Low Vitamin B12 and Brain Shrinkage
Methods: In 121 community-dwelling participants of the Chicago Health and Aging Project, serum markers of vitamin B12 status were related to summary measures of neuropsychological tests of 5 cognitive domains and brain MRI measures obtained on average 4.6 years later among 121 older adults.
Results: Concentrations of all vitamin B12–related markers, but not serum vitamin B12 itself, were associated with global cognitive function and with total brain volume. Methylmalonate levels were associated with poorer episodic memory and perceptual speed, and cystathionine and 2-methylcitrate with poorer episodic and semantic memory. Homocysteine concentrations were associated with decreased total brain volume. The homocysteine-global cognition effect was modified and no longer statistically significant with adjustment for white matter volume or cerebral infarcts. The methylmalonate-global cognition effect was modified and no longer significant with adjustment for total brain volume.
Conclusions: Methylmalonate, a specific marker of B12 deficiency, may affect cognition by reducing total brain volume whereas the effect of homocysteine (nonspecific to vitamin B12 deficiency) on cognitive performance may be mediated through increased white matter hyperintensity and cerebral infarcts. Vitamin B12 status may affect the brain through multiple mechanisms.
From press release:
Older people with low blood levels of vitamin B12 markers may be more likely to have lower brain volumes and have problems with their thinking skills, according to researchers at Rush University Medical Center.
The results of the study are published in the Sept. 27 issue of Neurology, the medical journal of the American Academy of Neurology.
Foods that come from animals, including fish, meat, especially liver, milk, eggs and poultry are usual sources of vitamin B12.
The study involved 121 older residents of the South side of Chicago who are a part of the Chicago Health and Aging Project (CHAP), which is a large, ongoing prospective Rush a biracial cohort of 10,000 subjects over the age of 65.
The 121 participants had blood drawn to measure levels of vitamin B12 and B12-related markers that can indicate a B12 deficiency. The same subjects took tests measuring their memory and other cognitive skills.
An average of four-and-a-half years later, MRI scans of the participants' brains were taken to measure total brain volume and look for other signs of brain damage.
Having high levels of four of five markers for vitamin B12 deficiency was associated with having lower scores on the cognitive tests and smaller total brain volume.
"Our findings definitely deserve further examination," said Christine C. Tangney, PhD, associate professor in the department of clinical nutrition at Rush University Medical Center, and lead author of the study. "It's too early to say whether increasing vitamin B12 levels in older people through diet or supplements could prevent these problems, but it is an interesting question to explore. Findings from a British trial with B vitamin supplementation are also supportive of these outcomes."
On the cognitive tests, the scores ranged from -2.18 to 1.42, with an average of 0.23. For each increase of one micromole per liter of homocysteine -- one of the markers of B12 deficiency -- the cognitive scores decreasedby 0.03 standardized units or points.
Tangney noted that the level of vitamin B12 itself in the blood was not associated with cognitive problems or loss in brain volume. She said that low vitamin B12 can be difficult to detect in older people when looking only at blood levels of the vitamin.
"Our findings lend support for the contention that poor vitamin B12 status is a potential risk factor for brain atrophy and may contribute to cognitive impairment," said Tangney.
C. C. Tangney, N. T. Aggarwal, H. Li, R. S. Wilson, C. DeCarli, D. A. Evans, M. C. Morris.
Vitamin B12, cognition, and brain MRI measures: A cross-sectional examination.
Department of Clinical Nutrition, Rush University Medical Center, Chicago, IL.