A meta-analysis of peripheral tocopherol levels in age-related cognitive decline and Alzheimer’s disease

ABSTRACT

Objectives: Findings from observational studies and clinical trials on the associations between vitamin E and dementia remain controversial. Here we conducted a meta-analysis to determine the difference in blood tocopherols levels between patients with Alzheimer's disease (AD) or age-related poor cognitive function and healthy controls.

Methods: Standardised mean difference (SMD) and 95% confidence intervals (CIs) were calculated and entered into a random effects model. Study quality, heterogeneity and publication bias were also investigated.

Results: Thirty-one articles were included in the meta-analysis, which included analyses for α-, β-, γ- and δ-tocopherols. These results indicated that individuals with AD or age-related cognitive deficits and mild cognitive impairment (MCI) had lower circulatory concentrations of α-tocophenol compared with healthy controls (AD: SMD = −0.97, 95% confidence interval [CI] = −1.27 to −0.68, Z = 6.45, P < 0.00001; age-related cognitive deficits and MCI: SMD = −0.72, 95% CI = −1.12 to −0.32, Z = −3., P < 0.0005). Levels of β-, γ- and δ-tocophenols did not significantly differ between groups of AD and age-related cognitive deficits compared to controls.

Discussion: These results suggest that lower α-tocopherol levels have a strong association with AD and MCI supporting evidence for the role of diet and vitamin E in AD risk and age-related cognitive decline.

KEYWORDS:

• Vitamin E
• α-tocopherol
• γ-tocopherol
• Alzheimer's disease
• MCI
• diet
• meta-analysis

Acknowledgements

SA, SB and CM designed the study. SA and CM performed the literature searches and data extraction. All authors contributed to the final version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Stephanie Ashley

Stephanie Ashley is a third-year undergraduate student at Manchester Metropolitan University. This study was her undergraduate research project.

Steven Bradburn

Steven Bradburn is a postdoctoral student at Manchester Metropolitan University. He gained his Ph.D. from Manchester Metropolitan University.

Chris Murgatroyd

Chris Murgatroyd is a reader in molecular neuroscience at Manchester Metropolitan University. He gained his Ph.D. from the Ludwig Maximillian University, Munich.