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

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 <1% below the age of 60 years to >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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  • Authors+Show Affiliations

    ,

    Laboratory of Epidemiology and Population Sciences, National Institute on Aging, NIA/NIH/IRP, 251 Bayview Blvd,, Suite 100, Room #: 04B118, Baltimore, MD 21224, USA. baydounm@mail.nih.gov.

    , , , ,

    Source

    BMC public health 14: 2014 Jun 24 pg 643

    MeSH

    Alcohol Drinking
    Alzheimer Disease
    Antioxidants
    Caffeine
    Cognition
    Cognition Disorders
    Dementia
    Diet
    Educational Status
    Exercise
    Fatty Acids, Omega-3
    Female
    Homocysteine
    Humans
    Male
    Smoking

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Research Support, N.I.H., Intramural
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    24962204

    Citation

    Beydoun, May A., et al. "Epidemiologic Studies of Modifiable Factors Associated With Cognition and Dementia: Systematic Review and Meta-analysis." BMC Public Health, vol. 14, 2014, p. 643.
    Beydoun MA, Beydoun HA, Gamaldo AA, et al. Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis. BMC Public Health. 2014;14:643.
    Beydoun, M. A., Beydoun, H. A., Gamaldo, A. A., Teel, A., Zonderman, A. B., & Wang, Y. (2014). Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis. BMC Public Health, 14, p. 643. doi:10.1186/1471-2458-14-643.
    Beydoun MA, et al. Epidemiologic Studies of Modifiable Factors Associated With Cognition and Dementia: Systematic Review and Meta-analysis. BMC Public Health. 2014 Jun 24;14:643. PubMed PMID: 24962204.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis. AU - Beydoun,May A, AU - Beydoun,Hind A, AU - Gamaldo,Alyssa A, AU - Teel,Alison, AU - Zonderman,Alan B, AU - Wang,Youfa, Y1 - 2014/06/24/ PY - 2013/09/11/received PY - 2014/05/13/accepted PY - 2014/6/26/entrez PY - 2014/6/26/pubmed PY - 2015/7/24/medline SP - 643 EP - 643 JF - BMC public health JO - BMC Public Health VL - 14 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 <1% below the age of 60 years to >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. SN - 1471-2458 UR - https://www.unboundmedicine.com/medline/citation/24962204/Epidemiologic_studies_of_modifiable_factors_associated_with_cognition_and_dementia:_systematic_review_and_meta_analysis_ L2 - https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-14-643 DB - PRIME DP - Unbound Medicine ER -