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

Rome, 16 May 2008 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).

Rome, 16 May 2008 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 J Epidemiol Com Health

Rome, 16 May 2008 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

Rome, 16 May 2008 Theory: Models of the life course Critical periods Accumulation Pathways

Rome, 16 May 2008 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 Archives Disease Childhood ** Bartley et al British Medical Journal

Rome, 16 May 2008 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 European J Public Health

Rome, 16 May 2008 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 British Medical Bulletin

Rome, 16 May 2008 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 Revue d’Epidemiologie et de Sante Publique

Rome, 16 May 2008 Methods Birth cohort studies Linked-register data sets Epidemiological archaeology historical study + tracing to present-day location + retrospective data +/- Lifegrid (event history calendar)

Rome, 16 May 2008 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 J Epid Com Health *** Braddon et al J Epid Com Hlth **** Braddon et al Brit Med J

Rome, 16 May 2008 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 and all deaths among Swedish men & women to 1995** weak inverse relationship for cardiovascular disease deaths, only for men Methods * Leon et al British Medical J ** Leon et al British Medical J

Rome, 16 May 2008 Boyd Orr lifegrid sub-sample Height measured during childhood in Height and blood pressure measured during early old age in Child growth (child height conditioned on adult height) predicted pulse pressure and systolic blood pressure 60 years later.* Epidemiological archaeology * Montgomery et al Arch Dis Child Methods

Rome, 16 May 2008 Health inequalities and life course Predictive power Aetiological insights Health inequality debates Social policy implications

Rome, 16 May 2008 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 (FEV 1 ), symptoms of angina and chronic bronchitis and 21-year mortality risk. Inequalities * Davey Smith et al Brit Med J

Rome, 16 May 2008 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 Brit Med J

Rome, 16 May 2008 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 European J Pub Health ** Bartley & Plewis 1997 J Hlth Social Beh

Rome, 16 May 2008 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 British Medical J Inequalities

Rome, 16 May 2008 Limits of the life course approach. Spectrum of impact. Major social disruption. Effect diluted at older ages? (speculative)

Rome, 16 May 2008 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 British Medical J ** Maynard et al Eur J Pub Hlth *** Wiggins et al Ageing & Society

Rome, 16 May 2008 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

Rome, 16 May 2008 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 Social gradient in mortality explained mostly by social position in 1990, with minor cumulative effects * Is life course effect weakened at older ages? Limits * Naess et al Social Science & Med

Rome, 16 May 2008 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.

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