People with diabetes experience higher rates of long-term cognitive decline, new research suggests.
The study also found that worse control of blood sugar levels, whether someone is diabetic or not, could also lead to a decline in brain function later in life.
The research builds on previous data linking diabetes and cognitive capacity, by establishing a strong connection between overall blood sugar control and a subsequent risk of cognitive decline.
Researchers assessed participants' cognitive function using the English Longitudinal Study of Ageing - a representative database of over-50s in England which stores information about health, wellbeing and economic circumstances in several "waves", or time periods.
Information from the database is used to investigate the ageing process, including life expectancy and health trajectories.
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Scientists assessed cognitive function using data from wave two of the database (2004 to 2005), and reassessed every two years until wave seven (2014 to 2015).
Some 5189 men and women with a mean age of 66 took part. Their baseline levels of glycated haemoglobin (scientifically known as HbA1c) - a measure of blood sugar control - were monitored.
Researchers found that higher levels of glycated haemoglobin were strongly linked to a higher rate of decline in memory, executive function and cognitive function.
Their findings remained statistically significant even when factors such as age, sex, body mass index, alcohol consumption and heart disease were taken into account.
Researchers also discovered that a higher level of HbA1c was directly linked to a higher rate of cognitive decline, whether or not participants were diabetic.
The study was published in diabetes journal Diabetologia and led by scientists at the School of Public Health at Imperial College London and Peking University Clinical Research institute.
Researcher Dr Wuxiang Xie said: "Our study provides evidence to support the association of diabetes with subsequent cognitive decline.
"Our findings suggest that interventions that delay diabetes onset, as well as management strategies for blood sugar control, might help alleviate the progression of subsequent cognitive decline over the long-term."
