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Bruna Galobardes Department of Social Medicine University of Bristol, UK

The association between early life socioeconomic position and adult health, from mortality to preclinical disease. What do we know?. Bruna Galobardes Department of Social Medicine University of Bristol, UK National Poverty Center, March 2009. What is a life course approach?.

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Bruna Galobardes Department of Social Medicine University of Bristol, UK

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  1. The association between early life socioeconomic position and adult health, from mortality to preclinical disease. What do we know? Bruna Galobardes Department of Social Medicine University of Bristol, UK National Poverty Center, March 2009

  2. What is a life course approach? A life course approach in epidemiology investigates the long term effects on health and chronic disease risk of physical and social hazards during gestation, childhood, adolescence, young adulthood and later adult life (and across generations). It studies the biological, behavioural and social pathways that operate across the life course and influence the development of chronic diseases.

  3. “It is insufficient to glibly state that all health and social outcomes are due to life course influences. This is analogous to stating that all health is a function of genetic and environmental exposures. Whilst factually correct it does not further our understanding of aetiology or help policy formulation.” Ben-Shlomo & Kuh (Lifecourse approach to chronic disease epidemiology, 2nd edition)

  4. Life course epidemiology – stating the obvious? “The ringing in your ears – I think I can help!”

  5. Early life socioeconomic position (SEP) and cause-specific mortality: is the association established?

  6. The importance of looking at specific causes of death:helps establishing causal associations and describing the pathways that link early socioeconomic circumstances with later disease.

  7. Evidence from : Systematic review of individual-level studies Ecological studiesMigration and place of birth studiesLong-term disease trends

  8. Evidence from individual-level studies: Bruna Galobardes, George Davey Smith and John W. LynchEpidemiologic Reviews 2004;26:7-21J Epidemiol Community Health 2008;62:387-90Ann Epidemiol 2006;16:91-104 The systematic reviews on mortality are based on at least 125,961 deaths (66 558 deaths in a Swedish study and 20 887 deaths in a study from Norway) from 40 studies (some reported in more than one publication): 38 prospective, 2 case-control, 1 cross-sectional.

  9. Inclusion criteria: individual-level studies, adult mortality (studies reporting grouped fatal and non-fatal events were excluded or inclusion of hypertension in the outcome definition)Countries: United Kingdom, Sweden, Finland, Norway, Denmark, Netherlands, United States, Russia, France, Belgium and South Korea. Birth cohorts: The majority included people born during or before the 1940s and 1950s, and the youngest birth cohorts dated from the late-1950s to the 1960s.In the initial review 19 of the 29 studies measured the participants’ SEP during childhood or young adulthood. The remainder obtained data by participant recall during adulthood.The father’s occupation was the most common indicator.

  10. Main conclusions: Most studies support an association between childhood socioeconomic position and overall mortality. Not all causes of death are equally related to childhood socioeconomic conditions.

  11. Main conclusions: • • Childhood SEP is particularly important for mortality from stomach cancer. • Childhood SEP was particularly important for haemorrhagic stroke but there was not consistency across studies. • • Childhood circumstances contribute, together with socioeconomic conditions in adult life, in determining mortality from coronary heart disease, liver and lung cancer, respiratory-related deaths and diabetes. The relative contribution of child-versus-adult circumstances varied in different contexts. • • Childhood circumstances may contribute to external (including unintentional injuries and homicide) and alcohol-related causes of death, especially in northern European countries. • • There is no evidence for an association with overall non-smoking-related cancers.

  12. Stomach cancer mortality

  13. Davey Smith, Hart, Blane et al. BMJ 1998;316;1631-1635

  14. Infant mortality in 1921-3 and stomach cancer rates in 1991-3 for men aged 65-74 Leon & Davey Smith BMJ 2000;320:1705-6

  15. Migration studies: Risk of stomach cancer in first and second generation migrants in Sweden Hemminki & Li Int J Cancer 2002;99:229-37    Bold type: 95% CI does not include 1.00.

  16. Stroke mortality

  17. Lawlor et al. Lancet 2002;360:1818-23

  18. Evidence from disease trends … Lawlor et al. Lancet 2002;360:1818-23

  19. Evidence from disease trends … Lawlor et al. Lancet 2002;360:1818-23

  20. Evidence from individual level studies … Childhood social class and stroke subtype: Manual vs. Manual vs.+ non-manual non-manual Haemorrhagic 2.84 (1.12-7.20) 3.22 (1.15-9.03) Ischaemic 1.25 (0.77-2.03) 0.92 (0.53-1.61) +risk factor adjusted Hart and Davey Smith; J Epidemiol Community Health 2003

  21. Evidence from individual level studies … Hart et al. JECH 2003;57:385-91

  22. “studies from Sweden and Norway, and the mothers of the 1958 cohort found both types of stroke, ischemic and hemorrhagic, had a similar social patterning thus not supporting earlier reports where worse childhood SEP was a stronger predictor for hemorrhagic stroke “ Galobardes, Davey Smith, Lynch. J Epidemiol Community Health 2008;62:387-90

  23. Cardiovascular disease mortality and morbidity

  24. Those who experienced worse socioeconomic conditions in their childhood, independently of their circumstances during adult life, generally were at greater risk for developing and dying of CVD: Davey Smith, Hart, Blane et al. BMJ 1998;316;1631-1635

  25. Sinhg-Manoux, Ferrie, Chandola et al. Int J Epidemiol 2004;33:1072-1079

  26. The relative contribution of child-versus-adult socioeconomic conditions varied in different contexts: Smoking: Different life course exposure to tobacco smoking may explain the relative different contributions of child versus adult SEP on CHD in different countries. In US: Childhood SEP more important. Alameda County study in the United States, those from poorer backgrounds during childhood were less likely to quit and therefore had smoked more throughout their lives, despite the socioeconomic reversals in smoking pattern in the adult population. Netherlands: Conversely, a cross-sectional study of a younger population showed that smoking was influenced more by adult SEP.

  27. • Pre-clinical CVD – atherosclerosis: At the time of publication of the systematic review there were 2 studies measuring carotid intima media thickness (a measure of the width of the artery wall) or carotid stenosis. Both studies reported higher levels of atherosclerosis among women but not among men. More recent studies (“not systematic”) : Multi-Ethnic Study of Atherosclerosis (MESA): Childhood SEP was independently associated with subclinical IMT in both men and women. Young Finns study, parental occupation in childhood or young adulthood of the participant was not associated with IMT or flow mediated vasodilation. Atherosclerosis Risk in Communities Study (ARIC, US): “Lower cumulative life course SEP was associated with higher burden of subclinical atherosclerosis”

  28. Issues to consider: Confounding by adult SEP Does the association persist among younger cohorts? Effects across generations

  29. Confounding by adult SEP Glasgow Alumni Cohort study: >90% class I and II in adulthood Galobardes et al. JECH 2006;60:527-9

  30. Does the association persist among younger cohorts? 1 Swedish cohort (Lawlor et al, 2007); 2 Norwegian cohort (Naess et al, in press; 3 Collaborative study (Davey Smith et al. 1998) • Younger birth cohorts have not experienced the level of socioeconomic strain previous birth cohorts had, however, the association between childhood SEP and mortality can still be found

  31. Effects across generations: Osler et al. JECH 2005;59:38-41

  32. Effects across generations: Osler et al. JECH 2005;59:38-41

  33. Models / pathways can explain life course inequalities in health: Cumulative vs. interaction Importance of education Genetic/in-utero vs. environment

  34. Theoretical life course models • Critical period model • with or with out later effect modifier • with later life effect modifier • Accumulation of risk • with independent and uncorrelated insults • with correlated insults • “risk clustering” • “chains of risk” with additive or trigger pathways Ben-Shlomo & Kuh IJE 2002

  35. Critical and sensitive periods • Critical period – a time period only during which an exposure has an effect. • Thalidomide and limb abnormalities • Imprinting of parental characteristics (Lorenz) • Sensitive period - a time period during which an exposure has a greater effect than outside this period • Learning a second language in childhood • Clinical disease associated with infectious disease exposure

  36. Theoretical life course models • Critical period model • with or with out later effect modifier • with later life effect modifier • Accumulation of risk • with independent and uncorrelated insults • with correlated insults • “risk clustering” • “chains of risk” with additive or trigger pathways Ben-Shlomo & Kuh IJE 2002

  37. TIME Accumulation model – independent risks O U T C O M E M E A S U R E A B C Kuh et al (JECH 2003:57:778-783)

  38. TIME Accumulation model – risk clustering O U T C O M E M E A S U R E D A B C Kuh et al (JECH 2003:57:778-783)

  39. TIME Chains of risk model – trigger O U T C O M E M E A S U R E A B C Kuh et al (JECH 2003:57:778-783)

  40. TIME Chains of risk model – additive O U T C O M E M E A S U R E A B C Kuh et al (JECH 2003:57:778-783)

  41. Cumulative Social Class All 3 non-manual 2 non-manual 2 manual All 3 manual P value for trend All cause Age adjusted 1 1.29 (1.08, 1.56) 1.45 (1.21, 1.73) 1.71 (1.46, 2.01) < 0.0001 Age & risk factor 1 1.30 (1.08, 1.57) 1.33 (1.11, 1.60) 1.57 (1.33, 1.85) < 0.0001 CVD Age adjusted 1 1.51 (1.16, 1.98) 1.90 (1.47, 2.45) 1.94 (1.53, 2.45) < 0.0001 Age & risk factor 1 1.57 (1.20, 2.05) 1.78 (1.37, 2.31) 1.92 (1.51, 2.45) < 0.0001 Relative death rates (95% CI) by cumulative social class, adjusted for age and risk factors, for men in West of Scotland Collaborative Study (Davey Smith et al 1997)

  42. Importance of education Lawlor et al AJE 2006;164:907-15

  43. Genetic/in-utero vs. environment * ** * 1.69, ** 1.76 Osler et al. IJE 2006;35:1272-77

  44. Explanations for these findings … Genetic/in-utero vs. environment

  45. Underlying genetic mechanism • Genetic factor poor health low SEP • Inherited personality traits SEP • health-related behaviours • IQ • Prenatal programming effect the mother’s lifestyle and health during pregnancy child’s foetal development • Assortative mating: father/partner will have similar SEP and health Genetic/in-utero vs. environment

  46. Chance finding Selection bias Genetic/in-utero vs. environment Osler et al. IJE 2006;35:1272-77

  47. Barker & Osmond BMJ 2000;293:1271-75.

  48. Mortality rates per 10,000 person years 1990-94 by indices of housing conditions in 1960 and household income in 1990, Oslo From: Claussen et al. J Epidemiol Community Health 2003;57:40-45.

  49. All cause mortality by cumulative social class and car driving Davey Smith et al, BMJ 1997

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