- Cognitive impairment refers to a mental state when a person has difficulty concentrating, remembering things, learning new things, or making decisions that affect their daily life.
- Diabetes is a metabolic disorder marked by high blood glucose levels affecting approximately 400 million persons worldwide
- Cognitive decline found to be faster in diabetics with sub-optimal control compared to persons with good diabetic control.
controlled diabetes could lead to a faster rate of long term cognitive decline
compared to persons with good diabetic control, according to a recent study
published in Diabetologia, the journal of the European Association
for the Study of Diabetes (EASD).
The study included data drawn from English Longitudinal Study of Ageing, led by Dr Wuxiang Xie, School of Public Health, Imperial College London, London, UK, and Peking University Clinical Research Institute, Beijing, China, and colleagues.
Data from wave 2 (2004-2005) to wave 7 (2014-2015) of the English Longitudinal Study of Ageing (ELSA) were assessed to determine cognitive decline. Wave 2 included baseline data with subsequent waves (3 to 7) at two yearly intervals. Any possible associations were found using computer simulations.
Correlation Between Cognitive Decline and Diabetic Control
- The study consisted of 5189 participants (mean age 66 years, 55 percent women) with baseline HbA1c values ranging from 15.9 to 126.3 mmol/mol (3.6-13.7%)
- Follow-up was for an average duration of eight years with an average of five cognitive assessments during this period
- A 1 mmol/mol increase in HbA1c showed significant increase in rate of cognitive decline measured by memory z scores, global cognitive z scores, and executive function z scores
- The rate of decline was higher in persons with higher HbA1c levels during the course of the study irrespective of their HbA1c status at baseline
- Even after adjustment for other factors such as baseline age, sex, current smoking, alcohol consumption, high blood pressure, body mass index (BMI), education, marital status, total cholesterol, triglycerides, depressive symptoms, heart disease, stroke, and chronic lung disease this association was significant
Further studies to establish the effect of maintaining good diabetic control in relation to cognitive decline are needed to strengthen the association.
However, strategies to delay diabetes onset and optimal management and control of blood sugar levels (which are even otherwise desirable) may retard the rate of cognitive decline in diabetic patients.
What is HbA1c?HaA1c or glycated hemoglobin is formed when the glucose combines with the hemoglobin in the red cells. This glycated hemoglobin can be measured and reflects the blood glucose levels over a period of 8-12 weeks (the average lifespan of red cells). This is a more reliable index of diabetic control, as it gives a longer term control instead of day-to-day changes in blood glucose levels due to dietary and other factors (HbA1c can be high even if blood glucose levels on the day are normal).
A higher level of HbA1c indicates that diabetic control is sub-optimal and is associated with higher risk of complications. Thus doctors treating diabetic patients aim to optimize HbA1c levels.
Assessment of Cognition - Arriving at "z" ScoresCognitive impairment refers to a mental state when a person has difficulty concentrating, remembering things, learning new things, or making decisions that affect their daily life. Cognitive impairment can be mild to severe. Persons with mild impairment may be able to recognize something is wrong but are still able to cope. With severe impairment a person is unable to understand simple things or perform simple tasks or even speak coherently resulting in an inability to be independent for activities of daily living.
Raw scores obtained by doing a series of cognitive tests on the patients are converted to z scores by statistical methods, using mean and standard deviation at baseline. These individual 'z' scores are then averaged to obtain the summary of global cognitive function.
Lower z scores indicate lesser degree of cognitive impairment while higher scores are associated with more severe impairment.