In July of 1998 Periodic Paralysis International conducted a survey of 64 self-reported medically diagnosed patients from among its membership. The questionnaire underwent no formal validation process, nor was the data assessed by personnel trained in this field. Most participants fell between 26-55 years of age. All participants under 25 years of age were male. Several families could trace the presence of symptoms back three or more generations through family records.
Female participants report more total years with symptoms compared to male participants.
Male diagnostic delay from 3 hours to 21 years. Ninety-two percent of female participants were initially misdiagnosed. Even females with brothers and fathers who had been diagnosed and were being treated for periodic paralysis had symptoms attributed to psycholgical factors or described as 'emotional in origin'. Participants who were misdiagnosed or whose symptoms were attributed to psychological origins experienced significant diagnostic delay. Several have since been genotyped.