Epidemiologic studies of modifiable factors associated with cognition and dementia: Systematic review and meta-analysis

May A. Beydoun, Hind A. Beydoun, Alyssa A. Gamaldo, Alison Teel, Alan B. Zonderman, Youfa Wang

Research output: Contribution to journalArticle

Abstract

Background: Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer's disease (AD) is the most frequent cause of dementia, increasing in prevalence from 40% above 85 years of age. Methods. We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias. Results: In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ∼38.9% for caffeine to ∼89% for physical activity. Education also had a significantly higher propensity for "a positive finding" compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found. Conclusions: Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

Original languageEnglish (US)
Article number643
JournalBMC Public Health
Volume14
Issue number1
DOIs
StatePublished - Jun 24 2014

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Cognition
Dementia
Meta-Analysis
Epidemiologic Studies
Alzheimer Disease
Caffeine
Odds Ratio
Homocysteine
Smoking
Publication Bias
Population
Omega-3 Fatty Acids
Education
Antioxidants
Health
MEDLINE
Sample Size
Cohort Studies
Cross-Sectional Studies
Alcohols

Keywords

  • Alzheimer's disease
  • Cognition
  • Dementia
  • Meta-analysis
  • Nutrition
  • Risk factor

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Medicine(all)

Cite this

Epidemiologic studies of modifiable factors associated with cognition and dementia : Systematic review and meta-analysis. / Beydoun, May A.; Beydoun, Hind A.; Gamaldo, Alyssa A.; Teel, Alison; Zonderman, Alan B.; Wang, Youfa.

In: BMC Public Health, Vol. 14, No. 1, 643, 24.06.2014.

Research output: Contribution to journalArticle

Beydoun, May A. ; Beydoun, Hind A. ; Gamaldo, Alyssa A. ; Teel, Alison ; Zonderman, Alan B. ; Wang, Youfa. / Epidemiologic studies of modifiable factors associated with cognition and dementia : Systematic review and meta-analysis. In: BMC Public Health. 2014 ; Vol. 14, No. 1.
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AU - Beydoun, May A.

AU - Beydoun, Hind A.

AU - Gamaldo, Alyssa A.

AU - Teel, Alison

AU - Zonderman, Alan B.

AU - Wang, Youfa

PY - 2014/6/24

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N2 - Background: Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer's disease (AD) is the most frequent cause of dementia, increasing in prevalence from 40% above 85 years of age. Methods. We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias. Results: In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ∼38.9% for caffeine to ∼89% for physical activity. Education also had a significantly higher propensity for "a positive finding" compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found. Conclusions: Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

AB - Background: Cognitive impairment, including dementia, is a major health concern with the increasing aging population. Preventive measures to delay cognitive decline are of utmost importance. Alzheimer's disease (AD) is the most frequent cause of dementia, increasing in prevalence from 40% above 85 years of age. Methods. We systematically reviewed selected modifiable factors such as education, smoking, alcohol, physical activity, caffeine, antioxidants, homocysteine (Hcy), n-3 fatty acids that were studied in relation to various cognitive health outcomes, including incident AD. We searched MEDLINE for published literature (January 1990 through October 2012), including cross-sectional and cohort studies (sample sizes > 300). Analyses compared study finding consistency across factors, study designs and study-level characteristics. Selecting studies of incident AD, our meta-analysis estimated pooled risk ratios (RR), population attributable risk percent (PAR%) and assessed publication bias. Results: In total, 247 studies were retrieved for systematic review. Consistency analysis for each risk factor suggested positive findings ranging from ∼38.9% for caffeine to ∼89% for physical activity. Education also had a significantly higher propensity for "a positive finding" compared to caffeine, smoking and antioxidant-related studies. Meta-analysis of 31 studies with incident AD yielded pooled RR for low education (RR = 1.99; 95% CI: 1.30-3.04), high Hcy (RR = 1.93; 95% CI: 1.50-2.49), and current/ever smoking status (RR = 1.37; 95% CI: 1.23-1.52) while indicating protective effects of higher physical activity and n-3 fatty acids. Estimated PAR% were particularly high for physical activity (PAR% = 31.9; 95% CI: 22.7-41.2) and smoking (PAR%=31.09%; 95% CI: 17.9-44.3). Overall, no significant publication bias was found. Conclusions: Higher Hcy levels, lower educational attainment, and decreased physical activity were particularly strong predictors of incident AD. Further studies are needed to support other potential modifiable protective factors, such as caffeine.

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