Idiopathic sudden sensorineural hearing loss (ISSNHL), or sudden deafness, is defined as an acute hearing loss of at least 30 decibels across three contiguous frequencies occurring over a 72-hour period. Although various theories on the underlying pathophysiology have been proposed (viral, vascular, immune-mediated) the cause of the hearing loss in most patients remains unknown.
However, consistent evidence supporting the various pathophysiologic hypotheses, prognostic associations, and even treatment recommendations for ISSNHL is scarce. Hence, Marc J. W. Lammers and associates from the BC Rotary Hearing and Balance Centre at St. Paul's Hospital (M.J.W.L., E.Y., B.D.W., J.L.), University of British Columbia, Vancouver, British Columbia, Canada conducted this systematic review and a meta-analysis assessing the risk of developing stroke and myocardial infarction after presentation with ISSNHL.
The authors included all studies investigating an association between ISSNHL and stroke and/or myocardial infarction (MI). Adhering to the MOOSE guideline, two independent reviewers extracted data, assessed risk of bias, and evaluated the relevance and quality of evidence.
The results showed that-
- Three observational studies evaluating the risk of stroke in ISSNHL were included (n = 6,521 patients).
- All individual study results indicated an increased relative risk of stroke after ISSNHL (unadjusted relative risk range 1.21–1.63).
- Pooled adjusted hazard ratios revealed a 1.42-fold increased risk of stroke after ISSNHL (hazard ratio [HR] 1.42; 95% confidence interval [CI] 1.15–1.75, I2= 55%).
- Subgroup analysis of one study demonstrated that the increased risk is only present in adults aged above 50 years (HR 1.23; 95% CI 1.07–1.42).
- Five observational studies evaluating the risk of MI in patients with ISSNHL were included (n = 61,499 patients).
- Pooled analyses demonstrated that ISSNHL was not associated with MI(HR 1.08, 95% CI 0.87–1.34).
Therefore, it was concluded that "ISSNHL may be an independent risk factor for the subsequent development of stroke especially in a sub-group of elderly patients."
However, they inferred that more studies are needed to confirm this association and to assess whether such patients would benefit from cardiovascular risk assessment and management to prevent future strokes.
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