Dementia prevention in low-income and middle-income countries: a cautious step forward
Authors: Richard Walker, Stella-Maria Paddick
Journal: The Lancet Global Health (2019)

The burden of dementia worldwide is increasing, particularly in low-income and middle-income countries (LMICs). In the absence of curative treatments, dementia risk reduction and primary prevention strategies are recommended in policy statements, such as those of the G8 and WHO on reduction of the global dementia burden1WHOGlobal action plan on the public health response to dementia 2017–2025.http://www.g8.utoronto.ca/healthG8/2013-dementia-declaration.htmlDate accessed: March 28, 2019Google Scholar and public health guidelines, but these strategies are under-researched. The Article by Mukadam and colleagues2Mukadam N Sommerlad A Huntley J Livingston G Population attributable fractions for risk factors for dementia in low-income and middle-income countries: an analysis using cross-sectional survey data.Lancet Glob Health. 2019; 7: e596-e603Summary Full Text Full Text PDF PubMed Scopus (149) Google Scholar is therefore timely given that the authors try to identify the population attributable fraction (PAF) for potentially modifiable risk factors in LMICs, which could then lead to potential prevention strategies. In the Article,2Mukadam N Sommerlad A Huntley J Livingston G Population attributable fractions for risk factors for dementia in low-income and middle-income countries: an analysis using cross-sectional survey data.Lancet Glob Health. 2019; 7: e596-e603Summary Full Text Full Text PDF PubMed Scopus (149) Google Scholar Mukadam and colleagues look at the nine risk factors that have been identified as the most important worldwide,3Livingston G Sommerlad A Orgeta V et al.Dementia prevention, intervention, and care.Lancet. 2017; 390: 2673-2734Summary Full Text Full Text PDF PubMed Scopus (3122) Google Scholar and evaluate these factors in a large dataset incorporating several representative LMIC cohorts at different stages of economic development as part of the 10/66 collaboration, an initiative that has transformed knowledge of dementia in LMIC settings. The authors show that the overall PAF for dementia was 57% in their cohort of Latin American countries, 41% in China, and 41% in India compared with previous data from high-income countries (HICs) of 35%. This result raises the possibility that in LMIC settings that are rapidly undergoing nutritional and demographic transition, risk reduction strategies could have a great effect. These data add to the knowledge on dementia globally, but some caution must be exercised. As noted elsewhere,4Kivimäki M Singh-Manoux A Prevention of dementia by targeting risk factors.Lancet. 2018; 391: 1574-1575Summary Full Text Full Text PDF PubMed Scopus (20) Google Scholar PAF calculations depend on strength of association but are not necessarily causal relationships. Some risk factors, such as hearing loss, social interaction, or depression, might be features of prodromal disease rather than modifiable risk factors.4Kivimäki M Singh-Manoux A Prevention of dementia by targeting risk factors.Lancet. 2018; 391: 1574-1575Summary Full Text Full Text PDF PubMed Scopus (20) Google Scholar Similarly, caution should be exercised in relation to the data itself. The diagnosis of dementia was based on the 10/66 diagnostic criteria, which, although more culturally relevant in some settings, might also overestimate diagnoses of dementia, particularly in populations with very low literacy.5Paddick SM Longdon AR Kisoli A et al.Dementia prevalence estimates in sub-Saharan Africa: comparison of two diagnostic criteria.Glob Health Act. 2013; 6: 1-7Google Scholar Furthermore, although large, the 10/66 dataset includes few data from sub-Saharan Africa, and therefore might not be truly representative of LMICs worldwide. The quality of risk factor data used might differ from that collected in HIC studies, in that theses data rely on self-report and are less likely to be accurate in LMICs, where health-care coverage might be limited and conditions might remain undiagnosed. For example, people with hypertension who have never had their blood pressure measured will not have been diagnosed, and therefore the prevalence of hypertension is likely to be an underestimate. And yet as challenging as it is, in terms of prevention of dementia, diagnosis and treatment of hypertension, which is also the most important risk factor for overall mortality worldwide, is likely to have the greatest effect.6Lozano R Naghavi M Foreman K et al.Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010.Lancet. 2012; 380: 2095-2128Summary Full Text Full Text PDF PubMed Scopus (9924) Google Scholar Likewise, low educational attainment has a large PAF for dementia, in part because of its high worldwide prevalence. However, low education might have a different meaning or threshold in LMICs compared with HICs, and low education and childhood disadvantage are difficult to disentangle. Childhood disadvantage (low nutrition, childhood adversity, and low educational attainment) is associated with poor cognitive function in LMIC settings (and in disadvantaged groups in HICs).7Zhang Z Liu J Li L Xu H The long arm of childhood in China: early-life conditions and cognitive function among middle-aged and older adults.J Aging Health. 2018; 30: 1319-1344Crossref PubMed Scopus (44) Google Scholar, 8Radford K Delbaere K Draper B et al.Childhood stress and adversity is associated with late-life dementia in Aboriginal Australians.Am J Geriatr Psychiatr. 2017; 25: 1097-1106Summary Full Text Full Text PDF PubMed Scopus (65) Google Scholar This so-called life course approach to cognition is complex and might involve several societal and environmental factors at different timepoints in each population.9Wu YT Beiser AS Breteler MM et al.The changing prevalence and incidence of dementia over time—current evidence.Nat Rev Neurol. 2017; 13: 327Crossref PubMed Scopus (349) Google Scholar Accuracy of self-report of previous episodes of depression might also be limited in settings in which mental health-care is scarce and cultural understanding of depression might differ. As Mukadam and co-workers2Mukadam N Sommerlad A Huntley J Livingston G Population attributable fractions for risk factors for dementia in low-income and middle-income countries: an analysis using cross-sectional survey data.Lancet Glob Health. 2019; 7: e596-e603Summary Full Text Full Text PDF PubMed Scopus (149) Google Scholar acknowledge, difficulties in cross-cultural understanding of questions about depression might have influenced the low reported prevalence in India and China. Although these data provide a glimpse of the dementia situation in LMICs, some questions remain. One question is about the most cost-effective ways of addressing identified modifiable risk factors in LMICs. In particular, there is a need for culturally appropriate tools for a timely diagnosis of dementia in LMICs, particularly when taking illiteracy into consideration.3Livingston G Sommerlad A Orgeta V et al.Dementia prevention, intervention, and care.Lancet. 2017; 390: 2673-2734Summary Full Text Full Text PDF PubMed Scopus (3122) Google Scholar Given that most people with dementia now live in LMICs, interventions are key, alongside prevention strategies.3Livingston G Sommerlad A Orgeta V et al.Dementia prevention, intervention, and care.Lancet. 2017; 390: 2673-2734Summary Full Text Full Text PDF PubMed Scopus (3122) Google Scholar The WHO 2017–25 public health dementia plan aims to implement dementia awareness-raising campaigns in 100% of countries worldwide.1WHOGlobal action plan on the public health response to dementia 2017–2025.http://www.g8.utoronto.ca/healthG8/2013-dementia-declaration.htmlDate accessed: March 28, 2019Google Scholar This strategy is a start, but a long way from the access to pharmaceutical and non-pharmaceutical interventions, support, and advice that is needed for people living with dementia and their carers10Ferri CP Jacob KS Dementia in low-income and middle-income countries: different realities mandate tailored solutions.PLoS Med. 2017; 14: e1002271Crossref PubMed Scopus (57) Google Scholar in LMICs, where scarce health and human resources mandate a task-shifting approach of integrating care for dementia alongside other psychiatric conditions into chronic disease clinics, delivered by non-specialist health workers.11WHOmhGAP intervention guide for mental, neurological and substance use disorders in non-specialized health settings: mental health Gap Action Programme (mhGAP)–version 2.0. World Health Organization, Geneva2016Google Scholar Encouragingly, early evidence suggests low-resource interventions such as cognitive stimulation therapy (a psychosocial intervention that can be delivered by non-specialists) can be successful in LMIC settings.12Paddick SM Mkenda S Mbowe G et al.Cognitive stimulation therapy as a sustainable intervention for dementia in sub-Saharan Africa: feasibility and clinical efficacy using a stepped-wedge design.Int Psychogeriatr. 2017; 29: 979-989Crossref PubMed Scopus (30) Google Scholar Potentially modifiable risk factors for dementia in LMICs have been identified and are amenable to interventions. Identification and control of hypertension would have the greatest effect. We declare no competing interests. Population attributable fractions for risk factors for dementia in low-income and middle-income countries: an analysis using cross-sectional survey dataThe dementia prevention potential in India, China, and this sample of Latin American countries is large, and greater than in high-income countries. Less education in early life, hypertension, hearing loss, obesity, and physical inactivity have particularly high PAFs and could be initial targets for dementia prevention strategies. Full-Text PDF Open Access