Serum retinol levels are associated with cognitive function among community-dwelling older Mexican adults

ABSTRACT

Background

Vitamin A (VA) provides neuroprotection against oxidative stress and brain inflammation. VA deficiency (VAD) increases the risk of neurodegeneration in animal models, but results are inconclusive in humans: particularly in the older adult (OA) population which is at higher risk for micronutrient deficiencies and cognitive impairment.

Objective

To estimate the association between serum retinol levels and cognitive function (CF) in older Mexican adults.

Methods

Cross-sectional study with 803 adults aged ≥60 years with fasting blood sample from the southern region of Mexico, collected in summer of 2015. Low serum retinol (LSR) was defined if serum retinol ≤20 µg/dl. CF was evaluated using Semantic Verbal Fluency Test (SVFT). Mild cognitive impairment (MCI) was defined using normative values for SVFT. Linear and logistic regression models were used to estimate the association of LSR with CF and MCI, respectively.

Results

Prevalence of MCI was 9.35% and LSR 3.36%. OA with LSR evoked less words in the SVFT (β = −2.8, CI95% −4.6, −0.9) and had higher probability of MCI (OR =  2.7, CI95% 0.9, 7.7). Associations remained significant when considered IL-6.

Conclusion

Frequency of LSR in older Mexican adults was low, but strongly associated with MCI. This result suggests that VA plays a role in maintaining CF in the elderly population. Since VAD is a reversible condition, further studies are needed in order to identify the main causes of LSR and prevent MCI in populations which are at higher risk for malnutrition.

Trial registration: ClinicalTrials.gov identifier: NCT04820465.

KEYWORDS:

• Cognitive function
• mild cognitive impairment
• serum retinol
• semantic verbal fluency test

Acknowledgements

We would like to thank the older adults who participated in the study. Palazuelos-González Rosa Ángela drafted and wrote the manuscript with input from all authors, conducted the statistical analyses, and interpretation of data. De la Cruz-Góngora Vanessa was involved in the conception and design of the study, analysis, interpretation and discussion of data. Salinas-Rodríguez Aarón participated in the conception of the study, performed the statistical analysis and interpretation and discussion of data. All authors provided critical feedback, reviewed the entire manuscript and approved the final version of the manuscript.

Disclosure statement

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

Additional information

Funding

Funding for the original study was granted by the Consejo Nacional de Ciencia y Tecnología (CONACyT, by its Spanish acronym) with [grant number S0008-2014-1 – 000000000234157].

Notes on contributors

Rosa Palazuelos González

Rosa Palazuelos González studied nutrition in the Universidad Latinoamericana in Cuernavaca, Morelos Mexico, and the Master in Science in Population Nutrition at the School of Public Health of Mexico from the National Institute of Public Health in Cuernavaca, Morelos, Mexico. She works as a researcher at the Center for Research in Evaluation and Surveys (CIEE) of the National Institute of Public Health in the area of aging with topics related to geriatric syndromes such as sarcopenia, cognitive impairment, frailty, disability, and nutritional status. In addition, she is a university professor for an undergraduate program of nutrition.

Vanessa De la Cruz-Góngora

Vanessa De La Cruz-Góngora, Mexican. Graduated in License in Nutrition, University of Veracruz; Master in Sciences in Nutrition and Doctorate in Science in Population Nutrition at the School of Public Health of Mexico (SPHM) in the National Institute of Public Health (NIPH), Mexico. Over the last 15 years, I have been working at the National Institute of Public Health. My current adscription is at the Center of Evaluation and Survey Research, NIPH. Scientific Researcher recognized by the National Research System (Level 1), and the Commission for National Institutes of Health in Mexico (Researcher in Medical Sciences level “D”). Member of the actual Ethic Research Committee in the NIPH. Professor of “nutrition and aging” course in the Master and Doctorate on Sciences in Nutrition program of the SPHM. Author/co-author of 33 peer reviewed scientific articles and 5 chapters book. In 2019, I was granted with the prestigious “Young Researcher Award” in Public Health at the NIPH. My research interests is on nutrition in population, focus on the epidemiology of micronutrient deficiencies and anemia; iron absorption and metabolism; nutrition and aging; nutrition and cognitive function in older adults;and the burden of chronic disease in populations (diabetes and stroke).

Aarón Salinas Rodríguez

Aarón Salinas Rodríguez, Master of Science in Biostatistics. Researcher in Medical Sciences at the National Institute of Public Health. He is a professor at the Mexican School of PublicHealth in courses on biostatistics, categorical data, and longitudinal data. He has published scientific articles in the areas of aging, statistics, and program evaluation in international journals. His research interests include statistical methodology and studies on population aging. He is a member of the National System of Researchers in Mexico, the Mexican Association of Statistics, and the Latin American Thematic Network on Aging.