Contact:
Dr. David Blane
Division of Neuroscience,
Imperial College of Science,
Technology & Medicine
St Dunstan's Road
London W6 8RP
Tel: +44 (0)208 8467383
Fax: +44 (0)208 8461329
Click to email

Principal Researchers:
Dr. David Blane
Professor George Davey Smith
Mr. Lee Berney
Ms. Paula Holland

Duration of Research:
October 1997 - September 1999

Background
The fact that there are persisting and widening inequalities in health is well known. What is less well understood is why. Recent evidence has pointed to the importance of explanations that look at how an individual's health is shaped by experiences across the life course, from birth to old age. In this life course perspective, the poorer health of those in lower socio-economic groups is seen to reflect the cumulative effect of exposure to health-damaging environments across their life course.

Life course influences are recognised to be important because major diseases of adulthood, including coronary heart disease (CHD) and many cancers, have long natural histories which may stretch back to foetal life and infancy. Many of the risk factors associated with these diseases, like diet, tobacco smoke, atmospheric pollution and occupational dust, need long exposures. As a result, the risks of dying prematurely from diseases like CHD and chronic respiratory disease vary with the proportion of one's life spent in disadvantaged social circumstances.

Aims and Objectives
The aims of this study are:

• to investigate life course influences on health;
• to establish the contribution made to socio-economic variations in health in old age by three clusters of factors: health and social circumstances in childhood, exposure to hazards during adulthood and current living conditions.

Study Design
Life course information will be collected from historical records and retrospective interviews with 300 people aged between 65 and 75 years. The respondents all took part in a survey of child health and social conditions, conducted by Sir John Boyd Orr in 1937-39. A stratified random sample of surviving members of the 1937-39 survey have been traced to their current locations. They will be interviewed using a lifegrid method which collects reliable information on past experiences and events.

For every respondent, information will be available on their health and social circumstances during childhood (from the records of the 1937-39 survey), the length of exposure to any of a range of hazards during adulthood (from the lifegrid interview) and their health and social circumstances during early old age (also from the interview). Analysis of these data will identify the precursors of individual and social variations in health in early old age.

Policy Implications
An increasing proportion of the British population is above retirement age. The results of the study will be relevant to policy because early old age is the time of life when serious diseases become frequent and much use is made of health services. Health in early old age is also an important influence on the quality of life in these age groups and on whether life after retirement offers the possibility of a fulfilling 'Third Age'. The study's results will also help current attempts to identify interventions to reduce social variations in health, by suggesting where in the life course they would be most effectively directed.

Project Summary
It is increasingly recognised that differential exposure to disadvantage across the lifecourse is an important determinant of health inequalities. However, research to date has shed only a partial light on the processes by which biological, social and material risks combine to influence health. Most of this research focuses on the working-age (and male) population. Much less is known about the lifecourse influences on the health of men and women over retirement age.

Along with the project led by Emily Grundy, the project focused on health inequalities in early old age. It investigated the contribution of childhood circumstances, adult experiences and current circumstances to variations in health in 65-75 year olds. The study members had been participants in Sir John Boyd Orr's survey of child health and development conducted between 1937 and 1939, and were aged between 5 and 17 at clinical examination. The study participants were traced and nearly 300 were interviewed in 1997-8. A specially-designed method, the lifegrid method, was used to collect retrospective data on their lifetime exposures. Anthropometric measures, and measures of lung function and blood pressure, were also taken.

Key findings

• Socio-economic inequalities in health were evident in early old age. Statistically significant differences were found for lung function (males and females), height (females), leg length (females) and Body Mass Index (females).
• Advantage and disadvantage accumulated across the whole lifecourse. Disadvantage during childhood predicted forward to future accumulating disadvantage in the rest of life; disadvantage after retirement was preceded by disadvantage during the earlier stages of life.
• The length of exposure to health-damaging environments was related to health and social circumstances in childhood. Child height, measured in 1937-39 and standardised for age at examination and for gender, was related in a graded fashion to subsequent lifetime hazard exposures (and height in this context can probably be interpreted as an indicator of childhood growth).
• The strength of the relationship between childhood growth (measured by child height) and subsequent hazard exposure varied with childhood social class. Children from non-manual homes were protected from subsequent hazard exposure if they were growing slowly or in poor health. In other words, health and social disadvantage during childhood interacted to predict the levels of disadvantage which were encountered during subsequent life.
• Lifecourse factors related in different ways to different dimensions of health in early old age. For example, the influences on lung function accumulated across the whole lifecourse, and involved factors in childhood, adulthood and early old age while the influences on height were fixed primarily in early life. The influences on blood pressure point to a conditional process, in the sense that factors from different stages of life were required sequentially before the later life effect was produced. In general, lifecourse effects were more apparent for objective measure of health, like lung function and blood pressure, than for self-reported measures.
• The project also contributed to the methodology of health inequalities research by enhancing the lifegrid technique for the retrospective collection of lifecourse information. The lifegrid method, developed by David Blane, collects information by intensive interview, using a lifegrid and indicators of exposure to environmental hazards which have been shown to be accessible to long-term recall. In a further refinement of the method, lifegrid data collected in interviews at age 65-75 years were linked to archived information from the Boyd Orr study.