Dear Editor,

With the coronavirus disease 2019 (COVID-19) pandemic, families of intensive care unit (ICU) patients witnessed practice changes, such as the prohibition of hospital visits and reduced opportunities to see attending physicians [1]. Such changes might affect the mental status of a patient’s family, but previous studies were limited by the lack of controls [2, 3]. Moreover, it remains unclear whether the increased mental disorders were due to the COVID-19 pandemic itself or COVID-19 pandemic-related changes in ICU care for a family. Therefore, we aimed to examine the impact of COVID-19 pandemic-related changes in ICU care for the family on the mental status of spouses of ICU patients using a controlled interrupted time series design.

We used data on married couples from a large commercially available Japanese administrative database from DeSC Healthcare Inc. Tokyo, Japan, from April 1, 2019 to February 28, 2021. The study period was split into before and during the COVID-19 pandemic on April 1, 2020. Using the risk set matched-pair sampling method, we created matched pairs (1 case:10 controls) with cases being the spouse of a patient admitted to ICU and controls being spouses (matched by birth month and year, sex, and medical insurance status) of individuals who had not experienced ICU admission on the date of ICU admission for the case before and after April 1, 2020 (before COVID-19 and during COVID-19). The main outcome was the incidence of mental disorders within 90 days of the date of ICU admission for the cases. We conducted a controlled interrupted time series analysis that involved both before and during the COVID-19 pandemic comparison and comparison between spouses of ICU patients and matched controls [4]. Details are available in Supplemental Material.

Among 483,768 eligible spouses, we identified 5524 (1.1%) patients who were admitted to the ICU, and 5190 cases matched with 51,603 controls. Incidence of mental disorders within 90 days of the date of ICU admission for the cases was observed in 17.9% and 21.5% of the cases before and during the COVID-19 pandemic, respectively, and in 17% and 17.5% of the controls, respectively. The controlled interrupted time series analysis showed an upward level change in the cases compared with the controls during the COVID-19 pandemic (+ 4.5%, 95% confidence intervals + 0.01% to + 8.98%) (Fig. 1).

Fig. 1
figure 1

Change in the incidence of mental disorders before and during the COVID-19 pandemic in spouses of ICU patients and matched controls. Points represent the mean percentage of incidence of mental disorders within 90 days of the date of ICU admission for the cases in each month. Solid and dashed lines represent the predicted outcomes using controlled interrupted time-series analysis. April 2019 through March 2020 was the period before the COVID-19 pandemic, and April 2020 through February 2021 was the period during the COVID-19 pandemic. The red points and red solid lines represent the spouses of the ICU patient group and the blue points and blue dashed lines represent the matched control group. ICU intensive care unit; COVID-19 coronavirus disease 2019

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To our knowledge, this study is the first that examines the association between mental disorders in spouses of ICU patients and the COVID-19 pandemic by using a before-after design and by establishing an appropriate control. Although the present study had limitations (Supplemental Material), the controlled interrupted time series analyses results can provide strong evidence on public health events and rank second to randomized controlled designs in terms of its ability to control for bias [4]. Therefore, the observed increase in mental disorders among spouses of ICU patients calls for further studies to develop effective strategies, such as addressing barriers to care for family members of ICU patients using emerging technologies or investigating the health policy effectiveness of reopening ICU [5].