- 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,
‘Progression of cognitive impairment found to be directly correlated to HbA1c status whether diabetic or not.’
Data from wave 2 (2004-2005) to wave 7 (2014-2015
) of the English Longitudinal Study of Ageing
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.
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
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
Thus the results of the study do seem to
suggest that poor diabetes control
(measured by HbA1c status)
might significantly affect the rate of cognitive decline.
The authors say: "In conclusion, our
study provides evidence to support the association of diabetes with subsequent
cognitive decline. Moreover, our findings show
a linear correlation between circulating HbA1c levels and cognitive decline,
regardless of diabetic status"
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
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" Scores
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. 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
Lower z scores indicate lesser degree of
cognitive impairment while higher scores are associated with more severe