Correlation between Plasma Vitamin C Levels and Cognition: A Cross-Sectional Study

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Low plasma vitamin C and E have been more likely to be found in demented patients than in healthy controls. This is supported by findings from a prospective cohort study from Department of Health/Medical Research Council Nutritional Programme in which participants (n = 921; greater than or equal to 65 years) with the lowest Vitamin C status displayed the poorest cognitive function, a finding which persisted when corrected for age, illness, social class, or other dietary variables. Additionally, a recent an epidemiological prospective cohort study showed that high dietary intake of vitamin C and vitamin E may lower the risk of Alzheimer disease. Higher vitamin C blood levels have been found in association with a better memory performance among subjects older than 65 years. Studies have shown that blood vitamin C concentration falls during acute phase responses such as after surgery, trauma, sepsis, and burns. Researchers at the University of Toronto have shown that anaesthetics following surgery can cause long-term memory loss. In a recent study, blood concentration of vitamin C decreased post-operatively and the reduction was significant 7 days after coronary heart surgery. A study is yet to correlate paper and pen assessments such as the Mini mental State Examination (MMSE), Hopkins Verbal Learning test (HVLT-R) and symbol digit modalities test (SDMT) with a computer based cognitive testing such as the SUCCAB. The SUCCAB assesses accuracy and speed, which have been shown to correlate to cognitive decline through ageing. There is consensus that crystallised abilities (vocabulary and general knowledge) can remain stable until very late in life whereas fluid abilities (attention, executive function and memory) decline from middle adulthood until late age. The cognitive tests incorporated in the present study will primarily examine these fluid abilities. The MMSE assesses cognitive impairments in clinical and research settings. The HVLT-R is a reliable neuropsychological test of many aspects of verbal learning and memory, requiring subjects to recall as many items as possible from a list of common words. The SDMT measures the time to pair abstract symbols with specific numbers. The test requires elements of attention, visuoperceptual processing, working memory, and psychomotor speed. Previous research measuring vitamin C has incorporated simple food questionnaires to predict vitamin C levels. The proposed study will measure serum vitamin C levels thoroughly through a means of ELISA testing. The proposed project aims to examine vitamin C serum concentration and cognitive performance measured by SUCCAB, and the pen and paper tests, including the MMSE, SDMT, and HVLT-R.