Caregiver Burden and Neuropsychiatric Symptoms in Older Adults with Cognitive Impairment: The Aging, Demographics, and Memory Study (ADAMS)

Cognitive Evaluation

In the ADAMS, a nurse and a neuropsychology technician assessed all participants at their residence for cognitive impairment. The full details of the assessment and diagnostic procedures are described elsewhere.^19,20 During the assessment, the participant completed a battery of neuropsychological measures; a self-reported depression measure, (the Composite International Diagnostic Interview-Short Form (CIDI-SF));²¹ a standardized neurological examination; a blood pressure measurement; collection of buccal DNA samples for apolipoprotein E (APOE) genotyping; and a 7-minute, videotaped segment covering portions of the cognitive status and neurological examinations. Proxy informants provided information about the participant's cognitive impairment, functional limitations, neuropsychiatric symptoms, and medical history. The informant was usually a spouse or child (73%), and informants lived with the participant in just over half of the cases (53%). The ADAMS consensus expert panel of neuropsychologists, neurologists, geropsychiatrists, and internists reviewed all information collected during the in-home assessment and assigned cognitive diagnoses. Diagnoses were within three cognitive categories: normal cognitive function, cognitive impairment without dementia (CIND), and dementia. The Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition,²² and the Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition²³ criteria were used for diagnosis of dementia. CIND was defined as mild cognitive or functional impairment reported by the participant or informant that did not meet criteria for dementia, or performance on neuropsychological measures that was both below expectation and at least 1.5 SDs below published norms on any test within a cognitive domain (e.g., memory, orientation, language, executive function, praxis).

Those with dementia were classified by the stage or severity using the Clinical Dementia Rating (CDR) Scale,^24,25,26 a widely used assessment tool that stages the severity of dementia based on information obtained from both the participant and informant during the course of the evaluation. As in prior studies,^6,7,27 we defined mild dementia as CDR stage 0.5 or 1, moderate dementia as CDR stage 2, and severe dementia as CDR stages 3-5.

Neuropsychiatric Symptoms

The ADAMS assessed neuropsychiatric symptoms using the Neuropsychiatric Inventory (NPI). The NPI is a widely accepted measure of neuropsychiatric symptoms associated with cognitive impairment.^{28, 29} It collects information on symptoms during the past month in 10 domains -- delusions, hallucinations, agitation, depression, anxiety, elation, apathy, disinhibition, irritability, and aberrant motor behaviors -- using a structured interview of a knowledgeable informant. For each symptom reported by the informant, additional information is obtained on the frequency (4-point scale), severity (3-point scale) and caregiver distress (6-point scale) associated with the behavior. We defined symptoms as clinically significant if the product of the frequency and severity score of the reported symptom was 4 or higher.³⁰ Psychometric properties of the NPI have been previously reported.²⁸ The NPI has been validated in prior studies and has also been shown to have very good reliability (Cronbach's alpha was 0.88 for internal consistency reliability).²⁸

Quantity of Active Help and Supervision

In the ADAMS, each informant was asked about the quantity of active help provided for the subjects’ ADL/IADL limitations, as well as the amount of time spent supervising the subject to ensure safety. The questions were: “During the last month, how many days (and hours per day) did you provide active help to your friend or relative because of his/her health or memory problem?”, “During the last month, how many days (and hours per day) did you supervise your friend or relative to ensure safety, provide reassurance, or to make sure that nothing went wrong?” We calculated the intensity (number of weekly hours) of informal care using the average number of days in the prior month and average number of hours per day that informants reported providing active help and supervision to respondents.^11,31 We imposed a limit of 16 hours of care per day for any individual caregiver to allow for 8 hours of sleep.^11,32

Sociodemographic Characteristics

We obtained data on participants’ age (71-79, 80-89, ≥90 years), sex, race (white, black, other), and years of formal education (<12, 12, >12 years) from the ADAMS. Household net worth (categorized by quartiles), and marital / living status (married/partnered living together, unmarried living with other, unmarried living alone) were determined using data from the 2000 and 2002 waves of the HRS.

Medical Comorbidities

The HRS collects data on the presence of chronic medical conditions (heart disease, chronic lung disease, diabetes, cancer, musculoskeletal conditions, stroke, and psychiatric problems) in each wave of the survey.³³ Respondents report whether a physician has ever diagnosed each condition. We used data on chronic conditions from either the 2000 or 2002 wave of the HRS and included them in the analysis as dichotomous variables.

Statistical Analysis

We compared sociodemographic characteristics, total number of neuropsychiatric symptoms, and presence of individual neuropsychiatric symptoms across cognitive categories using chi-square tests. Since the goal of the analysis was to quantify the additional time for informal caregiving attributable to the presence of any neuropsychiatric symptoms, we adjusted for the presence of other factors that might independently affect the quantity of informal care, including sociodemographics, cognitive category, and medical comorbidities.

Because a substantial proportion of respondents received no informal care in the month prior to the assessment (e.g., 38% for active help, 33% for supervision), and because the distribution of informal caregiving time was highly skewed, we used a two-part multivariable regression model.^34,35 For the first part, we used logistic regression to determine the relationship of neuropsychiatric symptoms to the likelihood of receiving any informal care, adjusting for the potentially confounding factors noted above. For the second part, we used ordinary least squares linear regression to examine the association between neuropsychiatric symptoms and the natural log of informal caregiving hours among those who received any informal care, again adjusting for the same potentially confounding factors. The results from the two parts of the model were then combined to obtain an estimate of the unconditional effect (i.e., not conditioned on receiving any informal care) of number of neuropsychiatric symptoms and the presence of individual symptoms on the quantity of informal care received. For ease of interpretation, regression results from the two-part model were retransformed from log hours to hours.³⁶ We repeated the analysis with the variables for clinically significant neuropsychiatric symptoms (frequency score times severity score >=4) and compared these results with those from the previous analyses for the presence/absence of any neuropsychiatric symptoms.

All analyses were weighted and adjusted for the complex sampling design (stratification, clustering, and nonresponse) of both the ADAMS and the HRS.¹⁸ STATA, version 10.1 (Stata Corp, College Station, TX) was used for data analysis. All reported p values are two-tailed, and a p value < 0.05 was considered statistically significant.