Metformin in diabetesmellitus, causes reduced vitaminB12-absorption. Prolonged B12deficiency causes neuronal injury which with diabetic microangiopathic ischemic-vascular injury sets the stage for dementia.
Survey PREVALENCE /DEGREE of LOW totalserumB12 in Diabetics on long-term metformin in GeylangPolyclinic.
Conducted from mid2018 to mid2020, involving 365patients,
98% at routine chronic review, 2% during pre-teleconsult scrubbing, randomised by clinic-appointment/walk-in system.
CRITERIA FOR INCLUSION–>patients on metformin>500mg Bd minimum 2yrs. SerumB12 levels ordered after consultation/scrubbing were later traced. If on B12supplement, year supplement started, B12level, age, metformin dose/duration at that time noted.
FORTHIS STUDY, CUT-OFFPOINT for LOW B12/B12 DEFICIENCY WAS TAKEN AS <130PMOL/L
N=365; 139PTS/365 (38%) HAD B12<130PMOL/L –>23% on metformin 500mg Bd/tds, 73% on 850mg BD/more. METFORMIN TAKEN 5–>15yrs in 75%; <5 yrs in 25%.
19PTS HAD TOTALSerumB12<60PMOL/L; MEAN age 68yrs, MEAN B12level 50.8pmol/L. MEAN/MEDIAN duration of metformin 7.7/7yrs; 3/19 pts were in their 13th,13th,15th metformin-yr. 120PTS HAD B12levels 61pmol/L –129PMOL/L; MEAN age 65.9yrs, MEAN B12level->101pmol/L, 45% aged 60->69 yrs. MEAN/MEDIAN duration of metformin was 8 yrs/8 yrs. MODE 10yrs.
POST-STARTING METFORMIN>500mgBD –>LowB12 found within 1yr in 5 patients; 41% found within6 yrs; remaining 59% from7th–15thyr of treatment.
IF PATIENT HAD LOW B12<130PMOL/L AFTER 1YR METFORMIN RX &THIS WAS ONLY DETECTED IN THE 15THyr of metformin (taking both extremes found), patient would have been B12deficient for 15yrs. Would this be sufficient to set the stage for irreversible neuronal injury/dementia?
From existing studies, once dementia is diagnosed, highdoseB12 supplements do not slow cognitive decline. B12level should be checked every2–>3yrs after starting>500mg bd metformin, especially in 60->69yrolds, for dementia risk reduction.