With increasing life-expectancy, disability associated with the many different health conditions has become a major health issue.
However the extent of limitations in activities is not simply explained by the health condition – people with minor conditions can have major limitations whereas others with serious health conditions appear to have only trivial limitations.
Other important factors are the physical environment, social circumstances, support available, the individual's way of managing their emotions as well as their style of thinking about their condition and activities.
We investigate how these factors determine the resulting disablement in large group longitudinal studies and in intensive (EMA) studies of single individuals. We have developed a theoretical model that integrates the biomedical factors with the behavioural factors and have demonstrated that this integrated model is a better predictor than either the health condition or the psychological factors on their own.
Our work connects with the interdisciplinary focus of this field by linking our theoretical and empirical work to the WHO ICF model (International Classification of Functioning, Disability and Health). However, this model was untestable without good measures of key components (impairment, activity limitations and participation restrictions) and we have shown that existing measures assess a mixture (see graphic). Based on existing health outcome measures, we have developed the Aberdeen pure measures of ICF components using classical test theory, item response theory and discriminant content validity approaches and this has enabled us to publish tests of this theory as well as the integrated model.
Existing health outcomes measures assess a mixture of ICF components: Impairment (red), Activity Limitations (green) and Participation Restrictions (blue)
Using our theory and understanding of the process of disablement we aim to develop and evaluate interventions that reduce disability and its impact. E.g.
Johnston M, Bonetti D, Joice S, Pollar B, Morrision V, Francis JJ, MacWalter R. (2007). Recovery from disability after stroke as a target for a behavioural intervention: Results of a randomised controlled trial. Disability & Rehabilitation, 29, 1117-1127.
- Johnston, M. & Dixon, D. (2014). ‘Developing an integrated biomedical and behavioural theory of functioning and disability: adding models of behaviour to the ICF framework’. Health Psychology Review, vol. 8, no. 4, pp. 381–403.
[Online] DOI: 10.1080/17437199.2013.855592
- Pollard, B., Dixon, D. & Johnston, M. (2014). ‘Does the impact of osteoarthritis vary by age, gender and social deprivation? A community study using the International Classification of Functioning, Disability and Health’. Disability & Rehabilitation, vol 36, no. 17, pp. 1445-1451.
[Online] DOI: 10.3109/09638288.2013.847123
- Quinn, F., Johnston, M. & Johnston, D.W. (2013) ‘Testing an Integrated Behavioural and Biomedical Model of Disability in N-of-1 Studies with Chronic Pain’. Psychology & Health.
[Online] DOI: 10.1080/08870446.2013.814773
- Pollard, B., Dixon, D., Dieppe, P. & Johnston, M. (2009). ‘Measuring the ICF components of Impairment, Activity Limitation and Participation Restriction: an item analysis using classical test theory and item response theory. Health and Quality of Life Outcomes 2009, 7:41.
[Online] DOI: http://dx.doi.org/10.1186/1477-7525-7-41
- Cooper, CL., Phillips, LH., Johnston, M., Whyte, M. & MacLeod, MJ. (2014). 'The role of emotion regulation on social participation following stroke'. British Journal of Clinical Psychology.
[Online] DOI: 10.1111/bjc.12068
- Cooper, CL., Phillips, LH., Johnston, M., Radlak, B., Hamilton, S. & McLeod, MJ. (2014). 'Links between emotion perception and social participation restriction following stroke'. Brain Injury, vol 28, no. 1, pp. 122-126.
[Online] DOI: 10.3109/02699052.2013.848379
- Ietswaart, M., Johnston, M., Dijkerman, HC., Joice, S., Scott, CL., MacWalter, RS. & Hamilton, SJC. (2011). 'Mental practice with motor imagery in stroke recovery: randomized controlled trial of efficacy'. Brain, vol 134, no. 5, pp. 1373-1386.
[Online] DOI: 10.1093/brain/awr077
- Gray, NM., Allan, JL., Murchie, P., Browne, S., Hall, S., Hubbard, G., Johnston, M., Lee, AJ., McKinley, A., Macleod, U., Presseau, J., Samuel, L., Wyke, S. & Campbell, NC. (2013). 'Developing a community-based intervention to improve quality of life in people with colorectal cancer: a complex intervention development study'. BMJ Open, vol 3, no. 4, e002596.
[Online] DOI: 10.1136/bmjopen-2013-002596