The effects of long-term cumulative HbA1c exposure on the development and onset time of dementia in the patients with type 2 diabetes mellitus: Hospital based retrospective study (2005–2021)

Aims We examined cumulative effects of long-term glycemic exposure in patients with type 2 diabetes mellitus (T2DM) on the development of dementia. Methods The study involved 20,487 records of patients with T2DM identified in the electronic medical record at Severance Hospital, Korea. Cumulative HbA1c (AUCHbA1c) and mean HbA1c over time (HbA1cavg) as measures of long-term glycemic exposure were compared for the development of dementia and the time to dementia. Results AUCHbA1c and HbA1cavg were significantly higher in patients who later developed dementia than in those who did not (AUCHbA1c: 56.2 ± 26.4 vs. 52.1 ± 26.1 %Year; HbA1cavg: 7.3 ± 1.0 vs. 7.0 ± 1.0%). Odds ratio of dementia increased when HbA1cavg was 7.2% (55 mmol/mol) or above, and when AUCHbA1c was 42 %Year (e.g., HbA1c 7.0% maintained for 6 years) or above. Among those who developed dementia, as HbA1cavg increased, the time to dementia onset decreased (β = -380.6 days, 95% confidence interval [CI]: −416.2 to −345.0). Conclusions Our results indicate poorly controlled T2DM was associated with an increased risk of developing dementia, as measured by AUCHbA1c and HbA1cavg. Higher cumulative glycemic exposure may lead to developing dementia in a shorter time.