Background Although cognitive performance levels in old age have increased in most countries, recent evidence documents a slowing down or even decline in cohort gains in highly developed countries. The aim of this study was to assess trends and determinants in secular cohort gains in cognitive functioning among older individuals and whether cohort gains are levelling off in most advanced countries.
Methods Data for individuals aged between 50 and 84 years from the Survey of Health, Ageing and Retirement in Europe in 10 European countries between 2004 and 2013 (n=92 739) were used to assess country and age-specific changes in immediate word recall. Multivariate random intercept models were used to assess associations between secular cohort changes in immediate word recall, initial performance levels and changes in country-level socio-demographic characteristics.
Results Performance in immediate word recall improved in all countries between 2004 and 2013 (from 4.40 to 5.08 words, P<0.05). However, secular cohort gains were significantly smaller in countries with initially higher performance levels (coeff.=−0.554, 95% CI −0.682 to –0.426). Changes in socio-demographic and health conditions, including decreases in cardiovascular disease, physical activity and educational achievement, were associated with larger secular cohort gains.
Conclusions Results may either reflect that some countries are approaching the limits of cognitive plasticity, are slowing in their progress or that societal structures have not yet been optimised to improve cognitive abilities in midlife and beyond, or a combination of these interpretations.
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Contributors VS had the idea for the study. UMS developed the conceptual framework. JMK did the initial analysis. PH performed the final analyses of the data and compiled the figures and tables. All authors interpreted the results and contributed to writing the final version of the manuscript.
Funding This paper uses data from SHARE waves 1 and 5 (DOIs: 10.6103/SHARE.w1.600, 10.6103/SHARE.w2.600, 10.6103/SHARE.w5.600). The SHARE data collection has been primarily funded by the European Commission through FP5 (QLK6-CT-2001-00360), FP6 (SHARE-I3: RII-CT-2006-062193, COMPARE: CIT5-CT-2005-028857, SHARELIFE: CIT4-CT-2006-028812) and FP7 (SHARE-PREP: no. 211909, SHARE-LEAP: no. 227822, SHARE M4: N°261982). Additional funding from the German Ministry of Education and Research, the Max Planck Society for the Advancement of Science, the U.S. National Institute on Aging (U01_AG09740-13S2, P01_AG005842, P01_AG08291, P30_AG12815, R21_AG025169, Y1-AG-4553-01, IAG_BSR06-11, OGHA_04-064, HHSN271201300071C) and from various national funding sources is gratefully acknowledged (see www.share-project.org). This work was partly supported by the Research Council of Norway through its Centres of Excellence funding scheme, project number 262700 and through grant “The burden of obesity in Norway: morbidity, mortality, health service use, and productivity loss” project number 250335/F20. PH was supported by a David E Bell Fellowship from the Harvard Center for Population and Development Studies.
Patient consent Detail has been removed from this these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.
Ethics approval The study uses publicly available survey data which were collected after obtaining ethical approval from national review boards and consent of participants.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Additional data are available on the journal’s homepage.
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