A population-based study of the incidence of delusional infestation in Olmsted County, Minnesota, 1976-2010

BACKGROUND: Delusional infestation (DI) is a well-recognized clinical entity but there is a paucity of reliable data concerning its epidemiology. Knowledge of the epidemiology is fundamental to an understanding of any disease and its implications. Epidemiology is most accurately assessed using population-based studies, which are most generalizable to the wider population in the U.S. and worldwide. To our knowledge, no population-based study of the epidemiology (particularly incidence) of DI has been reported to date. OBJECTIVES: To determine the incidence of delusional infestation (DI) using a population-based study. METHODS: Medical records of Olmsted County residents were reviewed using the resources of the Rochester Epidemiology Project to confirm the patient's status as a true incident case of DI and to gather demographic information. Patients with a first-time diagnosis of DI or synonymous conditions between 1 January 1976 and 31 December 2010 were considered incident cases. RESULTS: Of 470 identified possible diagnoses, 64 were true incident cases of DI in this population-based study. The age- and sex-adjusted incidence was 1·9 [95% confidence interval (CI) 1·5-2·4] per 100 000 person-years. Mean age at diagnosis was 61·4 years (range 9-92 years). The incidence of DI increased over the four decades from 1·6 (95% CI 0·6-2·6) per 100 000 person-years in 1976-1985 to 2·6 (95% CI 1·4-3·8) per 100 000 person-years in 2006-2010. CONCLUSIONS: Our data indicate that DI is a rare disease, with incidence increasing across the life span, especially after the age of 40 years.