A Mayo Clinic study found that adverse events during polysomnography were relatively uncommon, with an event occurring on average once for every 623 PSGs.  The most common adverse events were cardiac in nature (29.3%), with a majority involving acute chest pain.  Falls were the next most common type of event (20.6%).  According to the authors, the findings suggest that future emphasis on improving patient safety should be oriented toward fall reduction, ensuring access to timely evaluation of acute medical problems, and thorough medical evaluation prior to PSG. The results are published in the November issue of the Journal of Clinical Sleep Medicine.