Sudden Deafness Linked to Increased Risk of Stroke

By Todd Neale
TAIPEI, Taiwan,28 june 2008-- Sudden sensorineural hearing loss may signal an increased risk of a stroke within five years, researchers here found In a national healthcare database, those who were hospitalized with the condition were 1.64-fold more likely to have a stroke in the next five years compared with the general population (HR 1.64, 95% CI 1.31 to 2.07, P<0.001), Herng-Ching Lin, Ph.D., of Taipei Medical University, and colleagues reported online in Stroke: Journal of the American Heart Association. Those with sudden sensorineural hearing loss "should undergo a comprehensive hematologic and neurological examination to help clinicians identify those potentially at risk for stroke developing in the near future," they said.
Possible underlying causes of the sudden deafness include vascular occlusion, viral or bacterial infection, ruptured inner ear membrane, autoimmune diseases, and acoustic tumors, the researchers said.
Although some investigators had suggested that sudden sensorineural hearing loss may be an early sign of stroke, they said, no studies had examined the link between the two.
Using Taiwan's National Health Insurance Research Database, Dr. Lin and colleagues identified 1,423 patients who were hospitalized with sudden sensorineural hearing loss. For a control group representative of the general population, they selected 5,692 patients who had an appendectomy. All patients were followed for five years.
Patients with hearing loss were significantly more likely than the controls to have hypertension (P<0.001), diabetes (P<0.001), or hyperlipidemia (P=0.007) at the time of hospitalization.
They were also more likely to have a higher income and to live in the most urbanized areas and in the northern part of Taiwan (P<0.001 for all).
Overall, 621 (8.7%) patients had a stroke during follow-up -- 180 (12.7%) of those with hearing loss and 441 (7.8%) who had an appendectomy.
The researchers noted that almost half (49.4%) of the strokes in patients with hearing loss occurred more than two years after hospitalization. "This suggests that efforts to prevent the development of stroke should last for several years after an episode of sudden deafness."
The patients with hearing loss had a significantly lower five-year stroke-free survival than appendectomy patients (P<0.001).
After adjusting for cardiovascular risk factors, age, gender, level of urbanization, geographical location, and income, patients with hearing loss were 1.64-fold more likely to have a stroke within five years of hospitalization (P<0.001) than the controls.
As expected, all patients with hypertension, diabetes, and hyperlipidemia were at an increased risk of stroke (P<0.001 for all).
"Our finding supports a vascular origin in the pathogenesis of [sudden sensorineural hearing loss], at least in some patients," the researchers said, although the mechanism remains unclear.
They speculated that sudden sensorineural hearing loss shares an etiology with stroke because recent studies have shown that patients with the condition have significantly higher plasma fibrinogen and cholesterol levels than the general population.
One study speculated that the association between hearing loss and stroke "could be explained by the particular vulnerability of the cochlea to ischemia," a result of the high energy requirement of the inner ear and the lack of adequate collateral blood supply, they said.
The authors acknowledged that the study was limited because the database from which the patients were selected did not use a universal definition for sudden sensorineural hearing loss.
In addition, they said, the database did not contain information on the severity of hearing loss, extent of hearing recovery, tobacco use, body mass index, or medical history of cardiovascular disease and atrial fibrillation.
The authors made no financial disclosures.
Primary source: Stroke: Journal of the American Heart AssociationSource reference:Lin H-C, et al "Sudden sensorineural hearing loss increases the risk of stroke: a 5-year follow-up study" Stroke 2008; DOI: 10.1161/STROKEAHA.108.519090.