Table 1.
Observational study characteristics.
| Author/s | Population | Cognitive Measures | Dietary Measures | Sugar Type | Major Findings |
|---|---|---|---|---|---|
| Al-Sabah et al., 2020 a [44] | N = 1370 adolescents aged 11–16 | Raven’s Standard Progressive Matrices (SPM) | FFQ | Sugary drinks (frequency of consumption) |
Inverse relationship between sugary drink consumption and cognitive performance (p < 0.001). Sugary drink consumption a main predictor of cognitive function (p < 0.001). |
| Baym et al., 2014 a [40] | N = 52 children aged 7–9 | Memory tasks (paired associated images) | Youth–adolescent FFQ (YAQ) | Total sugar, added sugar (normalised by total daily kcal consumption) |
Total and added sugars had no relationship to memory. Performance impacted negatively by saturated fatty acids and positively by omega-3 fatty acids (ps < 0.05). |
| Berger et al., 2020 b [46] | N = 88 mother–infant pairs (mother M age = 68.1, SD = 6.7) | Bayley-III scales of infant development | FFQ at 1 and 6 months postnatal | Fructose, SSB (incl. juice), total sugar, added sugar (adjusted for kcal per day) |
Maternal fructose (p < 0.01) and SSB (p = 0.02) consumption at 1 month postnatal negatively associated with infant cognitive development at 24 months. Infant cognition lower in infants of obese mothers (p ≤ 0.001). No effect of maternal intake at 6 months. |
| Chong et al., 2019 a [14] | N = 1209 older adults aged 60 years and over (M = 68.1, SD = 5.6) | RAVLT, MMSE, MoCA, digit symbol (processing speed test, not described), VR |
Dietary history questionnaire (1 week recall) | Fructose, glucose, total sugar, added sugar, SSB, sugar from cakes and deserts, adjusted for daily calorie intake) |
Mild cognitive impairment had higher consumption of fructose (p = 0.004) and glucose (p = 0.032). MMSE scores lower in the higher percentile of total and free sugar intake (ps < 0.001). Risk of cognitive impairment increased 3.3-, 3.3-, and 3.6-fold in highest percentile of sucrose, total sugar, and free sugar, respectively (ps < 0.001). Risk of cognitive impairment increased by 3.7- and 1.8-fold for SSB and sugar from cakes and deserts, respectively (ps < 0.001). Reduction in risk of cognitive impairment by 35% in highest percentile of fruit consumption (p < 0.05). |
| Cohen et al., 2018 b [47] | N = 1234, mother–child pairs (tested during pregnancy and early childhood) | Peabody Picture Vocabulary Test (PPVT-III), WRAVMA, KBIT-II, WRAML |
FFQ | Maternal (prenatal) SSB consumption, child SSB consumption (not adjusted for energy intake) |
Maternal sucrose ingestion inversely associated with nonverbal KBIT-II (p = 0.03) and visual memory (p = 0.01) in mid-childhood. Maternal SSB ingestion inversely associated with nonverbal KBIT-II in mid-childhood (p = 0.03). Maternal diet soda consumption associated with lower WRAVMA in early childhood (p = 0.03) and verbal KBIT-II in mid-childhood (p < 0.001). Early childhood SSB consumption inversely associated with verbal KBIT-II in mid-childhood (p = 0.01). Fructose (p = 0.005) and fruit (p = 0.03) positively associated with PPVT-II in early childhood. |
| Gui et al., 2021 a [41] | N = 6387 children (3410 male) aged 6–12 (M = 8.6, SD = 1.5) | BRIEF | FFQ | HFCS from SSB (frequency of consumption) |
Associated with poor performance on executive function and high risk of executive dysfunction (ps < 0.0001). |
| Hassevoort et al., 2020 a [39] | N = 54 children (31 female) aged 8–12 (M = 9.1, SD = 0.8) | TTCT—Verbal form A | 3-day FFQ | Added sugar (normalised to intake per 1000 kcal) |
Inversely associated with fluency, originality, and overall TTCT score (p < 0.01). |
| Lester et al., 1982 a [38] | N = 184 children (100 male) aged 5–16 | WISC-R, WIPPSI, WRAT |
FFQ—24-h recall | Refined carbohydrates (adjusted for total calories) |
Negative relationship with all aspects of cognition (full-scale IQ (p = 0.001), performance IQ (p = 0.025), verbal IQ (p = 0.005), math (p = 0.005), and reading (p = 0.025)) other than spelling. Ratio of refined carbohydrates to total food calories negatively correlated with full-scale IQ (p < 0.015). |
| Naveed et al., 2020 a [43] | N = 487 children (250 male) aged 6–8 | Raven’s Coloured Progressive Matrices (RCPM) | FFQ | Fructose, sucrose, glucose (adjusted for daily energy intake) |
Increased fructose intake associated with higher fluid intelligence scores in all children (p = 0.002) and boys (p ≤ 0.001) but not girls alone; effect disappeared in all children and reduced in boys when fruits and berries were accounted for. No effect of glucose or sucrose |
| Øverby et al., 2013 a [45] | N = 482 students (236 male, M age = 14.6) | Self-reported schooling difficulties (maths, reading, and writing) | FFQ | SSB, junk food (frequency of consumption) |
Higher intake of SSB (p = 0.04) and junk food (p ≤ 0.001) associated with increased odds of self-reported math difficulties. Fruit intake associated with lower odds of math difficulties. No relationship with reading and writing difficulties. |
| Ye et al., 2011 c [48] | N = 737 adults aged 45–75 | MMSE, word list learning, digit span, clock drawing and figure copying (visual–spatial), STROOP, verbal fluency test |
FFQ (12-month estimate) | Total sugar, added sugar, SSB (adjusted for total energy intake) |
Increased sucrose (p = 0.014), glucose (p = 0.032), SSB (p = 0.005), and added fructose (p = 0.028), but not natural fructose, associated with lower MMSE. Total sugars inversely correlated with letter fluency (p < 0.05), recognition and recall (ps < 0.05), memory (p = 0.01), and MMSE (p = 0.02). Added sugars inversely associated with letter fluency (p < 0.05), long-term recall (p < 0.05), and MMSE (p = 0.005). |
| Zhang et al., 2022 a [42] | N = 1231 adolescents aged 13–18 (M = 15.77, SD = 1.7) | Modified Erikson flanker task, 1-back and 2-back tasks, more-odd shifting task |
FFQ | SSB (frequency of consumption) |
Drinking SSBs ≥2 times per week had worse performance for inhibition, working memory, and cognitive flexibility than no SSBs (ps < 0.001). |
Note: a = Cross-sectional study design; b = prospective cohort study design; c = retrospective cohort study; M = mean; FFQ = food frequency questionnaire; MMSE = Mini Mental State Exam; SSB = sugar-sweetened beverages; RAVLT = Rey Auditory Verbal Learning Memory Test; MoCA = Montreal Cognitive Assessment; VR = Visual Reproduction Test; WRAVMA = Wide-Range Assessment of Visual Motor Abilities; KBIT-II = Kaufman Brief Intelligence Test; WRAML = Wide-Range Assessment of Memory Learning; BRIEF = Parent-Rated Behavioural Rating Inventory of Executive Function; HFCS = high-fructose corn syrup; TTCT = Torrance Test of Creative Thinking; WISC-R = Wechsler Intelligence Scale for Children; WIPPSI = Wechsler Preschool and Primary Scale of Intelligence; WRAT = Wide-Range Achievement Test.