childhood experiences on life expectancy

First Affiliation: Peking University

First author: Yushan Du, Yanan Luo

Corresponding author: Jufen Liu

Journal: Child Abuse & Neglect, IF2022 = 4.8

Citation: Du Y#, Luo Y#, Ren Z, Zheng X, Liu J*. Impact of adverse childhood experiences on life expectancy with depression in the UK population: the mitigating role of educational attainment. Child Abuse & Neglect, 2023, 144: 106383. doi: 10.1016/j.chiabu.2023.106383.

Full Text Links: https://pubmed.ncbi.nlm.nih.gov/37541093/

Adverse childhood experiences are associated with depression-adjusted life expectancy, and higher levels of education may mitigate the long-term adverse effects of adverse childhood experiences on mental health. Using multi-state life table methods, the study analyzed the impact of adverse childhood experiences on depression-adjusted life expectancy in middle-aged and older adults, as well as the mediating effect of education. The results revealed that adverse childhood experiences were associated with longer depression-adjusted life expectancy, with women who experienced adverse childhood experiences having longer depression-adjusted life expectancy compared to men. Higher levels of education may mitigate the impact of adverse childhood experiences on depression-adjusted life expectancy, with younger victims of adverse childhood experiences potentially deriving more health benefits from education.

Series Ⅷ Number of children and cognitive function in mid-life

First Affiliation: Peking University

First author: Yushan Du, Yanan Luo

Corresponding author: Jufen Liu

Journal: Journal of Affective Disorders，IF2022 = 6.6

Citation: Du Y#, Luo Y#, Zheng X, Liu J*. Number of children and cognitive function among Chinese menopausal women: The mediating role of depressive symptoms and social participation. Journal of Affective Disorders, 2023, 340: 758-765. doi: 10.1016/j.jad.2023.08.084.

Full Text Links: https://pubmed.ncbi.nlm.nih.gov/37591349/

Fertility history is related to cognitive function in older women, with depressive symptoms and social activities playing mediating roles. The study found that a higher number of biological children is associated with poorer cognitive function in postmenopausal women, and this association is more significant in urban postmenopausal women compared to their rural counterparts. The detrimental effect of the number of biological children on cognitive function may be mediated by women's depressive symptoms and social activities. The findings emphasize the potential benefits of promoting the psychological and social health of women with more children for their cognitive function in old age.

Summary and Outlook

Adverse exposures in early life can cause long-term harm to health across various stages of an individual's life. Promoting population health from a life course perspective involves exploring social, environmental, and behavioral risk factors that affect health throughout the life span. This is crucial for developing health policies that cover the entire life cycle. In the future, the research team will continue to leverage large cohort data and derived data resources from multiple countries. They will collaborate with domestic and international scholars to conduct interdisciplinary, integrated, and systematic research, focusing on the development of multi-source big data and methodological research. This will reveal related risk factors and pathogenic mechanisms of early-life adverse exposures, providing foundational evidence and tools for developing population-level health interventions across the life span and promoting policy and practice translation.

Author Biography

Corresponding author

Dr. Jufen Liu, Assistant professor (Tenure Track), Institute of Reproductive and Child Health, School of Public Health, Peking University.

Dr. Jufen Liu lead her research to investigate the early life determinants and trajectories of chronic diseases throughout the life course, through which to develop population level interventions to prevent chronic diseases and multimorbidity, as well as to support translation of discovery into policy and practice both within in China and in the global community. She has a broad interest in birth defects and disability, focusing on neurodevelopmental disorders, degenerative diseases, chronic diseases and multi-morbidities at all ages. She has led on original research articles and her publications are featured in journals such as International Journal of Epidemiology, eClinicalMedicine, Social Science and Medicine, Globalization and Health, General Psychiatry, Chinese Journal of Epidemiology, Chinese Journal of Preventive Medicine, and so forth. Her research has been recognized with awards from Huaxia Medical Science and Technology Assiociation, Chinese Preventive Medicine Association, Beijing Preventive Medicine Association and Ministry of Education, China. Dr Liu served as scientific communities, she is a standing committee member of the China Maternal and Child Health Association's Professional Committee on Perinatology and Metabolism; a member of the Chinese Preventive Medicine Association's Professional Committee on Birth Defects Prevention and Control, and the Committee on Family-School-Community Education of the Chinese Family Education Society. She is also served in the editorial boards of academic journals, including Reproductive Health (Deputy Editor), BMC Pregnancy and Childbirth (Editorial Board Member), China CDC Weekly (Guest Editor), Frontiers in Nutrition (Guest Editor), Nutrients (Guest Editor), and China Journal of Reproductive Health (Editor).

Ziyang Ren, Ph.D. Candidate, Institute of Reproductive and Child Health, School of Public Health, Peking University.

Research Interests: Application of life course epidemiology in the study of middle-aged and older adults’ health. To date, several papers have been published as the first author in eClinicalMedicine (Impact Factor = 15.1), JAMA Network Open (Impact Factor = 13.8), General Psychiatry (Impact Factor = 11.9), and Globalization and Health (Impact Factor = 10.8).

Yushan Du, Master student of Public Health, Institute of Reproductive and Child Health, School of Public Health, Peking University.

Research Interests: Social epidemiology. To date, five papers have been published as the first author or co-first author in Journal of Affective Disorders (Impact Factor = 6.6), Nutrients (Impact Factor = 5.9), Child Abuse & Neglect (Impact Factor = 4.8), Nutrition Research (Impact Factor = 4.5), and the International Journal of Environmental Health Research (Impact Factor = 3.2). She received the Peking University Outstanding Research Award for the 2022-2023 academic year.

Duoduo Wang, Master student of Public Health, Institute of Reproductive and Child Health, School of Public Health, Peking University.

Research Interests: Screen exposure and early development among children. To date, two papers have been published as the first author in Journal of International AIDS Society (Impact Factor = 6), China CDC Weekly (Impact Factor = 4.7), She joined one of the Family Education Research Project of China Family Education Association (2021-2025) which studied the Relationship between Preschool Children's Screen Exposure, Family Rearing Environment, and Child Behavioral Development.

Lirong Nie, Master student of Public Health, Institute of Reproductive and Child Health, School of Public Health, Peking University.

Research Interests: Folic acid and birth defects. To date, three papers have been published as co-author in General Psychiatry (Impact Factor = 11.9), Journal of Affective Disorders (Impact Factor = 6.6), and Nutrients (Impact Factor = 5.9).

Dr. Yanan Luo, from School of Public Health, Peking University; Dr. Ning Li, from Institute of Population Research, Peking University; Dr. Jinfang Sun, from Chinese Centre for Disease Control and Prevention, and Prof. Xiaoying Zheng, from School of Population Medicine and Public Health, Chinese Academy of Medical Sciences/Peking Union Medical College made significant contribution to this study.

Contributed by | Dr. Jufen Liu and her research team (Peking University)

Reviewed by | ExposomeX Team

Institute Introduction

Peking University Institute of Reproductive and Child Health

Peking University Institute of Reproductive and Child Health mainly focus on the research areas of reproductive health epidemiology, environment and reproductive health, and translational research in reproductive health studies. It particularly focuses on the distribution patterns, influencing factors, mechanisms of disease, and prevention strategies for adverse reproductive health outcomes, utilization of big data in reproductive health, application of artificial intelligence, and related interdisciplinary transformations. The institute serves as the direct support unit for the NHC Key Laboratory of Reproductive Health (Peking University) and is specifically responsible for the National Office for Maternal and Child Health Annual Report. Its achievements have been published in top international journals with the faculties as the first or corresponding authors, such as NEJM, Lancet, JAMA, BMJ, Cell, PNAS, Science Bulletin, JAMA subsidiaries, Lancet subsidiaries, Science subsidiaries, Nature subsidiaries, The Innovation, Environ Health Perspect, Int J Epidemiol, Environ Sci Technol, etc. It also hosts the core Chinese scientific journal "Chinese Journal of Reproductive Health" (Website: http://cjrh.bjmu.edu.cn/).

The outstanding talents at home and abroad are welcome for seeking job and build dream here. Contacts: Dr. Bin Wang, Vice Dean of Institute of Reproductive and Child Health of Peking University. Main page: https://sph.pku.edu.cn/info/1442/4225.htm