Scottish Longitudinal Study
Development & Support Unit

Current Projects

Project Title:

Exploration of the new ‘Health Conditions’ question in the 2011 Scottish Census and comparison with the ‘Limited Activity’ (LLTI) question at 2001 and 2011

Project Number:



Fiona Cox (University of St Andrews)
Alan Marshall (University of St Andrews)

Start Date:

22 Sept 2015



Prior to the inclusion of the ‘Health Condition’ question in the 2011 Scottish and Northern Ireland Censuses, researchers using the SLS or NILS had to rely on the Limiting Long-Term Illness (LLTI) variable as their best proxy for disability.1,2

This is far from ideal for several reasons:

  • some people with disabilities may not consider their activities ‘limited’;
  • the LLTI question lacks information on the type of impairment the person has;
  • ‘LLTI’ may include illnesses researchers would not have included in their definition of ‘impairment’ or ‘disability’; and
  • this relatively indirect proxy may have acted as a disincentive for disability researchers to use the SLS for their analyses.

Testing and comparing the new questions with the old is important for three main reasons. Firstly, previous SLS and NILS researchers who relied on the LLTI proxy will find it valuable to know if this can be validated as representative of the population they were trying to measure. Secondly, new researchers will have an indication of whether the LLTI gives a usable indicator of past impairments. Finally, the question of how good a proxy the LLTI question is remains important for ONS LS researchers, since the 2011 Census for England and Wales did not include a detailed question on impairment type, and LLTI remains the only available proxy for disability.3-6


Whilst the 1991 and 2001 Censuses contained only one question relating to Limiting Long-term Illness (LLTI) or disability, the 2011 Scottish Census introduced a second question allowing respondents to give details of their impairments and health conditions. In addition, the LLTI question at 2011 now allowed people to say whether their daily activities were limited ‘a little’ or ‘a lot’.

Prior to 2011 the LLTI question was the best available proxy for disability in the SLS dataset, and it continues to serve this purpose in the ONS LS for England and Wales. The main purpose of the present research is to attempt to explore how well the ‘LLTI’ questions capture this population, by exploring the following research questions:

  1. In terms of demographics, how do people who said they had an LLTI at 2001 compare with those who listed a health condition at 2011? What are the differences, and are there populations not represented by relying only on LLTI as an indicator?
  2. Comparing responses to the 2001 and 2011 LLTI questions: is there any indication that at 2001 people only reported that they had an LLTI if it limited them ‘a lot’? Does the inclusion of the Health Condition question at 2011 change the way in which people choose to answer the LLTI question?

Comparing the 2011 LLTI and Health Condition questions, which types of impairment are more likely to coincide with LLTI responses of ‘a lot’ and ‘a little’?


1. Millard, A. & McCartney, G. SLS project 2012_003 – ‘Equality, Inequality and health in Scotland.’

2. Popham, F. SLS project 2007_003 – ‘Permanent sickness, returning to employment and health.’

3. White, C. & Edgar, G. (2010) Inequalities in disability-free life expectancy by social class and area type: England, 2001–03. Health Statistics Quarterly, 45(Spring), 57 - 80. Office for National Statistics. 24 February 2010

4. Spencer, N., Blackburn, C. & Read, J. (2011) Exploring the association between childhood limiting long-term illness/disability and social disadvantage: Does social disadvantage precede or follow the onset of childhood limiting long-term illness/disability? Society for Social Medicine 55th Annual Scientific Meeting, University of Warwick, 14 - 16 September 2011

5. Spencer, N., Blackburn, C. & Read, J. (2011) Does social disadvantage precede or follow the onset of childhood limiting long term illness/disability? Society for Social Medicine 55th Annual Scientific Meeting, University of Warwick, 14 - 16 September 2011

6. Blackburn, C.M., Spencer, N.J. & Read, J.M. (2013) Is the onset of disabling chronic conditions in later childhood associated with exposure to social disadvantage in earlier childhood? A prospective cohort study using the ONS Longitudinal Study for England and Wales. BMC Pediatrics, 13(1), 1471-2431, 26 June 2013

Related Outputs (viewable on CALLS Hub):

Explore the variables held in the SLS data dictionary.

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