Complex interventions

Figures & data

Table 1. Key methods and tools to analyse complexity in intervention design, context, and implementation.

Method, concept or tool	Use for analysing complexity in a systematic review	Examples of application within SEP literature
Intervention Complexity Assessment Tools for Systematic Reviews (iCAT_SR). Tool based on ten dimensions of intervention complexity (Lewin et al., 2017).	Guiding systematic and detailed assessment and categorisation of levels of complexity to provide an overall understanding of intervention complexity, which can be represented visually.	Blackburn et al. (2020); Jones et al. (2019)
Behaviour Change Taxonomy (Michie et al., 2013). Extensive taxonomy of 93 distinct behaviour change techniques (BCTs) that represent the active content of interventions.	Supporting consistent identification and comparison of the components or ‘active ingredients’ that interventions are built on. BCTs can be used in subgroup analysis to identify effective components, such as through meta-regression.	Howlett et al. (2019); Knittle et al. (2018)
Theory Coding Scheme (Michie & Prestwich). 19-item tool to assess the extent which interventions are theory-based.	Supporting consistent identification and comparison of the use of theory in intervention design and implementation.	Allan et al. (2018); Bentley et al. (2020)
Meta-regression (Baker et al., 2009) to explore the relative effectiveness of different intervention components.	Identifying the components of interventions (such as BCTs) that appear effective. Other advanced statistical methods such as network meta-analysis can be used to further explore complexity in intervention design.	Eckerstorfer et al. (2018); Howlett et al. (2019)
Better reporting of interventions: template for intervention description and replication (TIDieR) checklist and guide. 12-item reporting standards to guide detailed reporting of interventions (Hoffmann et al., 2014)	Guiding consistent extraction of intervention details including procedures, setting, delivery, implementation, and process outcomes.	Bentley et al. (2020); Klempel et al. (2021)
Logic models exploring the underlying theories of interventions and system-level influences intervention outcomes (Petticrew et al., 2019)	Supporting understanding of how the wider system works, and how context influences intervention implementation and outcomes. Identifying outcomes to include in a review. Communicating complexity to readers.	Kahn et al. (2002); Motamed-Jahromi and Kaveh (2021)
Realist synthesis (Pawson & Bellamy, 2006) to explore the underlying causal mechanisms that explain why interventions work or do not work.	Supporting understand of how environmental context and intervention implementation factors influences the effectiveness of findings. Can be carried out alongside a review of effectiveness outcomes.	Leone and Pesce (2017); Pesce et al. (2021)
Measures of factors influencing how interventions are implemented or experienced. For example, dimensions of implementation (Cargo et al., 2018) including quantitative and qualitative measures.	Identifying implementation outcomes to help explain variation in effects. Typically included in reviews of qualitative or mixed-methods evidence, but can be included alongside a review of effectiveness outcomes.	Farrance et al. (2016); Naylor et al. (2015)

Lewin, S., Hendry, M., Chandler, J., Oxman, A. D., Michie, S., Shepperd, S., & Noyes, J. (2017). Assessing the complexity of interventions within systematic reviews: Development, content and use of a new tool (iCAT_SR). BMC Medical Research Methodology, 17(1), 76. https://doi.org/https://doi.org/10.1186/s12874-017-0349-x

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Blackburn, N. E., Wilson, J. J., McMullan, I. I., Caserotti, P., Giné-Garriga, M., Wirth, K., & Tully, M. A. (2020). The effectiveness and complexity of interventions targeting sedentary behaviour across the lifespan: A systematic review and meta-analysis. International Journal of Behavioral Nutrition and Physical Activity, 17(1), 53. https://doi.org/https://doi.org/10.1186/s12966-020-00957-0

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Jones, R. A., Blackburn, N. E., Woods, C., Byrne, M., van Nassau, F., & Tully, M. A. (2019). Interventions promoting active transport to school in children: A systematic review and meta-analysis. Preventive Medicine, 123, 232–241. https://doi.org/https://doi.org/10.1016/j.ypmed.2019.03.030

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Michie, S., Richardson, M., Johnston, M., Abraham, C., Francis, J., Hardeman, W., & Wood, C. E. (2013). The behavior change technique taxonomy (v1) of 93 hierarchically clustered techniques: Building an international consensus for the reporting of behavior change interventions. Annals of Behavioral Medicine, 46(1), 81–95. https://doi.org/https://doi.org/10.1007/s12160-013-9486-6

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Howlett, N., Trivedi, D., Troop, N. A., & Chater, A. M. (2019). Are physical activity interventions for healthy inactive adults effective in promoting behavior change and maintenance, and which behavior change techniques are effective? A systematic review and meta-analysis. Translational Behavioral Medicine, 9(1), 147–157. https://doi.org/https://doi.org/10.1093/tbm/iby010

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Knittle, K., Nurmi, J., Crutzen, R., Hankonen, N., Beattie, M., & Dombrowski, S. U. (2018). How can interventions increase motivation for physical activity? A systematic review and meta-analysis. Health Psychology Review, 12(3), 211–230. https://doi.org/https://doi.org/10.1080/17437199.2018.1435299

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Allan, V., Vierimaa, M., Gainforth, H. L., & Côté, J. (2018). The use of behaviour change theories and techniques in research-informed coach development programmes: A systematic review. International Review of Sport and Exercise Psychology, 11(1), 47–69. https://doi.org/https://doi.org/10.1080/1750984X.2017.1286514

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Bentley, M. R. N., Mitchell, N., & Backhouse, S. H. (2020). Sports nutrition interventions: A systematic review of behavioural strategies used to promote dietary behaviour change in athletes. Appetite, 150, 104645. https://doi.org/https://doi.org/10.1016/j.appet.2020.104645

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Baker, W. L., White, C. M., Cappelleri, J. C., Kluger, J., & Coleman, C. I. (2009). Understanding heterogeneity in meta-analysis: The role of meta-regression. International Journal of Clinical Practice, 63(10), 1426–1434. https://doi.org/https://doi.org/10.1111/j.1742-1241.2009.02168.x

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Eckerstorfer, L. V., Tanzer, N. K., Vogrincic-Haselbacher, C., Kedia, G., Brohmer, H., Dinslaken, I., & Corcoran, K. (2018). Key elements of mHealth interventions to successfully increase physical activity: Meta-regression. JMIR mHealth and uHealth, 6(11), 2291–5222. https://doi.org/https://doi.org/10.2196/10076

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Hoffmann, T. C., Glasziou, P. P., Boutron, I., Milne, R., Perera, R., Moher, D., & Michie, S. (2014). Better reporting of interventions: Template for intervention description and replication (TIDieR) checklist and guide. BMJ, 348, g1687. https://doi.org/https://doi.org/10.1136/bmj.g1687

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Klempel, N., Blackburn, N. E., McMullan, I. L., Wilson, J. J., Smith, L., Cunningham, C., & Tully, M. A. (2021). The effect of chair-based exercise on physical function in older adults: A systematic review and meta-analysis. International Journal of Environmental Research and Public Health, 18(4), 1902. https://doi.org/https://doi.org/10.3390/ijerph18041902

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Petticrew, M., Knai, C., Thomas, J., Rehfuess, E. A., Noyes, J., Gerhardus, A., & McGill, E. (2019). Implications of a complexity perspective for systematic reviews and guideline development in health decision making. BMJ Global Health, 4(Suppl 1), e000899. https://doi.org/https://doi.org/10.1136/bmjgh-2018-000899

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Kahn, E. B., Ramsey, L. T., Brownson, R. C., Heath, G. W., Howze, E. H., Powell, K. E., & Corso, P. (2002). The effectiveness of interventions to increase physical activity: A systematic review. American Journal of Preventive Medicine, 22(4), 73–107. https://doi.org/https://doi.org/10.1016/S0749-3797(02)00434-8

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Motamed-Jahromi, M., & Kaveh, M. H. (2021). Effective interventions on improving elderly's independence in activity of daily living: A systematic review and logic model. Frontiers in Public Health, 8, 516151. https://doi.org/https://doi.org/10.3389/fpubh.2020.516151

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Pawson, R., & Bellamy, J. L.. (2006). Realist synthesis: An explanatory focus for systematic review. In J. Popay (Ed.), Moving Beyond Effectiveness in Evidence Synthesis (pp. 83–94). London: National Institute for Health and Clinical Excellence.

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Leone, L., & Pesce, C. (2017). From delivery to adoption of physical activity guidelines: Realist synthesis. International Journal of Environmental Research and Public Health, 14(10), 1193. https://doi.org/https://doi.org/10.3390/ijerph14101193

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Pesce, C., Vazou, S., Benzing, V., Álvarez-Bueno, C., Anzeneder, S., Mavilidi, M. F., & Schmidt, M. (2021). Effects of chronic physical activity on cognition across the lifespan: A systematic meta-review of randomized controlled trials and realist synthesis of contextualized mechanisms. International Review of Sport and Exercise Psychology, 1–39. https://doi.org/https://doi.org/10.1080/1750984X.2021.1929404

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Cargo, M., Harris, J., Pantoja, T., Booth, A., Harden, A., Hannes, K., & Noyes, J. (2018). Cochrane Qualitative and Implementation Methods Group guidance series—paper 4: Methods for assessing evidence on intervention implementation. Journal of Clinical Epidemiology, 97, 59–69. https://doi.org/https://doi.org/10.1016/j.jclinepi.2017.11.028

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Farrance, C., Tsofliou, F., & Clark, C. (2016). Adherence to community based group exercise interventions for older people: A mixed-methods systematic review. Preventive Medicine, 87, 155–166. https://doi.org/https://doi.org/10.1016/j.ypmed.2016.02.037

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Naylor, P.-J., Nettlefold, L., Race, D., Hoy, C., Ashe, M. C., Wharf Higgins, J., & McKay, H. A. (2015). Implementation of school based physical activity interventions: A systematic review. Preventive Medicine, 72, 95–115. https://doi.org/https://doi.org/10.1016/j.ypmed.2014.12.034

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