Prediabetes represents an intermediate stage characterized by elevated blood sugar levels that have not yet reached the threshold for a diagnosis of type 2 diabetes (T2D). A recent study highlights the significance of preventing the progression from a prediabetic state to type 2 diabetes, as it could lead to a significant reduction in future cases of dementia.
New findings recently published in the prestigious journal Diabetologia, the official publication of the European Association for the Study of Diabetes (EASD), shed light on the connection between type 2 diabetes (T2D) and the risk of developing dementia later in life. The study, conducted by PhD student Jiaqi Hu and Professor Elizabeth Selvin from the Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, USA, along with their colleagues, highlights how the risk of dementia increases as individuals develop T2D at earlier stages.
The primary focus of the research was to investigate the relationship between prediabetes and dementia. Prediabetes refers to an intermediate stage characterized by high blood sugar levels that have not yet reached the threshold for a T2D diagnosis. Although prediabetes carries a high risk of progressing to diabetes, it is also independently associated with various other clinical outcomes. Many individuals who eventually develop T2D pass through this phase of prediabetes before their diagnosis.
The study revealed a significant risk of transitioning from prediabetes to T2D. Among middle-aged adults with prediabetes, approximately 5-10% per year go on to develop T2D. Shockingly, a staggering 70% of individuals with prediabetes progress to T2D during their lifetime. In the United States alone, approximately 96 million adults are affected by prediabetes, making up 38% of the adult population.
In order to assess the potential connection between prediabetes and dementia, researchers examined data from participants in the Atherosclerosis Risk in Communities (ARIC) study. The study included individuals aged 45 to 64 years from four counties in the United States: Forsyth County, North Carolina; Jackson, Mississippi; suburbs of Minneapolis, Minnesota; and Washington County, Maryland. The data analysis focused on the period between 1990 and 1992, known as visit 2 of the study, when measurements of glycated hemoglobin (HbA1c), a marker of blood sugar control, and cognitive function were first recorded.
Cognitive function evaluations were conducted using a scoring system that involved three cognitive tests, administered during visits 2 (1990–1992) and 4 (1996–1998), as well as an expanded neuropsychological ten-test collection, implemented from visit 5 (2011–2013) onward. Informant interviews, including the Clinical Dementia Rating (CDR) scale and the Functional Activities Questionnaire (FAQ), were also utilized. Additionally, the Mini-Mental State Examination (MMSE) was administered. The participants were followed up until 2019.
For the purpose of this study, the researchers defined prediabetes as HbA1c levels ranging from 39 to 46 mmol/mol (5.7–6.4%). They also examined the subsequent diagnoses of type 2 diabetes (T2D) during the follow-up period.
They specifically aimed to determine the extent to which the association between prediabetes and dementia could be attributed to the subsequent development of type 2 diabetes (T2D) among individuals with prediabetes at the beginning of the study. Additionally, they explored whether the age at which diabetes was diagnosed influenced the risk of dementia.
The study involved analyzing data from the Atherosclerosis Risk in Communities (ARIC) study, which included 11,656 participants who did not have diabetes at the start of the study. Out of this group, 20% (2330 participants) had prediabetes. By accounting for the occurrence of diabetes that developed after the initial period, the authors did not find a statistically significant association between prediabetes and dementia.
However, the study did reveal that the age at which T2D developed had a significant impact on the risk of dementia. Individuals who developed T2D before the age of 60 had the highest risk, with a threefold increase in the likelihood of developing dementia. This risk gradually decreased as the age of diabetes diagnosis increased. Those who developed T2D between the ages of 60 and 69 had a 73% higher risk, while individuals who developed T2D between the ages of 70 and 79 had a 23% increased risk. Notably, individuals aged 80 years or older who developed T2D did not exhibit an elevated risk of dementia.
In summary, the study findings suggest that the association between prediabetes and dementia risk is not significant when considering the subsequent development of diabetes. However, the age at which diabetes develops appears to be a crucial factor, with an earlier onset of T2D associated with a higher risk of developing dementia.
“Prediabetes is associated with dementia risk, but this risk is explained by the development of diabetes. Diabetes onset at early age is most strongly related to dementia,” write the authors.
“Thus, preventing or delaying the progression of prediabetes to diabetes will substantially reduce the future burden of dementia.”
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