Polydipsia amongst adults with a learning disability in an institution

A hospital-based adult learning disabled population (n = 371) was screened for polydipsia with the help of a purpose-designed questionnaire. Polydipsia was defined as excessive drinking of more than 3 l of non-alcoholic fluid over a 24-h period. Altogether, 23 (6.2%) subjects were found to have polydipsia. The polydipsic group was compared with the whole hospital population on variables such as age and IQ distribution. A matched group of 23 individuals without a history of polydipsia was drawn from the same hospital population. The polydipsic and the matched group were compared using various biochemical and psychological measures. Thirty-five per cent of polydipsic patients, compared to 13% of the matched group, showed evidence of compensated hyponatraemia. This difference was not significant. There was no significant difference between the polydipsic and the matched group in the frequency of psychiatric illness, behavioural problems or autism. There also was no significant difference in the IQ levels of the polydipsic patients and the total hospital population. Polydipsia in this population is largely seen as part of an abnormal behavioural repertoire without any evidence of possible organic cause, except unidentified diabetes mellitus. Klein Levin syndrome and pica were represented in the polydipsic group, but not amongst the matched group.