**2. Survey of the effects of COVID-19 on older people with underlying medical conditions**

#### **2.1 Survey on the influence of the spread of COVID-19 on living at home**

The Asian Working Group on Sarcopenia (AWGS) recommends establishing a balance between the prevention of COVID-19 and maintenance of function [19], as well as providing continued physical activity and daily living instructions to sustain activity levels and exercise opportunities while working to prevent infection and avoid functional decline. A systematic review of the impact of the spread of infection on rehabilitation found that all patients with COVID-19, regardless of infection status, had limited rehabilitation services [20], and a follow-up study found that community-dwelling older adults who lived alone or were less socially active tended to remain less active [21]. Older individuals with frailty or underlying conditions who live alone and have little social interaction may be at a particularly increased risk of developing frailty and disability.

Our hospital provides rehabilitation services to older patients not only during inpatient care, but also on an outpatient and home-visit basis. Under this situation, with the aim of discussing future interventions to maintain activity levels and function in older patients with underlying diseases, we conducted a survey on the impact of the spread of COVID-19 in older patients undergoing rehabilitation at our hospital [22].

#### **2.2 Impact of the pandemic in the patients who received rehabilitation**

We surveyed 175 patients aged 65 years or older receiving outpatient or in-home rehabilitation at our center regarding their activities before and during the spread of COVID-19. The results indicated that the frequency of going out for errands tended to decrease during the period of infection spread. On the other hand, the frequency of going out for health reasons tended to be divided into two groups: those who consciously went out and those who refrained from and reduced the frequency of going out. Regarding exercise, approximately half of the respondents reported engaging in some form of exercise during the COVID-19 pandemic, with the most common reference material being "nothing in particular" (**Figure 2**). The frailty group was classified into three groups based on scores on the Kihon Checklist and whether they required nursing care [17, 23]. Both the frailty and nursing care groups were significantly less likely to go out after the start of the infection spread (**Figure 3**).

### **2.3 Outcomes of older patients hospitalized with COVID-19**

The number of infected patients in Japan increased dramatically around January 2022 as the Omicron variant, which is associated with a lower mortality rate but greater infectiousness compared with the Delta variant, became the dominant strain [24]. Older individuals with pre-hospitalization frailty were found to be more likely to experience disability during acute treatment and a reduced ability to perform activities of daily living, even in relatively mild cases of COVID-19, and to sometimes require continued rehabilitation even after treatment is completed [25, 26]. We conducted a study using the Clinical Frailty Scale (CFS) to determine whether patients admitted to our hospital with a positive COVID-19 test result could be discharged directly home from the COVID-19 ward after the completion of acute care, depending on the severity of their frailty. The cutoff value on the CFS for not being discharged home [14] was six points (moderate frailty) or higher, with a sensitivity of 77.8% and specificity of 81.8% [27].
