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Socioeconomic inequalities in physical and cognitive functioning: cross-sectional evidence from 37 cohorts across 28 countries in the ATHLOS project
  1. Denes Stefler1,
  2. Matthew Prina2,
  3. Yu-Tzu Wu2,
  4. Albert Sánchez-Niubò3,4,
  5. Wentian Lu1,
  6. Josep Maria Haro3,4,
  7. Michael Marmot1,
  8. Martin Bobak1
  1. 1 Department of Epidemiology and Public Health, University College London, London, UK
  2. 2 Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
  3. 3 Research, Innovation and Teaching Unit, Parc Sanitari Sant Joan de Deu, Sant Boi de Llobregat, Barcelona, Spain
  4. 4 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
  1. Correspondence to Dr Denes Stefler, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, UK; denes.stefler{at}ucl.ac.uk

Abstract

Background Physical and cognitive functioning in older age follows a socioeconomic gradient but it is unclear whether the strength of the association differs between populations. Using harmonised data from an international collaboration of cohort studies, we assessed socioeconomic inequalities in physical and cognitive functioning and explored if the extent of inequalities varied across countries based on their economic strength or wealth distribution.

Methods Harmonised data from 37 population-based cohorts in 28 countries were used, with an overall sample size of 126 765. Socioeconomic position of participants was indicated by education and household income. Physical functioning was assessed by self-reported mobility and activities of daily living; and cognitive functioning by memory and verbal fluency tests. Relative (RII) and slope (SII) index of inequality were calculated in each cohort, and their association with the source country’s Gross Domestic Product (GDP) and Gini-index was assessed with correlation and cross-level interaction in multilevel models.

Results RII and SII values indicated consistently higher risk of low physical and cognitive functioning in participants with lower education or income across cohorts. Regarding RII, there were weak but statistically significant correlations and interactions with GDP and Gini-index, suggesting larger inequalities in countries with lower Gini-index and higher GDP. For SII, no such correlations were observed.

Conclusion This study confirms that socioeconomic inequalities in physical and cognitive functioning exist across different social contexts but the magnitude of these inequalities varies. Relative inequalities appear to be larger in higher-income countries but it remains to be seen whether such observation can be replicated.

  • physical function
  • cognition
  • ageing
  • social inequalities

Data availability statement

Data are available in a public, open access repository. Data are available on reasonable request. Documentation and metadata of the ATHLOS harmonisation process can be accessed at: https://github.com/athlosproject/athlos-project.github.io; https://athlos.pssjd.org. The original cohort data are publicly available or can be accessed via contacting the study management teams on reasonable request.

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Data availability statement

Data are available in a public, open access repository. Data are available on reasonable request. Documentation and metadata of the ATHLOS harmonisation process can be accessed at: https://github.com/athlosproject/athlos-project.github.io; https://athlos.pssjd.org. The original cohort data are publicly available or can be accessed via contacting the study management teams on reasonable request.

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Footnotes

  • Contributors DS, MM and MB developed the original idea and designed the analytical approach. AMP, Y-TW and WL made substantial contributions to the analytical design and the interpretation of results. AS-N organised the data harmonisation procedures, and JMH was responsible for the management of the ATHLOS project. All authors contributed to the writing of the manuscript and approved the final version of the text.

  • Funding This work was supported by the 5 years Ageing Trajectories of Health: Longitudinal Opportunities and Synergies (ATHLOS) project. The ATHLOS project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 635 316.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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