Potential for dementia prevention in Latin America and Africa based on population-attributable fraction estimates
Authors: Joshua R Ehrlich, Kenneth M Langa
Journal: The Lancet Global Health (2019)

In The Lancet Global Health, 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 (87) Google Scholar 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.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 (87) Google Scholar 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). The authors chose the risk factors for their study on the basis of previous comprehensive literature reviews, but other important modifiable risk factors in LMICs might have been overlooked. For instance, there is mounting evidence for an association between vision loss and dementia, including in several of the countries in this study. In one study of older adults from several LMICs, poor distance vision was associated with worse memory in China, Ghana, India, and Mexico after adjusting for age and socioeconomic status.2Ehrlich JR Stagg BC Andrews C Kumagai A Musch DC vision impairment and receipt of eye care among older adults in low- and middle-income countries.JAMA Ophthalmol. 2018; (published online Nov 21.)DOI:10.1001/jamaophthalmol.2018.5449Google Scholar In a study from China in which more than 250 000 older adults underwent full psychiatric, vision, and hearing examinations, the prevalence of dementia was highest among those with dual-sensory impairment (1·27%), followed by vision (0·83%) and hearing (0·61%) impairments.3Luo Y He P Guo C Chen G Li N Zheng X Association between sensory impairment and dementia in older adults: evidence from China.J Am Geriatr Soc. 2018; 66: 480-486Crossref PubMed Scopus (31) Google Scholar A population-based study from the USA showed that over 9 years, vision impairment was associated with greater declines in Modified Mini-Mental State Examination scores and with a higher risk of incident cognitive impairment.4Swenor BK Simonsick EM Ferrucci L et al.Visual impairment and incident mobility limitations: the health, aging and body composition study.J Am Geriatr Soc. 2015; 63: 46-54Crossref PubMed Scopus (42) Google Scholar Approximately 75% of vision impairment and blindness is preventable or curable, and 90% of affected individuals live in LMICs.5Bourne RRA Stevens GA White RA et al.Causes of vision loss worldwide, 1990–2010: a systematic analysis.Lancet Glob Health. 2013; 1: e339-e349Summary Full Text Full Text PDF PubMed Scopus (921) Google Scholar Additionally, more than half of the global burden of blindness and vision impairment is due to cataract and refractive error,5Bourne RRA Stevens GA White RA et al.Causes of vision loss worldwide, 1990–2010: a systematic analysis.Lancet Glob Health. 2013; 1: e339-e349Summary Full Text Full Text PDF PubMed Scopus (921) Google Scholar both of which can be cured through quick low-cost interventions. Accordingly, it will be important to identify the proportion of dementia cases that are theoretically preventable by improving vision, because this might represent a relatively accessible intervention target to slow the growing burden of dementia in LMICs. 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 estimatesWe read with interest the study by Mukadam and colleagues1 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,2 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. 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 Access