Table 1 Summary of the most frequently cited references (1800–2018) in health equity studies

1

Chadwick E. Report on the Sanitary Condition of the Labouring Population of Great Britain: supplementary report on the results of special inquiry into the practice of interment in towns (Vol. 1). HM Stationery Office.

Great Britain

(76.92)

The report highlighted variations in life expectancy associated with class or residency in statistics: middle-class people lived longer and healthier because they could afford to pay for sewage removal and fresh water connection to homes. The argument about the importance of sanitary conditions contributed to the passing of the Public Health Act and the Public Health Bill.

2

Engels F. The condition of the working class in England. Leipzig: Otto Wigand.

Great Britain

(55.18)

This book proposed that the industrial revolution made workers worse off: industrial workers had lower income, worse living environments and poorer health than their pre-industrial peers.

3

Durkheim, É. (1897). Le suicide.

France

(61.69)

This book studied suicide and its social causes: suicide was found to be associated with nationality, religion, age, sex, race, marital status, economic status, educational level, family size, place of residence, and exposure to war conflicts.

4

Du Bois WEB & Eaton I. The Philadelphia Negro: a social study (No. 14). Published for the University.

USA

(31.10)

This book presented the first statistical social study on a black community in the US: “Negro problem” was ostensibly “not one problem, but rather a plexus of social problems” caused by whites’ enforcement of racial discrimination and a provision of unequal opportunity.

5

Faris REL & Dunham HW. Mental disorders in urban areas: an ecological study of schizophrenia and other psychoses. Oxford, England: Univ. Chicago Press

USA

(20.73)

This book revealed a close relationship between mental disorders and the ecological structure of a city using ecological mapping: the distribution of schizophrenia was associated with sex, race, income, social relationship and home location.

6

World Health Organization (WHO). Constitution of the World Health Organization.

World Health Organization

(16.99)

The preamble of the WHO constitution defines health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” and proposes that “the enjoyment of the highest attainable standard of health is one of the fundamental rights of every human being without distinction of race, religion, political belief, economic or social condition”.

7

United Nations (UN) General Assembly. Universal declaration of human rights. UN General Assembly.

United Nations

(17.34)

The declaration sets health as a fundamental human right and proposes that “everyone has the right to a standard of living adequate for the health and well-being of himself and of his family”, and “motherhood and childhood are entitled to special care and assistance”.

8

Robinson WS. Ecological correlations and the behavior of individuals. American Sociological Review, 15.

USA

(12.05)

This study established ecological correlations (also spatial correlations) of behaviors of individuals: ecological correlations can measure the strength of a relationship and correlations at the group level can be much higher than those at the individual level.

9

Cronbach LJ. Coefficient alpha and the internal structure of tests. Psychometrika, 16(3), 297–334.

USA

(13.04)

This paper suggested the use of Cronbach’s alpha (or coefficient alpha) for measuring reliability (internal consistency) of psychometric instruments/scales, which has since been widely adopted in studies in psychology, social sciences, business, nursing, and other disciplines.

10

Talcott P. The social system. Routledge.

USA

(9.81)

This book presents a classic study on social systems and the “Theory of Action”, which laid a robust foundation for social systems theories and provided a theoretical framework for studies in a variety of areas, including medical practice, kinships and role-socialization, psychological relationships, and religious organization.

11

Festinger L. A theory of social comparison processes. Human relations, 7(2), 117–140.

USA

(11.36)

This book extends the previous proposed theory of social comparison to studies appraising and evaluating abilities and opinions: how individuals evaluate their own opinions and abilities by comparing themselves to others in order to reduce uncertainty and learn how to define self.

12

Allport GW, Clark K & Pettigrew T. The nature of prejudice.

USA

(9.76)

This book redefines intergroup relationships and prejudice: the Allport’s Scale was developed to measure prejudice ranging from ant locution to genocidal extermination.

13

Kaplan EL & Meier P. Nonparametric estimation from incomplete observations. Journal of the American statistical association, 53(282), 457–481.

USA

(8.57)

This study developed the Kaplan–Meier estimator, a nonparametric estimation method, for analyzing the survival function using incomplete lifetime data. It has fewer assumptions and is simpler compared with the parametric methods, which is particularly useful for data with a ranking but no clear numerical interpretations.

14

Hollingshead AB & Redlich FC. Social class and mental illness: Community study.

USA

(7.62)

This research monograph found a true link between social class and the distribution of mental illness being treated and the place of patients being treated in populations.

15

Goffman E. stigma. Notes on the Management of Spoiled Identity. New York: Simon and Shuster.

USA

(16.00)

This book discusses how social stigma (e.g. social deviation, physical or mental defects) is developed and denies full social acceptance of some groups and individuals.

16

Katz S. Studies of illness in the aged. The index of ADL: a standardized measure of biologic and psychologic function. JAMA, 185, 94–99.

USA

(8.71)

This study developed the ADL index measuring primary biological and psychosocial functions, and proposed the use of the ADL index as a tool for assessing the outcomes of clinical interventions which can guide clinical practices and help improve our understanding about aging.

17

Arrow KJ. Uncertainty and the Welfare Economics of Medical Care. The American Economic Review, 53(5):941–73.

USA

(8.19)

This paper summarized the special characteristics of the medical care market: differences between the medical care market and a typical competitive market. It highlighted the uncertainty and welfare economics of medical care.

18

Glaser BG, Strauss AL & Strutzel E. The discovery of grounded theory; strategies for qualitative research. Nursing research, 17(4), 364.

USA

(19.12)

This book describes the grounded theory, a new interpretive approach (compared with the positivism approach) to qualitative studies on emerging social and cultural issues. According to the grounded theory, new theories arise from qualitative data. This approach has since been widely endorsed by the international research community.

19

Antonovsky A. Social class, life expectancy and overall mortality. The Milbank Memorial Fund Quarterly, 45(2), 31–73.

Israel

(5.64)

This study revealed class influences on one’s chance of alive: the largest class difference existed in the middle years of life.

20

Kitagawa EM & Hauser PM. Differential mortality in the United States: A study in socioeconomic epidemiology.

USA

(6.62)

This book presents findings of a study that revealed differential mortality across a broad spectrum of social and economic factors (including age, sex, education, income, occupation, race, marital status, parity, nativity, and geographic classifications): lower socioeconomic status is associated with higher risks of dying and lower life expectancy.

21

Andersen R & Newman JF. Societal and individual determinants of medical care utilization in the United States. The Milbank Memorial Fund Quarterly. Health and Society, 95–124.

USA

(5.75)

This study provided a widely-accepted framework for operationalizing assessment of “equitable distribution of health services”: health care utilization is determined by both need factors and enabling factors at the individual, household and societal levels.

22

Berkman LF & Kawachi I. Social Epidemiology.

USA

(1.33)

This is the first book of social epidemiology, describing a new sub-discipline in the field of epidemiology that focuses particularly on the effects of social class on health.

23

Office of Disease Prevention and Health Promotion, US Department of Health and Human Services: Healthy People 2010. http://www.health/gov/healthypeople/.

USA

(1.16)

This US governmental document depicts two overarching goals: to enhance life expectancy and the quality of life and to eliminate health disparities between different segments of the population. It contributed to the development of various models measuring disparities.

24

Smedley BD, Stith AY & Nelson AR. Unequal treatment: Confronting racial and ethnic disparities in health care.

USA

(1.69)

This Institute of Medicine report warned that racial and ethnic minorities received lower quality healthcare than whites, and the bias, prejudice and stereotyping of healthcare providers might have contributed to the unequal treatment. A comprehensive multi-level strategy was proposed to eliminate these disparities.

25

Marmot M. Social determinants of health inequalities. The lancet, 365(9464), 1099–1104.

UKWHO

(0.40)

This paper describes the tasks of the WHO Commission on Social Determinants of Health, addressing social factors leading to ill health and health inequity. It not only reviewed the existing body of knowledge but also raised societal debates on health inequalities within and between countries.

26

Galobardes B, Shaw M, Lawlor DA, Lynch JW & Smith GD. Indicators of socioeconomic position (part 1). Journal of Epidemiology & Community Health, 60(1), 7–12.

UKUSA

(0.39)

This study presents a comprehensive list of indicators measuring socioeconomic position (SEP) that were commonly used in health research (education, income, housing characteristics, occupation, occupational based measures, proxy indicators, composite indicators, and area level measures): the theoretical basis, measurement, interpretation, strengths and limitations of each indicator.

27

Wilkinson RG & Pickett KE. Income inequality and population health: a review and explanation of the evidence. Social science & medicine, 62(7), 1768–1784.

UK

(0.32)

This paper reviewed the relationship between income inequality and inequality in population health, and proposed that income distribution is a convenient and widely applicable measure for socioeconomic stratifications.

28

Van Doorslaer E, Masseria C, & Koolman X. Inequalities in access to medical care by income in developed countries. Canadian medical association journal, 174(2), 177–183.

Netherlands,UK, OECD countries

(0.22)

This study examined inequity in the use of physician services (in 2000) in the 21 OECD countries using data extracted from the national household surveys. The study found that primary care (general practice) was pro-poor or distributed fairly equally, while specialist care tended to be pro-rich.

29

Marmot M, Friel S, Bell R, Houweling TA, Taylor S & Commission on Social Determinants of Health. Closing the gap in a generation: health equity through action on the social determinants of health. The Lancet, 372(9650), 1661–1669.

UK, WHO

(1.25)

This paper summarized findings of the WHO Commission on Social Determinants of Health, and called for all governments to lead actions addressing social determinants of health with an aim to achieve health equity. The paper also set key action areas associated with daily living conditions and their underlying structural drivers.

30

Mackenbach JP, Stirbu I, Roskam AJR, Schaap MM, Menvielle G, Leinsalu M & Kunst AE. Socioeconomic inequalities in health in 22 European countries. New England Journal of Medicine, 358(23), 2468–2481.

Netherlands, Sweden, Estonia, European Union countries

(0.58)

This study compared the magnitude of inequalities in mortality and self-assessed health among the 22 European countries using a regression-based inequality index: inequalities in health varied across the European countries, which were associated with the socioeconomic status of each country.

31

O’donnell O, Van Doorslaer E, Wagstaff W & Lindelow M. Analyzing health equity using household survey data.

Netherlands,World Bank

(0.34)

This book provides researchers with a step-by-step practical guide to the measurement of various aspects of health equity: in access to health services, in financial contributions to health systems, and in health outcomes. This led to a more comprehensive approach to monitoring of the trends in health equity, understanding of the causes of health inequities, extensive evaluation of the effects of development programs on health equity, and development of effective policies and programs to reduce inequities in the health sector.