Mortality over a 20-year period in patients with primary polydipsia associated with schizophrenia: A retrospective study

Primary polydipsia, excessive fluid intake without medical cause, is present in over 20% of seriously and persistently ill psychiatric inpatients. The long-term effects of primary polydipsia on longevity have not previously been examined. Inpatients in a psychiatric hospital were screened for polydipsia in 1985. Those identified to be polydipsic, the majority of whom suffered from schizophrenia, were re-evaluated in 2005 and compared with a control group of non-polydipsic patients. Chart reviews were conducted and follow-up data were obtained. Of 172 patients at the time of screening, 48 suffering from schizophrenia either had or went on to develop polydipsia; 42 non-polydipsic patients with schizophrenia from the original survey were randomly selected as controls. Primary polydipsia had a significant negative effect on longevity. The median age at death (age at which 50% of cases have died) was 59 years for polydipsic patients and 68 for non-polydipsic control patients. Adjusting for duration of schizophrenia, smoking, and diagnosis, a patient with polydipsia had a 74% greater chance of dying before a non-polydipsic patient (a hazard ratio of 2.84 [95% Confidence Interval (Cl): 1.22-6.64]). Outcome was worst in patients with severe polydipsia: the median age at death was 57 years and a patient with severe polydipsia had a 75% greater chance of dying before a non-polydipsic patient (hazard ratio of 3.36 [95% CI: 1.31-8.60]). When polydipsia is associated with schizophrenia, mortality is increased in comparison to that in patients with schizophrenia who do not drink water to excess. (C) 2008 Elsevier B.V. All rights reserved.