January 10, 2026
Low vitamin B12 status was associated with more rapid cognitive decline in a cohort followed over a 10-year period in Oxford, United Kingdom. Earlier studies have demonstrated a link between elevated concentrations of serum total homocysteine and Alzheimer disease. It was unclear whether this reflected inadequate vitamin B12 or folate status, or underlying vascular disease that may have contributed to the dementia. The aim of this study was to assess the longitudinal associations of cognitive decline with markers of vitamin B12 and folate status, to help answer that. The results of this study are published in the November 2007 issue of the American Journal of Clinical Nutrition.
The study population was part of a randomly selected cohort of older adults (65 + years) participating in the Oxford Healthy Aging Project. The rate of cognitive decline observed was more rapid in women than in men, in participants with higher systolic blood pressure and in those with the APOE ε4 allele. It did not appear to vary by level of education, smoking or history of vascular disease at enrollment. Two reliable markers of low vitamin B12 status, low serum concentrations of holoTC (the biologically active fraction of vitamin B12) and high MMA (a metabolic indicator of vitamin B12 function) were both independently and significantly associated with more rapid cognitive decline during a 10-year period. Folate status was not significantly associated with cognitive decline.
The results of this study suggest that differences in vitamin B12 status preceded the onset of cognitive decline. They further indicate that the variability in rates of cognitive decline is primarily explained by reduced vitamin B12 status. These findings may be relevant to older adults with cognitive impairment. The authors suggest that correction of vitamin B12 deficiency may be appropriate in those with relevant symptoms.
January is Alzheimer awareness month. Learn more about brain health and the Alzheimer Society’s national awareness campaign.
Read the abstract, Low vitamin B12 status and risk of cognitive decline in older adults.
Download Nutrition Perspective: Vitamin B12 and the Health of Canadians.
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