• Sudden hearing loss;
  • sudden sensorineural hearing loss;
  • risk factors;
  • systematic review;
  • meta-analysis;
  • Level of Evidence: 2a



To review the medical literature evidence of potential risk factors for sudden sensorineural hearing loss (SSNHL) in the adult general population.

Study Design:

Systematic review of prospective and retrospective studies; meta-analysis of case-controlled studies.


Three researchers independently reviewed MEDLINE (January 1, 1950–November 30, 2010), Embase (January 1, 1980–November 30, 2010), and Evidence-Based Medicine Reviews databases in addition to conducting a manual reference search. Randomized controlled trials, prospective cohort studies, consecutive/nonconsecutive case series, and retrospective reviews in which a clear definition of SSNHL was stated were included in the study. Researchers individually extracted data regarding patient information and the presumed risk factors. Discrepancies were resolved by mutual consensus.


Twenty-two articles met the inclusion criteria. Cardiovascular risk factors (smoking, increased alcohol consumption) appeared to be associated with a higher risk of developing SSNHL. A low level of serum folate may also be implicated as a risk factor. Factor V Leiden and MTHFR gene polymorphisms were found to occur more frequently in patients with SSNHL in several studies, suggesting these inherited prothrombophilic mutations could be independent risk factors of SSNHL.


Acquired and inherited cardiovascular risk factors appeared to be associated with an increased risk of developing SSNHL.