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Issue 3, January 1999, pp.8-9.

The lifegrid method in health inequalities research
Paula Holland, Lee Berney, David Blane and George Davey Smith

The importance of the lifecourse perspective
Explanations of why there are persisting socio-economic inequalities in health have drawn attention to the importance of socio-economic differences in people's living and working environments and in their health-related behaviour. Recent research has highlighted how exposure to disadvantaged environments and to health-damaging behaviours accumulate over the lifecourse, from before birth, through childhood and across adulthood. Lifecourse influences are increasingly seen to hold the key to understanding the existence and persistence of socio-economic inequalities in adult morbidity and mortality.(l)

While research is highlighting how disadvantage has cumulative effects on health, few studies have examined the extent of social inequalities in health amongst older people. This is despite the fact that older people experience the highest rates of morbidity and make the greatest use of health services (see Figure 1).

Figure 1: percentage of people i) reporting a limiting longstanding illness, ii) consulting an NHS GP in the 14 days before interview, by age: Great Britain, 1996

Source: ONS (1998) Living in Britain: Results from the 1996 General Household Survey, London: The Stationery Office, Tables 8.1 and 8.19

Our study, 'Social Variations in Health in Early Old Age', attempts to address this gap in health inequalities research. It examines the association between cumulative exposure to health-damaging residential and occupational environments through the lifecourse and socio-economic variations in physical health of men and women in early old age. By early old age, the impact of a lifetime's exposure to health insults is evident with chronic diseases becoming manifest. We have collected information on lifetime influences on health using the lifegrid method. Because the method provides an important new approach to studying health inequalities, this article describes what it is and what it can contribute to the understanding of health inequalities.

Alternative ways of collecting lifecourse information
One method of investigating lifecourse influences on health inequalities is to use prospective data, such as that from the birth cohort studies, designed to survey groups of individuals periodically from birth onwards. However, while cohort studies provide invaluable data they have limitations. Besides being expensive and subject to sample drop-out, introducing new questions or measures is problematic, and none of the British birth cohorts are yet old enough to examine health variations amongst older people. An alternative is to use retrospective methods, where study members are asked about events that happened previously in their lives. These methods are often criticised as being unreliable and subject to recall bias. In response to this criticism, the lifegrid interview method has been developed to gather lifecourse information retrospectively and improve accuracy of recall.

The lifegrid interview method
The lifegrid interview starts with interviewees providing a brief summary of major life events such as leaving school, marriage, birth of children, death of parents, moving residences and changing jobs. These events are recorded on a series of time-lines - such as family, residential and occupational - from birth to the present day. Figure 2 gives an example of a segment of a completed lifegrid for a woman born in 1935. The completed lifegrid allows the interviewer to structure the more detailed part of the interview that follows, focusing on specific areas of interest, such as housing and working conditions through the lifecourse. The accuracy of recalling dates of life events is improved by cross-referencing events recorded on the time-lines against each other and against an 'external' line of relevant major public events, for example the Second World War and the Coronation.

A validation study testing the lifegrid interview method was carried out by two of the researchers working on the present study.(2) Socio-demographic information collected retrospectively by lifegrid interview was compared with archived records of the same information collected from the same individuals 50 years previously. This information was recalled with a useful degree of accuracy and inaccurate recall, where it occurred, was not biased by social class or gender. Using data collected by the lifegrid method allowed calculation of the number of years exposure to a range of environmental factors known to be health-damaging and important in the creation of social class differences in health. The validation study found statistically significant social class differences in lifetime exposure to these environmental hazards by early old age.(3)

Lifecourse influences on health inequalities
The present study makes further use of the lifegrid method. Lifegrid interviews were carried out with a random sample of surviving members of a survey of child health originally conducted in the 1930s. Between 1937 and 1939, 1,352 families living in 16 sites across Britain took part in a social, dietary and clinical survey, carried out under the direction of Sir John Boyd Orr at the Rowett Research Institute. Altogether 3,762 children were surveyed and clinically examined.4 In 1997-98, we conducted interviews with nearly 300 of these survey participants now aged 63-78.

Combining lifegrid interview data with information recorded in the archives of the 1937-39 survey, our dataset includes details of childhood health and social circumstances, personal, residential, occupational and smoking histories and socio-economic circumstances through the lifecourse, from childhood to the present day. Our results show that disadvantage accumulates through the lifecourse; childhood disadvantage is associated with accumulating and greater levels of lifetime exposure to health-damaging environmental hazards. Lifetime hazard exposure is also associated with material and health disadvantage in early old age (full results are forthcoming).

Figure 2: segment of a completed lifegrid for a woman born in 1935

The potential of the lifegrid method
With adequate training, the method is easy to use. Recording data on the lifegrid time-lines rather than longhand facilitates probing, as well as allowing the interviewer to see at a glance the clustering of life events. For example, episodes of poor health were often found to coincide with stressful life events such as bereavement and retirement. As well as improving accuracy of recall, we found that cross-referencing between family, residential and occupational events improves interview rapport and increases enjoyment for interviewees. Using information given by the interviewee to frame further questions ("so if your son was born in 1955 you would have moved to 3 Acacia Road when he was aged 10, around the same time your husband was promoted. ..?") likens the interview to an episode from 'This Is Your Life' according to one interviewee. Others were surprised how much of their early lives they could remember, and how accurately they could date events in their lives, with events on time-lines corresponding with each other. Memories of the war years were especially vivid and many of our interviewees had stories of disrupted education, families torn apart through death or evacuation, and of both loving and abusive host families.

Like any method, the lifegrid method has its limitations. Firstly, subjects with very poor memories pose problems for researchers using any method. For example, a traumatic childhood meant that one interviewee could remember very little before his teen years. However, only 1% of our interviewees had a memory so poor that the interview was difficult. Secondly, the length of the recall period (from childhood to early old age) meant that lifetime hazard exposure was calculated as the number of complete years exposure. We found this was not sensitive enough to measure low lifetime exposure to a hazard with high toxicity, for example, being exposed to the nuclear testing at Christmas Island - a single exposure to a high dose of radiation.

Expressions of interest in the lifegrid method led to a training day held earlier this year, providing both social scientists and medical researchers with experience in its use. The lifegrid method has proved to be adaptable to a variety of topics (from long-term precursors of childhood bowel disease to social exclusion) and periods of recall (between 60 years to weekly recall), illustrating the flexibility of the method. With the increasing emphasis on public involvement in health needs assessment and the development of local and national health strategies, the lifegrid method may have broader policy-related uses. It provides a relatively low-cost way of collecting information on health hazards within community settings.

The lifegrid method will never replace the need for birth cohort data. However, the method will become increasingly useful as new questions emerge about the antecedents of health in old age.

Paula Holland, Lee Berney and David Blane work in the Division of Neuroscience at Imperial College of Science, Technology and Medicine, London University. George Davey Smith is based in the Department of Social Medicine, University of Bristol. This study 'Social Variations in Health in Early Old Age: Investigation of Precursors in a 60 Year Follow-Up Study' ended September 1998 and full results are forthcoming.

References:
1. For example, Kuh, D. and Ben-Shlomo, Y. (eds.) (1997) A Lifecourse Approach to Chronic Disease Epidemiology, Oxford : Oxford University Press.
2. Berney, L. R. and Blane, D. (1997) 'Collecting retrospective data: accuracy of recall after 50 years judged against historical records' Social Science and Medicine, 45 pp.1519-1525.
3. Blane, D., Montgomery, S. M. and Berney, L. R. (1998) 'Research note: social class differences in lifetime exposure to environmental hazards' Sociology of Health and Illness, 20, 4 pp.532-536.
4. Gunnell, D. L., Frankel, S., Nanchahal, K., Braddon, F. E. M. and Davey Smith, G. (1996) 'Lifecourse exposure and later disease: a follow-up study based on a survey of family diet and health in pre-war Britain (1937-1939)' Public Health, 110 pp.85-94.