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Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis.
BMC Public Health. 2014 Jun 24; 14:643.BP

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.

Links

PMC Free PDF

Authors+Show Affiliations

Beydoun MA
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.
Beydoun HA
No affiliation info available
Gamaldo AA
No affiliation info available
Teel A
No affiliation info available
Zonderman AB
No affiliation info available
Wang Y
No affiliation info available

MeSH

Alcohol DrinkingAlzheimer DiseaseAntioxidantsCaffeineCognitionCognition DisordersDementiaDietEducational StatusExerciseFatty Acids, Omega-3FemaleHomocysteineHumansMaleSmoking

Pub Type(s)

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

Language

eng

PubMed ID

24962204

Clinical Trial Links

Serum, Dietary and Supplemental Vitamin D's Association With Cognitive Decline

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, 643. https://doi.org/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/full_citation DB - PRIME DP - Unbound Medicine ER -