Sudden Hearing Loss Could Indicate Future Stroke

A new study suggests that sudden loss of hearing might be an early sign of vulnerability to stroke, foreshadowing an actual cerebrovascular event by as much as two years.

Researchers at Taipei Medical University (Republic of China) conducted a five-year follow-up study of 1,423 patients included in a Taiwanese national medical insurance database. The patients were hospitalized for an acute episode of sudden sensorineural hearing loss (SSNHL), and their risk ratio for a stroke was compared to a control group of 5,692 patients who had been hospitalized for an appendectomy. Cox proportional hazard regressions were performed as a means of computing the five-year stroke-free survival rates after adjustment for possible confounding factors.

The study results showed that a total 621 patients (8.7%) had strokes during the five-year follow-up period: 180 (12.7%) from the SSNHL cohort and 441 (7.8%), of patients from the control cohort. After adjusting for other factors, the hazard of stroke during the five-year follow-up period was 1.64-times greater for SSNHL patients than for appendectomy patients. The study was reported in the June 26, 2008, edition of Stroke.

"Because this is the first time any association has been suggested, and because there were many limitations in the data, the results need to be interpreted cautiously until additional independent studies are performed,” said Professor Herng-Ching Lin, Ph.D., of the School of Health Care Administration. "Secondly, the database did not contain information regarding severity of hearing loss, extent of hearing recovery, tobacco use, body mass index, and the medical history of cardiovascular disease and atrial fibrillation - all of which can contribute to stroke risk.”

SSNHL is one of the most perplexing and controversial unsolved mysteries in otolaryngology. There is no universally accepted definition, but one useful definition is an idiopathic hearing loss of sensorineural origin, greater than 30 decibels in three contiguous frequencies, that occurs in less than three days. Most patients report onset of hearing loss within minutes to several hours. About one-third of patients will awaken with the loss; others may discover the problem when they try to use the telephone, or may describe a brief period of fluctuating hearing before the loss. About 50% of patients complain of concomitant unsteadiness or vertigo. Known etiologies include multiple sclerosis, Cogan's syndrome, Buerger's disease, macroglobulinemia, leukemia, sickle cell disease, polycythemia, syphilis, bacterial infection, mumps, ototoxic drugs, metastatic tumors, trauma, and lupus.


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