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.

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.

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.

103 dyads of patients and caregivers.

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

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.

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.

Capgras syndrome is a delusion in which the patient believes that a particular individual has been replaced by an imposter. It is observed in patients with psychiatric disorders such as schizophrenia but also occurs in patients with a neurodegenerative disease including Lewy body disease and Alzheimer’s disease. Here we report a patient with early-onset Alzheimer’s disease who presented with a unique form of Capgras syndrome.

An early 60’s right-handed woman with 12 years of education, visited our outpatient clinic for evaluation of her memory impairment. Neurological examination was not remarkable. A MMSE score was 25/30 and a neuropsychological examination indicated mild impairment of attention and episodic memory, and relatively preserved visuospatial function. Six months after the initial visit of our clinic, she started to claim that she met several imposters of her husband. She called each imposter in different name, described each as a slightly different appearance, and expressed different level of sense of familiarity. An additional examination of face recognition using photographs of her husband revealed that there was a difficult to recognize her husband especially viewed from the side of his face. In addition, she showed a difficulty in discriminating between two different unknown faces and in judging approximate age of face in photographs. Brain MRI showed no significant atrophy and IMP-SPECT showed an extensive hypoperfusion in the bilateral, right-side dominant temporal, parietal, and occipital lobes. Both FP-CIT SPECT and MIBG scintigraphy were negative. Florbetapir PET was positive. Thus, a diagnosis of early-onset Alzheimer's disease was made. Acetylcholinesterase inhibitors and antipsychotics were used to treat her Capgras syndrome, but the symptom lasted for more than a year.

There are several possible factors that may induced patient’s unique Capgras syndrome: (1) psychodynamic background- the patient and her husband had been in a long-term common-law relationship; (2) mild impairment in face recognition; (3) dysfunction of right hemisphere, which is known to be strongly related to Capgras syndrome. The combination of these factors may result in the occurrence of multiple imposters of her husband with different degrees of familiarity.

The present study aimed to compare the social function between mild cognitive impairment (MCI), mild Alzheimer’s disease (AD) dementia, and mild dementia with Lewy bodies (DLB) using the Japanese version of Social Functioning in Dementia scale (SF-DEM-J).

We interviewed 103 patients and family caregivers from June 2020 to March 2021: 54 patients with MCI, 34 with mild AD dementia, and 15 with mild DLB. We compared the caregiver-rated SF-DEM-J, Clinical Dementia Rating (CDR), MMSE, age, length of education, Geriatric Depression Scale (GDS), the University of California, Los Angeles Loneliness Scale (UCLA-LS), Neuropsychiatric Inventory (NPI), and informant version of the Apathy Evaluation Scale (AES) between MCI, mild AD dementia, and mild DLB groups using Kruskal-Wallis test with Dunn-Bonferroni correction for post-hoc analyses. We compared sex, living situation, and caregiver demographics between three groups using chi-square test. We performed correlation analysis between the score of each psychological test and the scores of SF-DEM-J within group using Spearman’s rank correlation coefficient.

For SF-DEM-J, the score of section 2 (communicating with others) was significantly worse in mild AD dementia than in mild DLB. The scores of section 1 (spending with others) and section 3 (sensitivity to others) and the total score did not significantly differ between three groups. The score of section 1 was significantly associated with MMSE in MCI, with anxiety and disinhibition of NPI, and AES in mild AD dementia, and with GDS in mild DLB. The score of section 2 was significantly associated with AES in MCI and mild AD dementia, with UCLA-LS in MCI, and with the length of education in mild DLB. The score of section 3 was significantly associated with agitation and irritability of NPI in MCI and mild AD dementia. The total score was associated with UCLA-LS and AES in MCI, and with AES in mild AD dementia.

Factors affecting social functioning differed between MCI, mild AD dementia, and mild DLB. Apathy, agitation and irritability affected social functioning in MCI and mild AD dementia while depressive mood affected social functioning in mild DLB.