Association of vitamin A and its organic compounds with stroke – a systematic review and meta-analysis

ABSTRACT

Purpose

The main purpose of this systematic review was to evaluate the association between the stroke (risk of stroke and the mortality due to stroke) and vitamin A, its organic compounds and its provitamins.

Method

Major databases including PubMed, Scopus, and Web of Science were searched. Studies with human samples were included for risk assessment. The association was assessed using odds ratio (log(OR)) and a random-effect model. I² statistic, variance (tau²) and prediction interval were used for heterogeneity assessment. The funnel plot was used for publication bias.

Results

Twenty-one studies including 5789 stroke patients were retrieved. Twenty studies had sufficient information for quantitative analyses. The pooled effect showed an inverse association between vitamin A and its organic compound with the risk of stroke (log(OR) = −0.46 95%CI (−0.81;−0.12)) and with the risk of mortality due to stroke (log(OR) = −0.39 95%CI (−0.74;−0.04)). However, according to subgroup analyses, the association was dependent on the compound in a way that retinol and beta-carotene were the most effective compounds. The effects of several confounding factors and the threshold levels for vitamin A and its organic compound on the effectiveness were discussed.

Conclusion

Insufficiency of retinol and beta-carotene significantly increased the risk of stroke; however, due to heterogeneity between studies more studies are needed for evaluating clinical significance of this outcome.

KEYWORDS:

• Vitamin A
• retinol
• retinoic acid
• carotenes
• stroke
• systematic review

Acknowledgements

All authors contributed equally to the study design. S.F and S.S performed the systematic search, title, abstract and full-text screening steps. S.F performed statistical and meta-analyses and wrote the initial draft. All authors contributed equally for discussing the results and revising the draft.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Authors would like to thank the Deputy of Research and Technology, Hamadan University of Medical Sciences, for its support for the study [IR.UMSHA.REC.1400.924/grant number 1400120310145].

Notes on contributors

Sajjad Farashi

Sajjad Farashi is with Autism Spectrum Disorders Research Center, Hamadan University of Medical Sciences and working mainly on topics related to stroke in human focusing on neurophysiological markers.

Siamak Shahidi

Siamak Shahidi is with the neurophysiology research center, Hamadan University of Medical Sciences and working mainly on topics related to stroke, learning and memory, and neurologic disorders in human or animal species.

Abdolrahman Sarihi

Abdolrahman Sarihi is with the neurophysiology research center, Hamadan University of Medical Sciences and working mainly on topics related to stroke, learning and memory, and physiological mechanisms in human or animal species.

Mohammad Zarei

Mohammad Zarei is with the neurophysiology research center, Hamadan University of Medical Sciences and working mainly on topics related to the effect of chemical agents on the neurologic disorders in human or animal species.