Latest research published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) shows an association between type 2 diabetes (T2D) and developing dementia in later life – with the chance of dementia increasing the sooner an individual develops T2D. The study is by PhD student Jiaqi Hu and Professor Elizabeth Selvin of the Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA, and colleagues.
Their study investigated the association between prediabetes and dementia. Prediabetes is an intermediate stage of high blood sugar, where blood sugar is high but has not yet crossed the edge for T2D. Prediabetes confers a high risk of progression to diabetes but can be independently related to other clinical outcomes. Most individuals who develop T2D first go through this ‘window’ of prediabetes.
The danger of progression to T2D amongst individuals with prediabetes is substantial; amongst middle-aged adults with prediabetes, 5–10% per yr go on to develop T2D, with total of 70% of those with prediabetes progressing to T2D during their lifetime. Within the USA, as much as 96 million adults have prediabetes, accounting for 38% of the adult population.
To know the risks of dementia related to prediabetes, the authors analysed data from participants of the Atherosclerosis Risk in Communities (ARIC) study. Those enrolled were aged 45–64 years in 1987–1989 and from 4 US counties: Forsyth County, North Carolina; Jackson, Mississippi; suburbs of Minneapolis, Minnesota; and Washington County, Maryland. The baseline period for the evaluation was visit 2 of the study (1990–1992), which was the primary time where HbA1c (glycated haemoglobin – a measure of blood sugar control) and cognitive function were measured on this study.
The cognitive function assessments incorporated data from a scoring system involving three cognitive tests, administered at visits 2 (1990–1992) and 4 (1996–1998), the expanded neuropsychological ten-test collection, administered from visit 5 (2011–2013) onwards and informant interview (Clinical Dementia Rating [CDR] scale and the Functional Activities Questionnaire [FAQ]). The Mini-Mental State Examination (MMSE) was also administered. Participants were followed up until 2019.
The authors defined prediabetes as glycated haemoglobin (HbA1c – a measure of blood sugar control) of 39–46 mmol/mol (5.7–6.4%). Additionally they checked out subsequent diagnoses of T2D during follow-up.
The authors evaluated the association of prediabetes with dementia risk before and after accounting for the following development of T2D amongst ARIC participants with prediabetes at baseline. This was done to know how much of the association of prediabetes with dementia was explained by progression to diabetes. Additionally they evaluated whether age at diabetes diagnosis modified the chance of dementia.
Amongst 11,656 participants without diabetes at baseline, 2330 (20%) had prediabetes. When accounting for diabetes that developed after the baseline period, they authors found no statistically significant association between prediabetes and dementia. Nevertheless, they found that earlier age of progression to T2D had the strongest association with dementia: a 3 times increased risk of dementia for those developing T2D before age 60 years; falling to a 73% increased risk for those developing T2D aged 60-69 years and a 23% increased risk for those developing T2D aged 70-79 years. At ages 80 years or older, developing T2D was not related to an increased risk of dementia.
The authors conclude: “Prediabetes is related to dementia risk, but this risk is explained by the event of diabetes. Diabetes onset at early age is most strongly related to dementia. Thus, stopping or delaying the progression of prediabetes to diabetes will substantially reduce the longer term burden of dementia.”
Source:
Journal reference:
Hu, J., et al. (2023) Prediabetes, intervening diabetes and subsequent risk of dementia: the Atherosclerosis Risk in Communities (ARIC) study. Diabetologia. doi.org/10.1007/s00125-023-05930-7.