RT Journal Article SR Electronic T1 Normal pressure hydrocephalus (NPH): more about NPH by a physician who is the patient JF Clinical Medicine JO Clin Med FD Royal College of Physicians SP 162 OP 165 DO 10.7861/clinmedicine.11-2-162 VO 11 IS 2 A1 Harold O Conn YR 2011 UL http://www.rcpjournals.org/content/11/2/162.abstract AB The incidence of idiopathic normal pressure hydrocephalus (INPH) is seen to be relatively rare, ie about two per million inhabitants per year. Five studies on the prevalence of INPH in elderly patients, from three countries, have been published between 1985 and 2009.1–5 Prevalence ranged from 0.41% to 2.94% (mean 0.8%), ie slightly less than one per 100 based on samples ranging from 170 to 982 subjects. This surprisingly high percentage was not found in a survey that attempted to identify every person with INPH in a small county in Norway with a population of 219,748. Attempts to identify all patients with INPH overlook many cases. INPH is actually a very common disease and its prevalence increases with age.