The findings of a prospective cohort study in Psychological Medicine identified the presence of a psychotic disorder in men as a significant predictor of dementia, although the specific mechanisms underlying this phenomenon have yet to be clarified.
The authors recruited 37,770 men aged 65 to 85 from the 1996 to 1998 Australian Electoral Roll. The men had no diagnosis of dementia at index. During the 17.7-year study, dementia developed in 21.4% (n=8068), and 23,999 (63.5%) died during follow-up. Dementia was defined according to International Classification of Disease guidelines.
Dementia developed approximately 3 times more frequently in people in whom a psychotic disorder was present. These disorders included schizophrenia, persistent delusional disorders, acute and transient psychotic disorders, schizoaffective disorders, and other non-organic or unspecified psychotic disorders. After adjusting for several competing risks (age, cardiovascular disease, respiratory disease, gastrointestinal disease, renal disease, cancer, hearing loss, depressive and bipolar disorders, and alcohol use disorder) the subhazard ratio remained at 2.67 (95% CI, 2.30-3.09).
The findings also suggested that more a more recent diagnosis of psychosis was a greater predictor of the development of dementia, as opposed to cases where patients had been living with a psychotic disorder diagnosis for 10 years or more.
A higher quality of life, including improved health care and living conditions, has been correlated with lower rates of dementia. The authors noted that whether dementia is preventable is not currently understood, but that the development of a psychotic disorder “may herald the early stages of a dementia syndrome, at least in some cases.”
A potential limitation of the study is the higher mortality rate associated with psychotic disorders. The investigators looked at men aged 65 and older, but it is possible that a number of individuals with psychotic disorders may have passed away before the age of 65, potentially eliminating relevant data from the study. Additionally, information about exposure to antipsychotic medications was not available.
Almeida OP, Ford AH, Hankey GJ, Yeap BB, Golledge J, Flicker L. Risk of dementia associated with psychotic disorders later in life: the health in men study (HIMS) [published online March 22, 2018]. Psychol Med. doi:10.1017/S003329171800065X