Validation of the Japanese version of the Social Functioning in Dementia scale and COVID-19 pandemic's impact on social function in mild cognitive impairment and mild dementia.

Objectives: We aimed to psychometrically evaluate and validate a Japanese version of the Social Functioning in Dementia scale (SF-DEM-J) and investigate changes in social function in people with dementia during the coronavirus disease-19 (COVID-19) pandemic.

Design: We interviewed people with mild cognitive impairment (MCI) and mild dementia and their caregivers during June 2020-March 2021 to validate patient- and caregiver-rated SF-DEM-J and compared their scores at baseline (April 2020 to May 2020) and at 6-8 months (January 2021 to March 2021) during a time of tighter COVID-19 restrictions.

Setting: The neuropsychology clinic in the Department of Psychiatry at Osaka University Hospital and outpatient clinic in the Department of Psychiatry and Neurology at Daini Osaka Police Hospital, Japan.

Participants: 103 dyads of patients and caregivers.

Measurements: SF-DEM-J, Mini-Mental State Examination, Neuropsychiatric Inventory, UCLA Loneliness Scale, and Apathy Evaluation Scale.

Results: The scale's interrater reliability was excellent and test-retest reliability was substantial. Content validity was confirmed for the caregiver-rated SF-DEM-J, and convergent validity was moderate. Caregiver-rated SF-DEM-J was associated with apathy, irritability, loneliness, and cognitive impairment. The total score of caregiver-rated SF-DEM-J and the score of Section 2, "communication with others," significantly improved at 6-8 months of follow-up.

Conclusions: The SF-DEM-J is acceptable as a measure of social function in MCI and mild dementia. Our results show that the social functioning of people with dementia, especially communicating with others, improved during the COVID-19 pandemic, probably as a result of adaptation to the restrictive life.