The research is based on a cohort of twins in Sweden and published in Diabetologia, the journal of the European Association for the Study of Diabetes (EASD).
“Our findings highlight the need to control midlife diabetes to help prevent blockage or narrowing of cerebral arteries”
Accumulating evidence from previous studies suggests that type 2 diabetes is independently associated with an increased risk of cerebrovascular disease, especially ischaemic CBD.
Cerebrovascular disease (CBD) falls into two main classifications – ischaemic, in which the blood flow is restricted; and haemorrhagic, in which bleeding occurs.
The new study, conducted by researchers in Sweden and China, examined the link between type 2 diabetes in midlife and the risk of the different types of CBD in late life.
The study, by Tianjin Medical University and the Karolinska Institute, involved twins from the nationwide Swedish Twin Registry (STR), which started in the 1960s.
During 1998-2002, all living twins above 40 years of age were invited to participate in the Screening Across the Lifespan Twin study (SALT).
Of the participants in SALT, this latest study focused on 33,086 twins who were still alive on the follow up on 31 December 2014, of which 14,969 were men and 18,117 women
The study found no significant association between midlife diabetes and subarachnoid or intracerebral haemorrhage in late life.
However, individuals who developed type 2 diabetes at ages 40 to 59 years had double the risk of cerebral occlusion (artery narrowing) and a 30% higher risk of cerebral infarction (ischaemic stroke).
The mechanisms underlying the association of T2DM with cerebral infarction and occlusion of the cerebral arteries are complex, according to the study authors, and not completely understood.
They noted that individuals with type 2 diabetes developed dyslipidaemia – abnormal amounts of lipids in the blood – and accelerated atherogenesis – the formation of fatty deposits in the arteries.
In addition, metabolic disturbances such as insulin resistance, increased insulin production in response to this resistance, inflammation, increased fat deposits and abnormally high blood glucose in diabetes may also contribute to cerebrovascular events.
The authors suggested that an increase in the number of the endothelial cells lining the blood vessels, and thickening of the basement membrane, induced by diabetes lead to an increased risk of blocking of, but not rupture of the vessels.
They said this explained the negative association between the condition and haemorrhagic CBD (rupture of the arteries) and a positive association with ischaemic CBD (blockage of the arteries).
The authors said: “This large-scale, nationwide, population-based study of Swedish twins provides evidence that midlife type 2 diabetes is associated with some types of ischaemic CBD but not haemorrhagic CBD in the over 60s.
“Our findings highlight the need to control midlife type 2 diabetes to help prevent blockage or narrowing of cerebral arteries in late life and reduce the incidence of stokes caused by such blockages,” they added.