Mental disorders linked to subsequent dementia

A decades-long New Zealand national data base study suggests an association between mental disorders and subsequent dementia. The findings were published on February 16, 2022 in JAMA Psychiatry.

“In this population-based administrative register study of 1.7 million New Zealand citizens observed for 3 decades, people with early-life mental disorders were at elevated risk of subsequent dementia and younger dementia onset,” the authors said.  “Associations were evident across different psychiatric conditions, for Alzheimer disease and all other dementias, and after accounting for preexisting physical diseases and socioeconomic deprivation,” they added.

As background, the authors noted that discovering a potential link between mental disorders and dementia risk requires data that includes a full range of psychiatric conditions, data on mental disorders from early life and data that distinguishes between Alzheimer disease and related dementias.

This study included data on all persons born in New Zealand between 1928 and 1967 who resided in the country for any time during the 30-year observation period between July 1988 and June 2018.

The researchers gathered and analyzed data from the New Zealand Integrated Data Infrastructure, a group of sources linked at the individual level.

They determined diagnoses of dementia from public-hospital records, mortality records, and pharmaceutical records.

Of 1,711, 386 subjects included in the analyses, 866,301 (50.6%) were male and were aged 21 to 60 years at baseline.

The researchers reported that compared to subjects without a mental disorder, those previously diagnosed with a disorder were at 4.24-fold increased risk of developing dementia

Among subjects with dementia, those previously diagnosed with a mental disorder developed dementia 5.60 years (mean) sooner than those without a mental disorder.

After adjusting for preexisting chronic physical diseases and socioeconomic deprivation, the correlation held between mental disorder and subsequent dementia.

Compared to subjects without a mental disorder, increased risk of subsequent dementia ranged from 2.93-fold for prior neurotic disorders to 6.20-fold for prior psychotic disorders, and were evident for a subsequent diagnosis of Alzheimer disease (2.76-fold increased risk) and all other dementias (5.58-fold increased risk).

The authors concluded, “In this study, mental disorders were associated with the onset of dementia in the population. Ameliorating mental disorders in early life might also ameliorate neurodegenerative conditions and extend quality of life in old age.”