Metformin and Cognition in Older People

It’s been known for some time that the long-term use of metformin[1], one of the most common drugs used to treat diabetes, is associated with B-vitamin deficiencies[2]. Now a new study indicates[3] that metformin is also associated with worse cognitive function in older adults — and B-vitamin deficiency might be the reason.

The study, which was published in The Journal of Clinical Endocrinology and Metabolism[4], was led by Kirsty M. Porter, PhD, of Ulster University in Northern Ireland. The researchers, who wanted to explore the relationships between high blood sugar[5], B-vitamin status, and the use of metformin, studied over 4,000 older people (average age 74) who were taking part in the Trinity, Ulster and Department of Agriculture (TUDA) study.


The researchers divided the subjects into three groups: those whose blood sugar was normal, those who had high blood sugar and were taking metformin, and those who had high blood sugar and were not taking metformin. The researchers measured the subjects’ levels of folate, vitamin B12, and vitamin B6 and made cognitive assessments using two standard systems of measurement. “This is the first study,” Dr. Porter and colleagues pointed out[6], “to assess the impact of hyperglycemia and metformin on the biomarker status of all relevant B vitamins… and to investigate associations with cognitive health.”

The researchers determined that metformin use was associated with higher risks of deficiency of both vitamin B12 and vitamin B6. In addition, after adjusting for other possibilities, they reported that metformin use was also associated with an increased risk of cognitive dysfunction. Why might this be? The researchers inferred that “B vitamin deficiency may be implicated” in the cognitive decline.

The investigators also reported, however, that the consumption of vitamin-fortified foods help boost the vitamin B levels. According to Dr. Porter, “Fortified foods can provide a bioavailable source of B vitamins and may be beneficial for maintaining better cognitive health in older people with or at risk for diabetes,” but she added, “This requires confirmation in an intervention trial.”

Want to learn more about metformin? Read “What to Know About Metformin,”[7] “Diabetes Medicine: Metformin,”[8] and “Metformin: The Unauthorized Biography.”[9]

Joseph Gustaitis

A freelance writer and editor based in the Chicago area, Gustaitis has a degree in journalism from Columbia University.

  1. metformin:
  2. associated with B-vitamin deficiencies:
  3. a new study indicates:
  4. The Journal of Clinical Endocrinology and Metabolism:
  5. high blood sugar:
  6. pointed out:
  7. “What to Know About Metformin,”:
  8. “Diabetes Medicine: Metformin,”:
  9. “Metformin: The Unauthorized Biography.”:

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Joseph Gustaitis: Joseph Gustaitis is a freelance writer and editor based in the Chicago area. (Joseph Gustaitis is not a medical professional.)

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