IN THE EIGHTH edition of his textbook, Kraepelin1 first noted that patients with late-onset variants of dementia praecox had atypical features and lacked the deterioration of personality typical in younger patients. Bleuler2 concluded that such late-onset cases of "schizophrenia" were rare, noting that only 15% of hospitalized patients had onset of symptoms after age 40 years, and a mere 5% after age 60 years. Assuming a lifetime prevalence of schizophrenia near 1%, the latter figure implies that the proportion of elderly people who will develop this condition is about 0.05%. Roth and Kay3,4 applied the term "late paraphrenia" to these cases, and noted the lack of a family history of schizophrenia (compared with younger-onset cases) and a preponderance of women. In their classic textbook, Slater and Roth5(p580) asserted that such illness accounted "for some89 percent of all first admissions (among women) over the age of 65." The relevant admission rates at the time (200-400 cases per 100 000) suggested a population prevalence among elderly women of 0.016% to 0.036% (this was presumably lower among men).5(p534) Thus, for decades it has been taught that isolated paranoid disorders among elderly people are rare.
Breitner JCS. Paranoid Psychoses in Old AgeMuch More Common Than Previously Thought?. Arch Gen Psychiatry. 2002;59(1):60-61. doi:10.1001/archpsyc.59.1.60