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Vitamin D deficiency as a risk factor for dementia: a systematic review and meta-analysis.

Abstract

BACKGROUND

Sunlight exposure and high vitamin D status have been hypothesised to reduce the risk of developing dementia. The objective of our research was to determine whether lack of sunlight and hypovitaminosis D over time are associated with dementia.

METHODS

We systematically searched MEDLINE (via PubMed), Cochrane Library, EMBASE, SCOPUS, Web of Science, ICONDA, and reference lists of pertinent review articles from 1990 to October 2015. We conducted random effects meta-analyses of published and unpublished data to evaluate the influence of sunlight exposure or vitamin D as a surrogate marker on dementia risk.

RESULTS

We could not identify a single study investigating the association between sunlight exposure and dementia risk. Six cohort studies provided data on the effect of serum vitamin D concentration on dementia risk. A meta-analysis of five studies showed a higher risk for persons with serious vitamin D deficiency (<25 nmol/L or 7-28 nmol/L) compared to persons with sufficient vitamin D supply (≥50 nmol/L or 54-159 nmol/L) (point estimate 1.54; 95% CI 1.19-1.99, I2 = 20%). The strength of evidence that serious vitamin D deficiency increases the risk of developing dementia, however, is very low due to the observational nature of included studies and their lack of adjustment for residual or important confounders (e.g. ApoE ε4 genotype), as well as the indirect relationship between Vitamin D concentrations as a surrogate for sunlight exposure and dementia risk.

CONCLUSIONS

The results of this systematic review show that low vitamin D levels might contribute to the development of dementia. Further research examining the direct and indirect relationship between sunlight exposure and dementia risk is needed. Such research should involve large-scale cohort studies with homogeneous and repeated assessment of vitamin D concentrations or sunlight exposure and dementia outcomes.

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  • Authors+Show Affiliations

    ,

    Department for Evidence-based Medicine and Clinical Epidemiology, Danube University Krems, Dr.-Karl-Dorrek-Straβe 30, 3500, Krems, Austria. isolde.sommer@donau-uni.ac.at.

    ,

    Department for Evidence-based Medicine and Clinical Epidemiology, Danube University Krems, Dr.-Karl-Dorrek-Straβe 30, 3500, Krems, Austria. Cochrane Austria, Danube University Krems, Krems, Austria.

    ,

    Department for Evidence-based Medicine and Clinical Epidemiology, Danube University Krems, Dr.-Karl-Dorrek-Straβe 30, 3500, Krems, Austria. Cochrane Austria, Danube University Krems, Krems, Austria.

    ,

    Department for Clinical Neurosciences and Preventive Medicine, Danube University, Krems, Austria. MAS Alzheimerhilfe, Bad Ischl, Austria.

    ,

    Department for Evidence-based Medicine and Clinical Epidemiology, Danube University Krems, Dr.-Karl-Dorrek-Straβe 30, 3500, Krems, Austria. Cochrane Austria, Danube University Krems, Krems, Austria.

    ,

    Institute of Building Research & Innovation ZT-GmbH, Vienna, Austria.

    ,

    Institute of Building Research & Innovation ZT-GmbH, Vienna, Austria.

    Department for Evidence-based Medicine and Clinical Epidemiology, Danube University Krems, Dr.-Karl-Dorrek-Straβe 30, 3500, Krems, Austria. Cochrane Austria, Danube University Krems, Krems, Austria. RTI-UNC Evidence-based Practice Center, Research Triangle Institute International, North Carolina, USA.

    Source

    BMC geriatrics 17:1 2017 01 13 pg 16

    MeSH

    Cohort Studies
    Dementia
    Female
    Humans
    Risk Factors
    Sunlight
    Vitamin D
    Vitamin D Deficiency

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    28086755

    Citation

    Sommer, Isolde, et al. "Vitamin D Deficiency as a Risk Factor for Dementia: a Systematic Review and Meta-analysis." BMC Geriatrics, vol. 17, no. 1, 2017, p. 16.
    Sommer I, Griebler U, Kien C, et al. Vitamin D deficiency as a risk factor for dementia: a systematic review and meta-analysis. BMC Geriatr. 2017;17(1):16.
    Sommer, I., Griebler, U., Kien, C., Auer, S., Klerings, I., Hammer, R., ... Gartlehner, G. (2017). Vitamin D deficiency as a risk factor for dementia: a systematic review and meta-analysis. BMC Geriatrics, 17(1), p. 16. doi:10.1186/s12877-016-0405-0.
    Sommer I, et al. Vitamin D Deficiency as a Risk Factor for Dementia: a Systematic Review and Meta-analysis. BMC Geriatr. 2017 01 13;17(1):16. PubMed PMID: 28086755.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Vitamin D deficiency as a risk factor for dementia: a systematic review and meta-analysis. AU - Sommer,Isolde, AU - Griebler,Ursula, AU - Kien,Christina, AU - Auer,Stefanie, AU - Klerings,Irma, AU - Hammer,Renate, AU - Holzer,Peter, AU - Gartlehner,Gerald, Y1 - 2017/01/13/ PY - 2016/08/26/received PY - 2016/12/22/accepted PY - 2017/1/15/entrez PY - 2017/1/15/pubmed PY - 2017/6/14/medline KW - Dementia KW - Meta-analysis KW - Systematic review KW - Vitamin D SP - 16 EP - 16 JF - BMC geriatrics JO - BMC Geriatr VL - 17 IS - 1 N2 - BACKGROUND: Sunlight exposure and high vitamin D status have been hypothesised to reduce the risk of developing dementia. The objective of our research was to determine whether lack of sunlight and hypovitaminosis D over time are associated with dementia. METHODS: We systematically searched MEDLINE (via PubMed), Cochrane Library, EMBASE, SCOPUS, Web of Science, ICONDA, and reference lists of pertinent review articles from 1990 to October 2015. We conducted random effects meta-analyses of published and unpublished data to evaluate the influence of sunlight exposure or vitamin D as a surrogate marker on dementia risk. RESULTS: We could not identify a single study investigating the association between sunlight exposure and dementia risk. Six cohort studies provided data on the effect of serum vitamin D concentration on dementia risk. A meta-analysis of five studies showed a higher risk for persons with serious vitamin D deficiency (<25 nmol/L or 7-28 nmol/L) compared to persons with sufficient vitamin D supply (≥50 nmol/L or 54-159 nmol/L) (point estimate 1.54; 95% CI 1.19-1.99, I2 = 20%). The strength of evidence that serious vitamin D deficiency increases the risk of developing dementia, however, is very low due to the observational nature of included studies and their lack of adjustment for residual or important confounders (e.g. ApoE ε4 genotype), as well as the indirect relationship between Vitamin D concentrations as a surrogate for sunlight exposure and dementia risk. CONCLUSIONS: The results of this systematic review show that low vitamin D levels might contribute to the development of dementia. Further research examining the direct and indirect relationship between sunlight exposure and dementia risk is needed. Such research should involve large-scale cohort studies with homogeneous and repeated assessment of vitamin D concentrations or sunlight exposure and dementia outcomes. SN - 1471-2318 UR - https://www.unboundmedicine.com/medline/citation/28086755/Vitamin_D_deficiency_as_a_risk_factor_for_dementia:_a_systematic_review_and_meta_analysis_ L2 - https://bmcgeriatr.biomedcentral.com/articles/10.1186/s12877-016-0405-0 DB - PRIME DP - Unbound Medicine ER -