Low vitamin C linked to cognitive impairment in older adults
A new report from the Alzheimer’s Association estimates 6.5 million Americans have Alzheimer’s disease, and more than 1 in 10 older adults have early stage memory or cognitive problems. The report revealed that 12-18% of adults over 60 have “mild cognitive impairment,” something that could be a precursor to dementia.
With cognitive impairment common among older populations, researchers from Flinders University set out to explore contributing factors. Their research found that cognitive impairment among older adults could be the result of low vitamin C levels. The research was published in the journal Antioxidants.
Vitamin C on the brain
Vitamin C accumulates in the central nervous system, with brain neurons containing especially high levels. Vitamin C also has a number of non-antioxidant functions, such as reducing metal (e.g. iron, copper) ions in the brain. Deficiency in vitamin C can lead to oxidative damage to macromolecules in the brain. While uncommon in developed countries, severe vitamin C deficiency, or scurvy, is a potentially fatal disease.
"Previous research has shown that vitamin C plays a significant role in the functioning of the brain, with studies finding that vitamin C deficiency may be associated with cognitive impairment, depression and confusion," explained lead author Yogesh Sharma, Associate Professor at Flinders University's College of Medicine and Public Health.
The researchers assessed the cognitive function and vitamin C levels of 160 patients aged 75 and older admitted to the Geriatric Evaluation and Management Unit at the Flinders Medical Center in Australia.
Cognitive status was determined by use of the Mini Mental State Examination (MMSE) and the Clock-Drawing Test (CDT). The MMSE is scored on a 30-point scale and uses items that assess: orientation (temporal and spatial, 10 points), memory (registration and recall, 6 points), attention and concentration, 5 points, language (verbal and written, 8 points), and visuospatial function (1 point).
The authors explained that they used CDT in addition to MMSE because studies indicate that the CDT is highly sensitive and specific in the detection of mild dementia and is reasonably accurate in separating patients with mild cognitive impairment (MCI) from healthy patients, and the combination of the CDT with the MMSE enhances the psychometric properties of these scales and is valid for detection of dementia.
The CDT was performed by providing the participants with a 10 cm pre-drawn circle on a piece of paper, and they were asked to draw an analogue clock, including all the numbers, and set the clock hands to a specified time of 10 past 11:00. Performance on the CDT depends upon a combination of visuospatial ability, executive function, motor function, attention, numerical knowledge and language comprehension Patients were scored on a simple subjective qualitative interpretation of clock drawing as normal (without error) and abnormal (with error).
Over half (57%) of the patients were found to have cognitive impairment, while 42 (26%) were found to be vitamin C deficient with a level below 11 micromol/L, below which point scurvy could develop.
"Our findings showed that cognitive function scores were significantly lower among patients who were vitamin C deficient, with further analysis suggesting vitamin C deficiency was almost three times more likely to be associated with cognitive impairment after adjustment for other factors," noted Sharma.
Scurvy symptoms throw curveball
The study also found that the symptoms associated with scurvy were present among patients with or without vitamin C deficiency. Many of these symptoms of vitamin C deficiency are common in older people, who may have bleeding, bruising and skin issues due to a number of other conditions.
Sharma said that as a result, it may be difficult to diagnose vitamin C deficiency solely on looking for these particular symptoms in older hospitalized patients.
"Given we know vitamin C deficiency is common among older hospitalized patients, medical professionals need to remain vigilant for this condition and confirm a patient's vitamin C status in suspected cases,” said Sharma.
This study indicates that vitamin C deficiency was associated with cognitive impairment as reflected by lower MMSE scores in vitamin C deficient patients when compared to those who were not vitamin C deficient. However, the authors acknowledged that the research doesn't prove that vitamin C is a direct cause of the cognitive impairment, but they could show that vitamin C deficiency is common and is associated with cognitive impairment in older hospitalized patients.
“Vitamin C deficiency is common, and there are few clinical correlates that can usefully lead to the identification of this condition in older hospitalized patients. Vitamin C deficiency is associated with cognitive impairment, and further studies are needed to confirm and characterize this association in greater detail,” the authors concluded.
"Relationship between Vitamin C Deficiency and Cognitive Impairment in Older Hospitalized Patients: A Cross-Sectional Study"
Authors: Y. Sharma et al.