Secular Trends in Dementia Prevalence and Incidence Worldwide: A Systematic Review

Article type: Research Article

Authors: Stephan, Blossom C.M.^{a; 1; *} | Birdi, Ratika^{a; 1} | Tang, Eugene Yee Hing^a | Cosco, Theodore D.^{b; c} | Donini, Lorenzo M.^d | Licher, Silvan^e | Ikram, M. Arfan^e | Siervo, Mario^f | Robinson, Louise^a

Affiliations: [a] Newcastle University Institute for Ageing and Institute of Health and Society, Newcastle University, UK | [b] Gerontology Research Centre, Simon Fraser University, Canada | [c] Oxford Institute of Population Ageing, University of Oxford, UK | [d] Department of Experimental Medicine, Medical Pathophysiology, Food Science and Endocrinology Section, Food Science and Human Nutrition Research Unit, Sapienza University of Rome, Italy | [e] Department of Epidemiology, Erasmus MC - University Medical Center Rotterdam, Rotterdam, The Netherlands | [f] Human Nutrition Research Centre, Institute of Cellular Medicine, Newcastle University, UK

Correspondence: [*] Correspondence to: Blossom Stephan, Newcastle University Institute for Ageing and Institute of Health & Society, Newcastle University, Newcastle Biomedical Research Building, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL, UK. Tel.: +44 0191 208 3811; E-mail: blossom.stephan@ncl.ac.uk.

Note: [1] These authors contributed equally to this work.

Abstract: Background:Time trends for dementia prevalence and incidence rates have been reported over the past seven decades in different countries and some have reported a decline. Objective:To undertake a systematic review to critically appraise and provide an evidence-based summary of the magnitude and direction of the global changes in dementia prevalence and incidence across time. Methods:Medline, EMBASE, and PsychINFO were searched for studies focused on secular trends in dementia prevalence and/or incidence until 18 December 2017. In total, 10,992 articles were identified and 43 retained. Results:Overall, prevalence rates are largely increasing (evidence primarily from record-based surveys and cohort studies in Japan, Canada, and France) or have remained stable (evidence primarily from cohort studies in Sweden, Spain and China). A significant decline in prevalence has however been reported in more recent studies (i.e., from 2010 onwards) from Europe (e.g., UK and Sweden) and the USA. Incidence rates have generally remained stable or decreased in China, Canada, France, Germany, Denmark, Sweden, the Netherlands, UK, and USA. An increase has only been reported in five countries: Italy, Japan, Wales, Germany, and the Netherlands. Only one study reported findings (stability in incidence) from a low and middle-income country using data from Nigeria. Conclusions:The evidence on secular trends in the prevalence and incidence of dementia is mixed including contradictory findings using different (and in some cases the same) datasets in some countries (e.g., the USA, UK, and Sweden). This making it difficult to draw concrete conclusions. However, declining trends recently observed in some high-income Western countries in the most recent two decades including the UK, USA, and Sweden are encouraging. Updated dementia prevalence and incidence estimates will inform public health and financial planning as well as development of prevention strategies.

Keywords: Dementia, incidence, prevalence, secular trends, systematic review

DOI: 10.3233/JAD-180375

Journal: Journal of Alzheimer's Disease, vol. 66, no. 2, pp. 653-680, 2018