Impact of the COVID-19 Pandemic on New Long-term Care Insurance Applications and All-cause Mortality in Older Adults in a Japanese Metropolitan Cohort: An Interrupted Time-series Analysis

BACKGROUND: New long-term care insurance (LTCI) certifications and mortality are key outcomes in cohort studies involving older adults; however, the coronavirus disease 2019 (COVID-19)'s comprehensive impacts on these outcomes remain underexplored. We examined the pandemic's impact on new LTCI applications and all-cause mortality in a metropolitan cohort. METHODS: In 2016, 15,500 individuals aged 65-84 years were randomly selected through stratified sampling from Ota City, Tokyo. LTCI and death records were tracked through December 2023; the monthly LTCI applications and all-cause deaths per 10,000 people were calculated. The COVID-19 pandemic period was defined as beginning in March 2020, after the World Health Organization Director-General characterized the situation as a pandemic on March 11, 2020. Interrupted time-series segmented regression analysis was used to compare trends pre- (January 2018-February 2020) and post-pandemic onset (March 2020-December 2023). RESULTS: From January 2018 to December 2023, 4,083 new LTCI applications and 2,457 deaths were recorded. New monthly LTCI applications showed a modest upward trend pre-pandemic (0.4 per 10,000 people; 95% confidence interval [CI], 0.1-0.8), declined sharply at the pandemic's onset (-9.6 per 10,000 people; 95% CI, -16.0 to -3.2), and subsequently increased at a higher rate than pre-pandemic levels (0.8 per 10,000 people; 95% CI, 0.6-1.0). Monthly all-cause deaths remained stable before and immediately after the pandemic's onset but rose slightly in the post-pandemic period (0.3 per 10,000 people per month; 95% CI, 0.2-0.5). CONCLUSION: The COVID-19 pandemic influenced both new LTCI applications and all-cause mortality in this study. These impacts should be carefully considered in cohort studies examining these outcomes.