The National Dementia Registry Study in Taiwan (T-NDRS) is an ongoing collaborative study conducted by the Institute of Population Health Sciences, Taiwan National Health Research Institute since 2017. Eight hospitals (three in northern Taiwan, two in middle Taiwan and three in southern Taiwan) participated in this project. All patients with dementia received clinical examinations, including a thorough survey of medical history, physical and neurological evaluations, laboratory tests (complete blood counts, serum B12 and folic acid, thyroid hormone levels, syphilis serology, routine biochemical tests) and brain image evaluations (computed tomography or magnetic resonance imaging). The T-NDRS aimed to investigate the baseline characteristics (including demographics, cognitive status, and other measures), cognitive and functional changes in patients with dementia and their caregivers’ burden. The T-NDRS study was approved by the ethics committees of the hospital sites. Written informed consent and permission for interviews were received from all study participants and their main adult caregivers.
Study overview and inclusion criteria
All participants received assessments, and their caregivers reported patients’ NPS and their own caregiver burden. General demographics and clinical information, such as history of major psychiatric diseases, neuropsychological and neuropsychiatric disturbances, functional disability, ADLs, and monthly income, physical activity per week were collected (16). For inclusion, patients in the age range between 65 and 90 years must had a diagnosis of dementia with a clinical dementia rating (CDR) score ≧0.5 (covering from very mild to severe dementia) and had at least one main caregiver defined as the person who frequently took care of/talked to/interacted with the dementia patient for at least 10 hours a week. The caregivers should accompany the dementia patients for the interview and annual follow-ups. The exclusion criteria for all participants included having any other central nervous system disease other than dementia, having psychosis not due to dementia, having alcohol use disorder or hepatic encephalopathy, or having expected life expectancy less than six months. Only caregiver-patient dyads aged ≧65 years old were analyzed in this study. From 2017 to 2019, 328 elderly patient-caregiver dyads (19.2%) were retrieved from the T-NDRS database (Figure 1).
The diagnosis of dementia type was made according to any of the following criteria: (1) NIA-AA criteria for Alzheimer’s disease (AD) (17), (2) NINDS-AIREN criteria for vascular dementia (18), (3) Lund-Manchester criteria of frontotemporal dementia (19), (4) 2015 International Dementia with Lewy Bodies (DLB) conference criteria for dementia with Lewy bodies (20), and (5) The Movement Disorders Society (MDS) criteria for dementia from Parkinson’s disease (21).
Assessment of questionnaire and scores
Mini-mental Status Exam (MMSE)
The MMSE is one of the widely used instruments for dementia. It provides a total score ranging from 0 - 30, with lower scores indicating greater cognitive impairment. It was administered to patients to obtain a global level of current cognitive function (22).
Clinical Dementia Rating Scale (CDR)
The severity of dementia was deﬁned according to the CDR (23). The CDR is based on inquiries of patients or informants concerning six areas of cognitive function. Each cognitive ability was scored as 0 = normal, 0.5 = questionable, 1 = mild impairment, 2 = moderate impairment, and 3 = severe impairment, from which an overall stage of dementia was derived.
Neuropsychiatric Inventory Questionnaire (NPI-Q)
The NPI-Q is a caregiver-based questionnaire in which the caregiver indicated the presence or absence of NPS in the demented patient during the last few weeks (24). The severity scale has scores ranging from 1 to 3 (1=mild; 2=moderate; and 3=severe). A total score for the NPI-Q was generated by summing all the individual severity scores.
Instrumental Activities of Daily Living Scale (IADL)
The Lawton Instrumental Activities of Daily Living Scale was used to evaluate independent living skills of the patients with dementia, which consisted of 8 domains of functions (25). Persons are scored according to their highest level of functioning in that category. A summary score ranges from 0 (low function, dependent) to 8 (high function, independent).
Zarit Burden Interview (ZBI)
The ZBI is a 22-item, self-report measure of perceived burden among caregivers. The instrument measures the caregiver’s emotion, psychological health, well-being, social and family life, finances, and degree of control over one’s life (26). Each question is scored on a 5-point Likert scale. Total scores can range from 0 (low burden) to 88 (high burden).
Categorical variables were presented by numbers with percentages, and continuous variables were presented by means with standard deviations. Chi-square tests and independent t-tests were used to compare categorical and continuous variables, respectively. Multivariable linear regression analysis was conducted to assess the associations between covariates and ZBI scores (caregiver burden). β values and their 95% confidence intervals (95% CIs) were calculated after adjustments in different models. Multivariable linear regression model 1 was adjusted for all variables listed in Table 1 except NPI total scores and NPI severity scores for the 12 items. Model 2 and model 3weremodel 1 plus adjusting for the total summed NPI severity scores or the severity score for each NPI item, respectively. Finally, the approaches of stepwise selection were applied in model 2 and model 3 to identify significant covariables for caregiver burden. All statistical analyses were performed using SPSS version 21.0(IBM, Armonk, NY, USA) with 2-tailed statistical tests. P values less than 0.05 were considered statistically significant.