Excess mortality among adults with mental disorders treated in psychiatric and general medical settings: A population-based cohort study using municipal medical claims data in Japan

Naoaki Kuroda; Nanako Tamiya

doi:10.1016/j.ajp.2023.103719

Excess mortality among adults with mental disorders treated in psychiatric and general medical settings: A population-based cohort study using municipal medical claims data in Japan

Asian J Psychiatr. 2023 Oct:88:103719. doi: 10.1016/j.ajp.2023.103719. Epub 2023 Jul 31.

Authors

Naoaki Kuroda¹, Nanako Tamiya²

Affiliations

¹ Health Services Research and Development Center, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki 305-8575, Japan; Health Department, Tsukuba City, 1-1-1 Kenkyu-Gakuen, Tsukuba, Ibaraki 305-0817, Japan; Department of Community Mental Health and Law, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-Higashi, Kodaira, Tokyo 187-8553, Japan. Electronic address: nkuroda@ncnp.go.jp.
² Health Services Research and Development Center, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki 305-8575, Japan; Department of Health Services Research, Institute of Medicine, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki 305-8575, Japan.

PMID: 37567083
DOI: 10.1016/j.ajp.2023.103719

Abstract

Objectives: To estimate the excess mortality associated with serious mental illnesses (schizophrenia and bipolar disorder) and common mental disorders (depression and anxiety) at the population level.

Methods: We conducted a population-based, retrospective cohort study in Tsukuba, Japan. Individuals aged 20-74 years and insured for at least 12 months by the National Health Insurance or Late Elders' Health Insurance as of April 2015 were included (n = 41,618, 29% of the city's population aged 20-74 years). Individuals with mental disorders (International Classification of Diseases-10 code: F00-F99) were identified in psychiatric and general medical services using medical claims during the 12-month baseline period and classified into mutually exclusive diagnostic subgroups. Their age/sex-adjusted all-cause mortality rate ratios (aMRRs) were estimated and compared to those of individuals without mental disorders.

Results: Altogether, 12.0% of participants had mental disorders (general medical service: 7.2% vs. psychiatric service: 4.8%). Common mental disorders were the most prevalent (8.1%). During the median 48 months of observation, 225 deaths were observed in people with mental disorders. The aMRR was 1.98 (95%CI: 1.70-2.29) for all mental disorders, with a higher rate ratio in psychiatric service than in general medical service users (aMRR: 2.64 [2.12-3.29] vs. 1.70 [1.42-2.04]), 3.57 (2.71-4.70) for serious mental illness, with a higher rate ratio in psychiatric inpatient service than in outpatient service users (aMRR: 5.74 [3.76-8.78] vs. 2.84 [2.00-4.04]), and 1.53 (1.27-1.84) for common mental disorders.

Conclusion: Serious and common mental disorders in psychiatric and general health services are associated with increased mortality in Japan.

Keywords: Common mental disorders; Mental disorders; Mortality; Serious mental illness.