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Education and dementia in the context of the cognitive reserve hypothesis: a systematic review with meta-analyses and qualitative analyses.

Meng X, D'Arcy C - PLoS ONE (2012)

Bottom Line: The CR hypothesis postulates that CR reduces the prevalence and incidence of AD or VaD.Heterogeneity and sensitivity tests confirmed the evidence.Generally, study characteristics had no effect on conclusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. xim443@mail.usask.ca

ABSTRACT

Background: Cognitive reserve (CR) or brain reserve capacity explains why individuals with higher IQ, education, or occupational attainment have lower risks of developing dementia, Alzheimer's disease (AD) or vascular dementia (VaD). The CR hypothesis postulates that CR reduces the prevalence and incidence of AD or VaD. It also hypothesizes that among those who have greater initial cognitive reserve (in contrast to those with less reserve) greater brain pathology occurs before the clinical symptoms of disease becomes manifest. Thus clinical disease onset triggers a faster decline in cognition and function, and increased mortality among those with initial greater cognitive reserve. Disease progression follows distinctly separate pathological and clinical paths. With education as a proxy we use meta-analyses and qualitative analyses to review the evidence for the CR hypothesis.

Methodology/principal findings: We searched PubMed, PsycoINFO, EMBASE, HealthStar, and Scopus databases from January 1980 to June 2011 for observational studies with clear criteria for dementia, AD or VaD and education. One hundred and thirty-three articles with a variety of study designs met the inclusion criteria. Prevalence and incidence studies with odds ratios (ORs), relative risks or original data were included in the meta-analyses. Other studies were reviewed qualitatively. The studies covered 437,477 subjects. Prevalence and incidence studies with pooled ORs of 2.61 (95%CI 2.21-3.07) and 1.88 (95%CI 1.51-2.34) respectively, showed low education increased the risk of dementia. Heterogeneity and sensitivity tests confirmed the evidence. Generally, study characteristics had no effect on conclusions. Qualitative analyses also showed the protective effects of higher education on developing dementia and with clinical disease onset hastening a decline in cognition and function, and greater brain pathology.

Conclusion/significance: This systematic review and meta-analyses covering a wide range of observational studies and diverse settings provides robust support for the CR hypothesis. The CR hypothesis suggests several avenues for dementia prevention.

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Related in: MedlinePlus

Summary of findings from observational studies of education and the incidence of dementia (* denotes studies with two or more empirical findings).
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pone-0038268-g003: Summary of findings from observational studies of education and the incidence of dementia (* denotes studies with two or more empirical findings).

Mentions: Figure 3 shows the individual study and pooled estimates for incidence studies. The meta analysis used a random effects model, and results were unchanged using fixed effects model. The pooled OR for individuals with low education level compared to with high education was 1.88 (95%CI 1.51–2.34 p<0.001), indicating low education level were 0.88 times more likely to develop dementia than individuals with high levels of education. Heterogeneity here was significant (χ2 = 213.60, p<0.001). In these incidence studies the low/high education OR for AD was 1.82 (95%CI 1.36–2.44, p<0.001), heterogeneity was also significant (χ2 = 155.03, p<0.001). For VaD in these studies the low/high OR was 2.75 (95%CI 2.20–3.45, p<0.001) while heterogeneity was not significant (χ2 = 0.50, p = 0.78). The incidence OR for unspecified dementia was 1.48 (95%CI 1.17–.86, p<0.001), and the heterogeneity was not significant (χ2 = 4.70, p = 0.195).


Education and dementia in the context of the cognitive reserve hypothesis: a systematic review with meta-analyses and qualitative analyses.

Meng X, D'Arcy C - PLoS ONE (2012)

Summary of findings from observational studies of education and the incidence of dementia (* denotes studies with two or more empirical findings).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3366926&req=5

pone-0038268-g003: Summary of findings from observational studies of education and the incidence of dementia (* denotes studies with two or more empirical findings).
Mentions: Figure 3 shows the individual study and pooled estimates for incidence studies. The meta analysis used a random effects model, and results were unchanged using fixed effects model. The pooled OR for individuals with low education level compared to with high education was 1.88 (95%CI 1.51–2.34 p<0.001), indicating low education level were 0.88 times more likely to develop dementia than individuals with high levels of education. Heterogeneity here was significant (χ2 = 213.60, p<0.001). In these incidence studies the low/high education OR for AD was 1.82 (95%CI 1.36–2.44, p<0.001), heterogeneity was also significant (χ2 = 155.03, p<0.001). For VaD in these studies the low/high OR was 2.75 (95%CI 2.20–3.45, p<0.001) while heterogeneity was not significant (χ2 = 0.50, p = 0.78). The incidence OR for unspecified dementia was 1.48 (95%CI 1.17–.86, p<0.001), and the heterogeneity was not significant (χ2 = 4.70, p = 0.195).

Bottom Line: The CR hypothesis postulates that CR reduces the prevalence and incidence of AD or VaD.Heterogeneity and sensitivity tests confirmed the evidence.Generally, study characteristics had no effect on conclusions.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. xim443@mail.usask.ca

ABSTRACT

Background: Cognitive reserve (CR) or brain reserve capacity explains why individuals with higher IQ, education, or occupational attainment have lower risks of developing dementia, Alzheimer's disease (AD) or vascular dementia (VaD). The CR hypothesis postulates that CR reduces the prevalence and incidence of AD or VaD. It also hypothesizes that among those who have greater initial cognitive reserve (in contrast to those with less reserve) greater brain pathology occurs before the clinical symptoms of disease becomes manifest. Thus clinical disease onset triggers a faster decline in cognition and function, and increased mortality among those with initial greater cognitive reserve. Disease progression follows distinctly separate pathological and clinical paths. With education as a proxy we use meta-analyses and qualitative analyses to review the evidence for the CR hypothesis.

Methodology/principal findings: We searched PubMed, PsycoINFO, EMBASE, HealthStar, and Scopus databases from January 1980 to June 2011 for observational studies with clear criteria for dementia, AD or VaD and education. One hundred and thirty-three articles with a variety of study designs met the inclusion criteria. Prevalence and incidence studies with odds ratios (ORs), relative risks or original data were included in the meta-analyses. Other studies were reviewed qualitatively. The studies covered 437,477 subjects. Prevalence and incidence studies with pooled ORs of 2.61 (95%CI 2.21-3.07) and 1.88 (95%CI 1.51-2.34) respectively, showed low education increased the risk of dementia. Heterogeneity and sensitivity tests confirmed the evidence. Generally, study characteristics had no effect on conclusions. Qualitative analyses also showed the protective effects of higher education on developing dementia and with clinical disease onset hastening a decline in cognition and function, and greater brain pathology.

Conclusion/significance: This systematic review and meta-analyses covering a wide range of observational studies and diverse settings provides robust support for the CR hypothesis. The CR hypothesis suggests several avenues for dementia prevention.

Show MeSH
Related in: MedlinePlus