English Longitudinal Study of Ageing | Our methods

Learn how each wave was carried out:

• 1 | Wave 0
• 2 | Wave 1 interviews
• 3 | Wave 2 interviews
• 4 | Wave 3 interviews
• 5 | Wave 4 interviews
• 6 | Wave 5 interviews
• 7 | Wave 6 interviews 
• 8 | Life history interview

Wave 0 is the name we have given to the creation of the survey's original sample. This sample was drawn from participants in the Health Survey for England when it was conducted in 1998, 1999 and 2001.

Altogether this gave us a sample of 23,000 households. Of these, 19,837 people were eligible to participate in the first wave of interviews for the English Longitudinal Study of Ageing. We considered a person eligible if they were aged 50 or over who had agreed to be re-contacted after taking part in the Health Survey for England.

All subsequent interview waves were based on Wave 0.

In Waves 3 and 4, when the youngest original sample members were approaching their 60s, we refreshed our sample with people just about to enter their 50s who had also participated in the Health Survey for England.

The major advantage of the Health Survey for England sampling source is that baseline data on respondents' health had already been collected before the first wave of interviews began.

Data users can compare Health Survey for England data and English Longitudinal Study of Aging data for those people who took part in the health survey and were eligible to take part in Wave 1 of this study.

Find our more about wave 0.

Wave 1 interviews were carried out with our Wave 0 sample during 2002-2003.

Approximately 12,000 productive interviews were achieved with people aged 50 and over living in private households in England. If a participant had a younger partner they were also interviewed, together with the core participant, in the same session using concurrent interviewing techniques.

The questionnaire was administered by computer aided personal interviewing. Both the core participants and the younger partners were also asked to complete a paper self-completion questionnaire at the end of their personal interview.

The questionnaire covered: individual and household characteristics; physical, cognitive, mental and psychological health; social participation and social support; housing, work, pensions, income and assets; and expectations for the future.

All data and documentation are available to download from the UK Data Archive and preliminary findings can be found in the report entitled "Health and lifestyles of the older population in England: The 2002 English Longitudinal Study of Ageing" (Marmot et al, 2003).

Find our more about wave 1.

Wave 2 interviews were conducted with all the households that gave productive interviews during Wave 1. Interviews were carried out 2 years after Wave 1 during 2004-2005.

In addition to computer aided personal interviewing and a self-completion questionnaire, Wave 2 interviews included a nurse visit.

At Wave 2, just over 9,400 eligible sample members were successfully interviewed and of these, around 7,600 core members went on to complete the nurse visit. Partners of the core members were not required to complete the nurse visit in this case.

Wave 2 interviews expanded on the questions asked during Wave 1. Questions were asked about: quality of health care received; household spending on leisure and clothing; perceptions of deprivation relative to others; perceptions of ageing; levels of literacy; perceived effort and reward for caregiving; and voluntary activities.

Link to report: Findings from the wave 2 survey can be found in "Retirement, health and relationships of the older population in England: The 2004 English Longitudinal Study of Ageing" (Banks et al., 2006).

Wave 3 interviews were conducted during 2006-2007.

We approached eligible sample members who had successfully interviewed in either or both of the earlier waves.

By this point the youngest members from Wave 0 were entering their early 60s, so we refreshed our Wave 3 sample with a cohort of people in their early 50s who had participated in the Health Survey for England between 2001 and 2004.

We selected participants aged between 50 to 53 and their older or younger partner if they had one. A total of 9,771 interviews were achieved at Wave 3.

Wave 3 interviews expanded on the questions asked in previous waves. Questions focused on: dental health, help with daily activities; access and use of both public and private transport; the state pensions forecasts that had recently been issued by the Government.

Wave 3 findings can be found in "Living in the 21st century: older people in England: The 2006 English Longitudinal Study of Ageing" (Banks et al., 2008).

Find out more about wave 3.

Wave 4 interviews were conducted during 2008-2009.

The sample for Wave 4 was drawn from the households that gave productive interviews during Wave 1 to Wave 3.

Another cohort was added at Wave 4 to refresh participants aged between 50 and 74. This cohort was drawn from 2006's Health Survey for England and includes cohabiting younger or older partners. A total of 11,050 main interviews took place at Wave 4.

In Wave 4 all interviews were conducted by CAPI face-to-face questionnaire. Like previous waves, participants were asked to complete a paper self-completion questionnaire at the end of their personal interview. We repeated the nurse visits first carried out during Wave 2. A total of 8,641 nurse interviews took place at Wave 4.

Wave 4 interviews expanded on the questions asked in previous waves. Questions focused on: Sleep patterns; women's health, mental health and eye/joint operations; state pension deferral and working beyond state pension age; property selling price and accommodation adaptations; Child Trust Funds; use of respite services; Television watching; and altruistic behaviour.

Wave 4 findings can be found in "Financial circumstances, health and well-being of the older population in England: The 2008 English Longitudinal Study of Ageing" (Banks et al., 2010)

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Wave 5 interviews

Wave 5 interviews were conducted during 2010-2011.

The sample for Wave 5 was drawn from eligible sample members who had been successfully interviewed at one or more of the previous waves.

In 2007 we conducted interviews with a subgroup of participants to find out about their lives before they were interviewed for the Health Survey for England. We called these interviews Life History Interviews. Approximately 7,800 of these interviews were achieved.

The Life History Interviews collected data across a number of different topics including: children by birth and adoption; fertility; cohabitation and important non-cohabiting relationships; housing and geographical mobility; living situation when they were 10 years old; jobs and earnings; health including injuries, childhood health, smoking and gynaecology; childhood relationship with parents; and other important and difficult events in their lives.

Next steps
You can read more about the results of wave 0, results of wave 1 and results of wave 3, results of wave 4, results of wave 5.