rome, 16 may 2008 a life course perspective on social inequalities in health david blane with juliet...
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Rome, 16 May 2008
A Life Course Perspective on Social Inequalities in Health
David Blane
with Juliet Stone, Gopalakrishnan Netuveli
Imperial College London
ESRC International Centre for Life Course Studies in Society & Health
Rome, 16 May 2008
Contents
Origins
Theory
Methods
Social inequalities in health
Limits of the life course approach
Summary
Rome, 16 May 2008
Origins
The life course now is a core theme in social epidemiology.
1990s
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Biological programming
Organ development in utero (as indexed by eg. birth weight) and during infancy determines maximum function during adulthood*
Examples
Lung development – adult COPD
Kidney development – adult hypertension
Pancreatic development – adult diabetes
Origins
*Barker D 1991, 1994 (BMJ Books).
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Birth cohort studies
1946 birth cohort at age 36 years
first use of accumulation*
risk of lower respiratory tract disease & reduced lung function at 36 accumulates with chest infections and poor, crowded housing during early childhood, air pollution exposure during later childhood and tobacco smoking during early adulthood
Origins
*Mann et al. 1992 J Epidemiol Com Health
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Health inequalities
Behavioural risk factors account for only c.1/3 of class difference in mortality risk.*
Mortality risk is fine grained.**
Social structure = disadvantages (or advantages) cluster
cross-sectionally and accumulate longitudinally.***
Origins
* Rose & Marmot 1981 Brit Heart J
** Goldblatt 1990 HMSO*** Blane 1995 American J Public Health
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Theory: Models of the life course
Critical periods
Accumulation
Pathways
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Model: Critical periods
Extends the idea of biological programming to include
Childhood Psycho-social stress at the time of brain maturation may both inhibit child growth and mis-set the developing BP control mechanisms, producing later high BP*
Social development Key social transitions**
* Montgomery et al. 2000 Archives Disease Childhood
** Bartley et al. 1997 British Medical Journal
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Model: Accumulation
Disadvantages, or advantages, tend to cluster cross-sectionally
occupation + residence + area of residence + consumption
and accumulate longitudinally. childhood + adulthood + older ages
This social process may have a major impact on health through the accumulation of numerous relatively minor effects.*
* Blane et al. 1997 European J Public Health
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Model: Pathways
Early advantage or disadvantage sets a person on a pathway to a later exposure that is the aetiologically important event.*Educationally successful women (pathway) tend to delay their first
pregnancy (aetiologically important event), which increases their risk of breast cancer.
* Power & Hertzman. 1997 British Medical Bulletin
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Models: A judgement
Models are difficult to distinguish empirically* and conceptually**
Perhaps best to see accumulation as the general social process which drives life course trajectories; with critical periods and pathways, in addition to accumulation, being the biological processes of disease causation**
* Hallqvist et al.2004 Social Science and Medicine** Blane et al. 2007 Revue d’Epidemiologie et de Sante Publique
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Methods
Birth cohort studies
Linked-register data sets
Epidemiological archaeology
historical study +
tracing to present-day location +
retrospective data +/-
Lifegrid (event history calendar)
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Birth cohort studies
1946 birth cohort
Health at 36 years* and physical disability and handicap at 43** influenced by parental social class, health during
childhood and own adult social class Poor diet*** and obesity**** at 36 years influenced by manual parental social class and few educational qualifications
Methods
* Kuh & Wadsworth 1993 Soc Sci Med
** Kuh et al. 1994 J Epid Com Health*** Braddon et al. 1988 J Epid Com Hlth**** Braddon et al. 1986 Brit Med J
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Linked registers
Birth weight and blood pressure at age 50 years in 1300 Swedish men*
weak inverse linear relationship, only for systolic pressure
Birth weight during 1915-29 and all deaths among 14600 Swedish men & women to 1995**
weak inverse relationship for cardiovascular disease deaths, only
for men
Methods
* Leon et al. 1996 British Medical J
** Leon et al. 1998 British Medical J
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Boyd Orr lifegrid sub-sample
Height measured during childhood in 1937-39
Height and blood pressure measured during early old age in 1997-98
Child growth (child height conditioned on adult height) predicted pulse pressure and systolic blood pressure 60 years later.*
Epidemiological archaeology
* Montgomery et al. 2000 Arch Dis Child
Methods
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Health inequalities and life course
Predictive power
Aetiological insights
Health inequality debates
Social policy implications
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Predictive power
West of Scotland Collaborative Study
Life course socioeconomic position (child, first job and adult manual social class, range 0-3) predicted systolic and diastolic blood pressures, serum cholesterol concentration, height, body mass index, lung function (FEV1), symptoms of angina and chronic bronchitis and
21-year mortality risk.
Inequalities
* Davey Smith et al. 1998 Brit Med J
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Aetiological insights
West of Scotland Collaborative Study*
cause-specific mortality and mutually adjusted child & adult social class
Lung cancer mostly adult class
Coronary heart disease and respiratory disease accumulating child and adult class
Stroke and stomach cancer mostly child class
Inequalities
* Davey Smith et al. 1998 Brit Med J
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Unresolved debates
General susceptibility* Mortality risk determined by balance of advantage and disadvantage
Cause of death determined by specifics of an individual’s social trajectory
Gradient constraint** Health-related social mobility constrains, rather than creates,
widening inequalities
Inequalities
* Blane et al. 1997 European J Pub Health** Bartley & Plewis 1997 J Hlth Social Beh
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Social policy implications
• Traditional welfare state safety nets assume that misfortune soon will be replaced by the person’s normal, more advantaged, state.
• The accumulation model draws attention to the likelihood that misfortune will have been preceded by earlier disadvantages, requiring a springboard to repair previous damage.*
* Bartley et al. 1997 British Medical J
Inequalities
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Limits of the life course approach.
Spectrum of impact.
Major social disruption.
Effect diluted at older ages? (speculative)
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Spectrum of impact
Physiological risk factors influenced by whole life course; behavioural risk factors influenced mainly by current context*
Modest life course influences on diet at older ages**
Quality of life at older ages influenced mainly by current circumstances***
Limits
* Blane et al. 1996 British Medical J** Maynard et al. 2006 Eur J Pub Hlth*** Wiggins et al. 2004 Ageing & Society
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Major social disruption
Many areas of health where life course perspective adds little
Not an alternative to a concern with the cross-sectional and immediate
Acute shortening of life expectancy that followed end of USSR in 1989 (life course might help explain particular vulnerability of single men)*
Limits
* Watson 1995 Social Science and Medicine
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Dilution at older ages?
Norwegian linked registers
• 19,000 people aged 70 years in 1990, traced back to 1960 and forward to all deaths during 1990-1998
• Social gradient in mortality explained mostly by social position in 1990, with minor cumulative effects 1960-1980*
• Is life course effect weakened at older ages?
Limits
* Naess et al. 2006 Social Science & Med
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Summary
Life course approach not relevant to all aspects of health inequalities. Most relevant to inequality in chronic disease morbidity and mortality. Accumulation is main social process and one of the three aetiological processes.
Rome, 16 May 2008
Follow-up contact
E-mail: [email protected]
Website of ESRC International Centre for Life Course Studies in Society and Health: www.ucl.ac.uk/icls.