Higher Dementia Incidence in Older Adults With Type 2 Diabetes and Large Reduction in HbA1c

Allen T.C. Lee; Marcus Richards; Wai C. Chan; Helen F.K. Chiu; Ruby S.Y. Lee; Linda C.W. Lam


Age Ageing. 2019;48(6):838-844. 

In This Article

Abstract and Introduction


Background: although type 2 diabetes increases risk of dementia by 2-fold, whether optimizing glycemic level in late life can reduce risk of dementia remains uncertain. We examined if achieving the glycemic goal recommended by the American Diabetes Association (ADA) within a year was associated with lower risk of dementia in 6 years.

Methods: in this population-based observational study, we examined 2246 community-living dementia-free Chinese older adults with type 2 diabetes who attended the Elderly Health Centres in Hong Kong at baseline and followed their HbA1c level and cognitive status for 6 years. In line with the ADA recommendation, we defined the glycemic goal as HbA1c < 7.5%. The study outcome was incident dementia in 6 years, diagnosed according to the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10) or Clinical Dementia Rating of 1–3.

Results: those with HbA1c ≥ 7.5% at baseline and HbA1c < 7.5% in 1 year were associated with higher rather than lower incidence of dementia, independent of severe hypoglycemia, glycemic variability and other health factors. Sensitivity analyses showed that a relative reduction of ≥10%, but not 5–10%, in HbA1c within a year was associated with higher incidence of dementia in those with high (≥8%) and moderate (6.5–7.9%) HbA1c at baseline.

Conclusion: a large reduction in HbA1c could be a potential predictor and possibly a risk factor for dementia in older adults with type 2 diabetes. Our findings suggest that optimizing or intensifying glycemic control in this population requires caution.


Dementia is a global health problem. Dementia prevention is particularly important to people with type 2 diabetes because their number is growing,[1] and they are twice as likely to develop dementia as those without.[2] One possible mechanism underlying higher dementia risk in diabetes is hyperglycemia.[2–4] While higher HbA1c is associated with higher dementia risk,[5–8] it is unclear whether improving glycemic control could reduce the risk. With evidence suggesting that intensive glycemic lowering might paradoxically elevate risks of morbidities and mortality,[9–11] studies that examine optimizing glycemic level and the associated risk of dementia are much needed.

In this study, we followed the glycemic level and cognitive status of community-living dementia-free older adults with type 2 diabetes and examined the association of glycemic changes in 1 year with risk of dementia in 6 years. We hypothesized that maintaining HbA1c above the glycemic target recommended by the American Diabetes Association (ADA) was associated with higher dementia risk, whereas achieving the target within a year was associated with lower risk. Our findings might support and extend the previous literature that hyperglycemia is important to the development of dementia, and optimizing glycemic level, even in late life, can help prevent dementia.