Real-world data from Japan indicate that organic mental disorders, such as Alzheimer’s disease and delirium, are major risk factors for COVID-19 infection and hospitalization among adults aged 60 years and older. Analysis of the Japanese Health Insurance Database showed higher vulnerability in this population, highlighting the need for targeted prevention and monitoring strategies. The study was published in the International Journal of Infectious Diseases by Takuya U. and colleagues.
While COVID-19 has been known for its acute respiratory symptoms, there is increasing evidence that its effects are not limited to the acute phase of infection. In particular, mental and behavioral disorders are being identified as significant sequelae of infection. The purpose of this study was to assess disease risk associated with COVID-19 based on pre-infection health conditions and the development of new sequelae in hospitalized older adults in Japan.
The study utilized the Japanese Health Insurance Database to search for patients aged 60 years who were newly diagnosed with COVID-19 and were hospitalized until December 31, 2020. A total of 8,072 patients were included in the study, consisting of 4,036 patients with COVID-19 and 4,036 controls without COVID-19. Matching was done in a 1:1 ratio based on age, sex, and index date to make the two groups comparable.
Two different methods of analysis were done. First, a case-control analysis using conditional logistic regression with least absolute shrinkage and selection operator (LASSO) was done to find the diseases that are associated with COVID-19 infection. Second, a retrospective cohort analysis using time-to-event analysis was conducted to assess the risk of new diseases after COVID-19 infection.
Key findings
In the pre-infection analysis, organic mental disorders, including symptomatic mental disorders, had the strongest association with COVID-19, with an odds ratio of 2.276, which means more than double the risk compared to controls.
In the post-infection analysis, behavioral syndromes associated with physiological disturbances and physical factors had the highest risk of developing new conditions after COVID-19 infection, with a hazard ratio of 3.523 (95% CI, 2.101-5.907).
In addition, pulmonary heart disease and diseases of the pulmonary circulation were significantly more prevalent after COVID-19, with a hazard ratio of 2.954 (95% CI, 1.360-6.420).
These results emphasize that both neuropsychiatric and cardiopulmonary diseases are important constituents of post-COVID morbidity in the elderly.
This large real-world study from Japan clearly shows the association between COVID-19 and the risk of mental, behavioral, and respiratory disorders in people aged 60 years and above. The results clearly show that COVID-19 has long-term health implications and emphasize the need for long-term follow-up to manage the mental and behavioral aspects of this high-risk group.
Reference:
Uematsu, T., Nojiri, S., Nagao, M., Ishijima, M., & Nishizaki, Y. (2026). Comprehensive analysis of risk factors for Coronavirus disease 2019 infection and post-infection sequelae based on real-world data from a health insurance database in Japan. International Journal of Infectious Diseases: IJID: Official Publication of the International Society for Infectious Diseases, 108405. https://doi.org/10.1016/j.ijid.2026.108405
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