Metformin appears to be neuroprotective among older diabetic patients

  • Shi Q & al.
  • BMJ Open
  • 30 Jul 2019

  • International Clinical Digest
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Takeaway

  • Metformin (glucophage, others) use for ≥2 years is tied to lower risk for a composite outcome of 5 neurodegenerative diseases among older patients with type 2 diabetes mellitus (T2DM).

Why this matters

  • There is a lack of effective interventions for prevention, treatment.

Key results

  • Incidence of neurodegenerative diseases was 7.16% over a median 5.2-year follow-up.
  • Incidence rate per 1000 person-years:
    • 11.48 among metformin users.
    • 25.45 among metformin nonusers.
  • When nonusers were the comparator, risk was lower for patients using drug for:
    • 2-4 years (aHR=0.62; 95% CI, 0.45-0.85).
    • >4 years (aHR=0.19; 95% CI, 0.12-0.31).
  • No significant effect with use for ≤1 year or for 1-2 years.
  • Risk reductions greatest for dementia, Parkinson’s disease.

Study design

  • Retrospective cohort study among 5530 US veterans aged ≥50 years at the time of type 2 diabetes diagnosis who used insulin during at least two-thirds of follow-up, were initially free of neurodegenerative diseases, other mental disorders.
  • Propensity score weighting was applied to metformin use groups.
  • Main outcome: neurodegenerative diseases (dementia, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, mild cognitive impairment).
  • Funding: None.

Limitations

  • Lack of information on serum vitamin B12 level.
  • Limited ability to assess medication exposure, neurodegenerative disease outcomes.
  • Low incidence of some diseases.
  • Unclear generalisability.