Habitual sugar intake and cognitive impairment among multi-ethnic Malaysian older adults
CP Chong,1S Shahar,1H Haron,1 and N Che Din2Author informationArticle notesCopyright and License informationDisclaimerCopyright © 2019 Chong et al.This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php).This article has been cited by other articles in PMC.Go to:
Background: Sugar is widely consumed in Malaysia, and the excessive intake of sugar has been associated with cognitive functions. However, the association between sugar intake and cognitive impairment among Malaysian older adults is yet to be determined.
Purpose: The objective of this study was to evaluate the associations between types and sources of sugar intake and cognitive functions and to identify their risk in predicting cognitive impairment (MMSE score <24).
Subjects and methods: A total of 1,209 subjects aged ≥60 years were recruited through multi-stage random sampling from selected states in Malaysia. Dietary intake was derived using a 7-day dietary history questionnaire and supplemented with a quantitative food frequency questionnaire for added sugar intake.
Results: The prevalence of cognitive impairment as defined by Mini-Mental State Examination (MMSE) less than 24 was 31.9%, while the prevalence of mild cognitive impairment was 13.1%. The median (IQR) for total sugar intake was 44.60 g/day (26.21–68.81) or 8 tsp, and free sugar intake was 33.08 g/day (17.48–57.26) or 6 tsp. The higher intake of total sugars, free sugars, sucrose, lactose, sugar-sweetened beverages, sugar-sweetened cakes, and dessert was found to be significantly associated with a lower MMSE score, after adjusting for covariates. On the other hand, the consumption of cooked dishes and fruits was significantly associated with a better MMSE score. The adjusted OR for risk of cognitive impairment (MMSE score <24) was 3.30 (95% CI 2.15–5.08) for total sugars and 3.58 (95% CI 2.32–5.52) for free sugars, comparing the highest with the lowest intake percentiles.
Conclusion: Excessive sugar consumption among older adults showed a notable association with poor cognitive functions, but longitudinal studies and clinical trials are further needed to clarify the direction of causality and to investigate the underlying mechanism.Keywords: sugar intake, free sugar, sucrose, cognitive functions, older adultsGo to:
Sugar, in the form of glucose, is the primary energy source for cognitive functions. However, excessive sugar consumption may lead to impaired memory, and link to an increased risk of dementia.1 WHO (2015) recommended “free sugar” intake of 25 g per day for an adult of normal BMI and the Malaysia dietary recommendation suggested intake of <10% of the total calories from total sugar.2 Nevertheless, the Food Balance Sheets showed that the amount of available sugar (kg per capita per year) has risen by 91% from 22.51 kg in 1963 to 42.96 kg in 2013. At this level, Malaysia ranks among the topmost countries in Asia concerning the availability of sugar.3 This dietary pattern that involves the rapid escalation of the availability of sugar is quite alarming, as it is related to an increase in the prevalence of obesity and type 2 diabetes.4,5
Sugar intake has also been linked with high blood glucose,4 high blood pressure,6 dyslipidemia,7 and a constellation of these metabolic risk factors, ie, the metabolic syndrome.8 Metabolic syndrome has been linked with cognitive impairment and type 2 diabetes is also considered to be a significant risk factor for impaired cognitive function. However, the effect of sugar consumption on cognitive health continues to be a controversial topic.
Data from animal studies have suggested that sugar intake might play a role in cognitive impairment. Studies have examined the effect of sugary diets on spatial learning and memory in the Morris Water Maze found that feeding rats with sugar solution (notable sucrose) showed impaired spatial learning and memory,9–12 while fructose-fed rats showed poorer long-term spatial memory with peripheral metabolic dysfunction (elevated serum glucose, insulin, and triglycerides).13 Accordingly, the results from animal studies provide strong evidence that sugar impairs spatial memory via damage to the hippocampus, a region known to be integral to spatial learning and memory.14
The limited human studies investigating high sugar intake also concurred that sugar consumption could have a significant impact on one’s cognitive abilities. A population-based study among Puerto-Ricans aged between 45 and 75 years old found that total sugars, added sugars, sucrose, glucose, added fructose, and sugar-sweetened beverages were each significantly inversely associated with cognitive function as assessed using Mini-Mental State Examination (MMSE).15 Additionally, in a dietary pattern study, Gustaw–Rothenberg investigated the dietary pattern of Alzheimer’s disease (AD) patients characterized as having a high intake of meat, butter, high-fat dairy products, eggs, and refined sugar as compared to the control.16 Similarly, Power et al, in a community-dwelling of an elderly Irish cohort found that the consumption of a high glycaemic diet was associated with impaired cognitive performance as assessed by the MMSE.17 Recently, a double-blind, placebo-controlled, cross-over experimental study was undertaken suggesting that the ingestion of glucose and sucrose led to lower performance of cognitive tasks, ie, simple response time, arithmetic, and Stroop interference.18 Most studies used a single test to determine the cognitive functions. Thus, the present study was conducted to determine the association between sugar intake and cognitive functions as measured by a series of cognitive tests ie digit span, Rey’s auditory verbal learning test (RAVLT), MMSE, Montreal Cognitive Assessment (MoCA), digit symbol, and visual-reproduction test (VR) among multi-ethnic Malaysian older adults.