Incidence, prevalence, and surveillance for diabetes in New York State psychiatric hospitals, 1997-2004.

OBJECTIVE: The purpose of the study was to describe the incidence of newly treated diabetes mellitus, the prevalence of identified cases, and surveillance for new cases between 1997 and 2004 among inpatients in a large state psychiatric hospital system. METHODS: Prevalence was determined by ascertaining the number of individuals who received antidiabetic medication or had a diagnosis of diabetes mellitus for each calendar year in inpatient facilities operated by the New York State Office of Mental Health. Yearly incidence was calculated by identifying unique patients who received new prescriptions of antidiabetic medication among patients with no known history of receiving such medication and no recorded diagnosis of diabetes mellitus. Surveillance for abnormal plasma glucose levels was measured by calculating the number of plasma glucose tests completed per 100 patient-days among patients without diabetes mellitus. RESULTS: Prevalence of identified cases of diabetes increased from 6.9 percent of 10,091 patients in 1997 to 14.5 percent of 7,420 patients in 2004 (risk ratio [RR] = 2.11, 95 percent confidence interval [CI] = 1.93-2.31). Incidence of newly treated diabetes increased from .9 percent in 1997 to 1.8 percent in 2004 (RR = 2.03, CI = 1.51-2.73). The increase in incidence and prevalence was only partially explained by the increase in surveillance for new cases, which increased from 1.23 plasma glucose tests per 100 patient-days in 1997 to 1.80 in 2002 (RR = 1.46, CI = 1.43-1.50). CONCLUSIONS: The doubling of the treated incidence rate and the rise in prevalence of identified cases of diabetes among psychiatric inpatients mirrors the rise observed in the general population but with higher absolute rates.