Determinants of health and disease

1. Determinants of health and disease Cesar Victora Universidade Federal de Pelotas Washington, June 2002

2. Structure of presentation • Populations and individuals • Approaches to understanding determinants of health and disease • Life-course approaches • Challenges for the future

3. Determinants of health and disease Models of disease causation

4. Sick individuals and sick populations G. Rose, 1985

5. Determinants of individual cases measured through relative risk depend on heterogeneity of exposure may miss most important causes if highly prevalent Determinants of population incidence rates identified through ecologic comparisons of exposure and disease distributions Sick individuals and sick populationsG. Rose, 1985

6. Mosley-Chen analysis Mosley and Chen, 1983

7. Social sciences approach emphasis on distal determinants political and ideological structure socioeconomic status behavioral factors Biological sciences approach emphasis on proximate determinants water/sanitation environment immunity genetic factors etc Traditional approaches to understanding determination of health status Mosley and Chen, 1983

8. Unicausality one germ, one disease around 1900 Agent/ host/ environment interaction 1930’s-1940’s the agent alone has limited explanatory power Multicausality 1960’s each disease may have several different causes “web of causation” Genomic era 1990’s renewed emphasis on individual susceptibility Biological sciences approaches

9. Emphasis on individuals No hierarchy among causes No discussion of the causes of causes Emphasis on finding technological solutions (“magic bullets”) Effective for controlling many diseases vaccine preventable diseases micronutrient deficiencies etc Biological sciences approaches

10. Mosley-Chen model for child health Mosley and Chen, 1983

11. McMahon et al, 1960: Epidemiologic Methods • Introduced concept of “web of causation” • Advice: • abandon semantic exercises aimed at hierarchic classification of causes • seek the necessary causes most amenable to practical intervention and nearest to the specified outcome

12. Epidemiology and the web of causation: has anyone seen the spider? • Models do not exist independent of theories • The underlying model of the causal web is biomedical individualism • the logical solutions are biomedical interventions at individual level • Web approach • gives equal weight to factors that are hierarchically different • does not differentiate between determinants at individual and population level Source: Krieger N, 1994

13. Health Inequality Research in Latin America and Caribbean Almeida, Kawachi, Pellegrini, Dachs (in press)

14. Health Inequality Research in Latin American Countries Almeida, Kawachi, Pellegrini, Dachs (in press)

15. Scandinavian countries Gini’s index =0.25 World’s 10 most unequal countries Gini’s index for income concentration UNDP 2001

16. Emphasis on population level determinants Structural factors (economic, political and social) are the main determinants of health status social class Mixed reliance on empirical and quantitative approaches Latin American scientific production is almost “invisible” in North America and Europe (Breilh, 1995) The Latin American Social Epidemiology Movement

17. AInequity continues to be the leading health problem in the Americas” Pan-American Health Organization (1998). Leading Pan-American Health. Washington: PAHO (Official Document no. 287).

18. Determinants of health and disease A model for child health

19. ADVOCACY POLITICAL ACTION Distal/socioeconomic Income Land Tenure Parental Education Employment, etc Intermediate/environmental Intermediate/behavioral Water, sanitation Housing Indoor pollution Crowding Food availability COMMUNITY-LEVEL INTERVENTIONS Risk behaviors Preventive behaviors Careseeking Home management of disease SERVICES DELIVERY Proximate/biological Nutritional status Disease incidenceDisease severity Child health/disease Economic structure Political and ideological superstructure Macroenvironment Government policies and actions Non-health-sector interventions Health-sector interventions preventive curative Global power relations International trade and investments Globalization GENETIC FACTORS

20. Infant mortality in selected Latin American countries, 1960-94 Source: Dachs N, PAHO

21. IMR and land tenure:advocacy

22. Two hierarchies

23. 1. Unit of aggregation Global National State/provincial Community Household Family Individual

24. The different levels of inequities • “An association between socioeconomic deprivation and ill-health has been found wherever and whenever it has been looked for”(Sir Douglas Black, 2001) • “and at whatever level of aggregation it has been investigated”

25. Distal/socioeconomic Income Land Tenure Parental Education Employment, etc Intermediate/environmental Intermediate/behavioral Water, sanitation Housing Indoor pollution Crowding Food availability Risk behaviors Preventive behaviors Careseeking Home management of disease Proximate/biological Nutritional status Disease incidenceDisease severity Child health/disease 2. Level of determination Individual

26. In summary • Studies of determinants of health must address different levels of aggregation • populations • sub-populations • individuals • Hierarchies between levels and among determinants are important • Multiple disciplines are required for a thorough understanding of health determinants • Actions to improve health must address different levels of determination

27. Determinants of health and disease The life-course approach

28. The 1982 Pelotas Birth Cohort Study • Population-based cohort of 6,000 children • Follow up from birth to 19 years • Probably longest and largest birth cohort from a developing country

29. 1982 Birth Cohort 1982 2000

30. Field work in Pelotas, 1980’s

31. Cohort visits

32. Lack of antenatal care, 1982

33. Infant mortality, 1982

34. Stunting prevalence at 20 months, 1984

35. Summary of early findings on socioeconomic inequities, 1982-86 • Children from low income families had the worst health indicators, except for • caesarean sections • overweight

36. Achieved schooling by year 2000 (boys) P<0.001

37. Risk factors for chronic diseases in 2000 (boys) MONTHLY INCOME (US$) All P<0.01, except * (0.1>P>0.05)

38. Teenage pregnancies

39. Teenage pregnancies by 2000 according to family income (1982) n=443 P<0.001

40. Mean birthweight of children of adolescents, according to mother’s birthweight, 1982 3259 g n=406 P<0.001 2922 g

41. Low birthweight in two generations by income in 1982

42. The catch-up dilemma

43. Hospital admissions (1985) according to growth in 1982-84 (0-20 months) P<=0.03 Victora, Barros et al (IJE 2001)

44. Mortality from 20-59 months according to growth in 1982-84 (0-20 months) Based on 10 deaths, P=0.045 Victora, Barros et al (IJE 2001)

45. Obesity and overweight in 18-year-old boys according to growth from 0-20 months P<0.001 Victora, Barros et al (IJE 2001)

46. Asthma: the Hygiene Hypothesis

47. Asthma prevalence in 18-year-old boys by income in 1982 P=0.01 Lima, Victora et al (in press)

48. Risk factors in childhood reduce asthma in adolescence Analyses adjusted for socioeconomic confounders; all P<0.05 Lima, Victora et al (IJE 2001)

49. Summary of life-course results from Pelotas • Inequities by late adolescence are complex due to the nutrition and epidemiologic transitions • Risk factors in pregnancy and childbirth tend to repeat themselves in subsequent generations • Risk factors for infectious diseases in early life may protect against chronic diseases later on

50. Conclusions