Potential for dementia prevention in Latin America and Africa based on population-attributable fraction estimates
Authors: Déborah Oliveira, Cleusa P Ferri
Journal: The Lancet Global Health (2019)

We read with interest the study by Mukadam and colleagues1Mukadam 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 (85) Google Scholar in The Lancet Global Health, which reported population-attributable fractions (PAFs) for nine risk factors for dementia, based on data from the 10/66 Dementia Research Group studies carried out in eight low-income and middle-income countries (LMICs). We also welcome the commentary by Walker and Paddick,2Walker R Paddick SM Dementia prevention in low-income and middle-income countries: a cautious step forward.Lancet Glob Health. 2019; 7: e538-e539Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar highlighting the scarcity of data from Africa and suggesting a cautious approach to using PAF, especially given that the PAFs are based on self-reported cross-sectional data in 10/66, and that the number of cases of dementia may be overestimated in this cohort. Both study and commentary shed light on an urgent issue, which is the reduction of the number of dementia cases in LMICs, where most people with dementia live, and where the burden of dementia is expected to increase rapidly. We would like to add to this discussion by referring to our study published online in the Journal of Alzheimer's Disease in January, 2019,3Oliveira D Jun Otuyama L Mabunda D et al.Reducing the number of people with dementia through primary prevention in Mozambique, Brazil, and Portugal: an analysis of population-based data.J Alzheimers Dis. 2019; (published online Jan 12.)DOI:10.3233/JAD-180636Crossref Scopus (13) Google Scholar in which we estimated adjusted PAFs for similar risk factors for Brazil, Mozambique, and Portugal, and the effect of their reduction on projections of dementia cases using previously published methods.4Norton S Matthews FE Barnes DE Yaffe K Brayne C Potential for primary prevention of Alzheimer's disease: an analysis of population-based data.Lancet Neurol. 2014; 13: 788-794Summary Full Text Full Text PDF PubMed Scopus (1250) Google Scholar, 5Barnes DE Yaffe K The projected effect of risk factor reduction on Alzheimer's disease prevalence.Lancet Neurol. 2011; 10: 819-828Summary Full Text Full Text PDF PubMed Scopus (1596) Google Scholar Our study was based on seven modifiable risk factors for dementia (low education, physical inactivity, midlife hypertension and obesity, depression, smoking, and diabetes), thus including the same factors as those studied by Mukadam and colleagues,1Mukadam 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 (85) Google Scholar except for social isolation and hearing impairment. Although Mukadam and colleagues1Mukadam 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 (85) Google Scholar showed that the adjusted PAFs were 39·5% in China, 41·2% in India, and 55·8% in Latin America, we found substantially lower PAFs—24·4% in Mozambique and 32·3% in Brazil. Even removing the two risk factors not included in our study, the adjusted PAF for Latin America in Mukadam and colleagues’ study would still be higher (approximately 48%). Brazil was not included in their analysis, however Brazil is the most populous country in Latin America and therefore the discrepancy in the adjusted PAFs found between the two studies is of importance. This might be related to the issue raised by Walker and Paddick2Walker R Paddick SM Dementia prevention in low-income and middle-income countries: a cautious step forward.Lancet Glob Health. 2019; 7: e538-e539Summary Full Text Full Text PDF PubMed Scopus (5) Google Scholar regarding the potentially overestimated number of dementia cases in the 10/66 dataset. We believe that the potential for dementia risk reduction through improving modifiable risk factors might be higher in LMICs because of the larger population of older adults and higher prevalence of risk factors. However, further research to clarify such discrepancies and more robust data from LMICs are needed so that estimates can be more accurate. 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 AccessPotential for dementia prevention in Latin America and Africa based on population-attributable fraction estimates – Authors' replyWe thank Deborah Oliveira and Cleusa Ferri for their interest in our Article on potentially modifiable risk factors in low-income and middle-income countries (LMICs).1 We agree that data from Africa is scarce in many such studies and welcome their study on population attributable fractions (PAF) in Portugal, Brazil, and Mozambique. In their Correspondence, Oliveira and Ferri comment on the discrepancy between our estimates of PAF in other Latin American countries and their lower estimate in Brazil. Full-Text PDF Open AccessPotential for dementia prevention in Latin America and Africa based on population-attributable fraction estimatesIn The Lancet Global Health, Mukadam and colleagues1 presented an important and useful analysis of data from India, China, and six Latin American countries in which they considered the population attributable fraction (PAF) for nine dementia risk factors.1 The risk factors they considered were low educational attainment, hearing loss, hypertension, obesity, smoking, depression, physical inactivity, social isolation, and diabetes. This study provides important evidence for putative intervention targets that could decrease the burden of dementia in low-income and middle-income countries (LMICs). Full-Text PDF Open Access