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Diabetes is a well-established risk factor for stroke. It can cause pathologic changes in blood vessels at various locations and can lead to stroke if cerebral vessels are directly affected, writes Dr P C Mohan

Stroke is a major global health problem. It is the third leading cause of death and the fourth leading cause of disability worldwide. The incidence of stroke is increasing in India by 100% with an increase in mortality by 26%. Stroke is more common in urban areas than in rural India and is a significant public health problem draining health, and human resources, causing maximum economic burden.

A stroke happens when blood flow to a part of the brain is cut off. Without blood flow and oxygen supply, brain cells start dying within minutes causing infarction. Stroke can happen due to leakage or rupture of the blood vessels leading to haemorrhage.

The symptoms of a stroke are speech problems, facial drooping, limb weakness, visual disturbances, unsteady gait and loss of consciousness depending on the area of brain involvement.

There are two main types of stroke. Ischaemic stroke constitutes 85% of cases due to fatty deposits or clots blocking the blood flow while haemorrhagic stroke is about 15% due to leakage or rupture of blood vessels.

A positive and significant association exists between diabetes and ischaemic stroke. Diabetes is a major independent risk factor for stroke. The crude incidence of stroke
among diabetics is three times greater than the general population. 30% of patients who had a stroke had diabetes. Diabetes causes several metabolic and pathological changes that lead to strokes like arterial stiffening, systemic inflammation, endothelial dysfunction and heart failure.

Patients with glucose intolerance have double the risk of stroke compared to non-diabetics. The relative risk is greater in women than in men. The relative risk of stroke in persons with diabetes reaches a maximum at 40-60 years of age.

Patients with stroke are more likely to have undiagnosed diabetes and glucose intolerance. The prevalence of thromboembolic but not haemorrhagic stroke increases when serum glucose levels are more than 126 mg. Proteinuria also appears to be a risk factor for stroke in people with impaired glucose intolerance and diabetes.

Glucose levels of more than 140mg reduced the beneficial effects of early restoration of blood flow leading to worse outcomes despite plasminogen activator-induced recanalisation. Hyperglycemia increases brain lactate production facilitating the conversion of hypoperfused tissue into infarction.

There is an increase in both short-term and long-term mortality in diabetes who had a stroke. After 5 years only 20% of diabetics were alive compared to 40% of non-diabetics. Studies have shown patients with glucose levels less than 120mg had a complete recovery from hemiparesis within the first month. 70% of patients with less than 120mg and only 30% with more than 120mg were able to return to work.

Hence it is necessary to control blood glucose for better stroke outcomes and prevention of further microvascular complications.

The coincidence of two risk factors namely hypertension and diabetes doubles the risk of stroke. Hypertensive diabetic patients are at substantially increased risk of primary and secondary stroke.

Identifying risk factors for stroke early helps in establishing prevention strategies in the population thereby reducing the incidence of stroke.

(The author is a senior consultant neurologist with a leading chain of hospitals in Bengaluru.)