Epidemiology
The condition is felt to be under-reported in the medical literature, where fewer than 100 cases have been studied. A series of 27 cases reported in 1999 (Hain et al. 1999) noted all but one patient to be female. The average age in this series was 49 years.
These trends have recently been confirmed by the MdDS Balance Disorder Foundation (http://www.mddsfoundation.org) in a study of over 100 individuals diagnosed with MdDS. The female:male ratio was approximately 9:1; the average age of onset was 43-45 years.
The most commonly reported inciting event was a prolonged ocean cruise (~45%), however shorter boating excursions (~22%), airplane travel (~15%), and automobile travel (~8%) have all been described.
Resource: Wikipedia
Mal de Debarquement Syndrome (or MdDS) is an imbalance or rocking/swaying sensation often both “felt” and “seen” by the sufferer that occurs after exposure to motion (most commonly after a sea cruise or a flight). Although other forms of travel have been known to trigger it.