Dementia severity and the longitudinal costs of informal care in the Cache County population

Abstract

Background: Dementia costs are critical for influencing healthcare policy, but limited longitudinal information exists. We examined longitudinal informal care costs of dementia in a population-based sample.

Methods: Data from the Cache County Study included dementia onset, duration, and severity assessed by the Mini-Mental State Examination (MMSE), Clinical Dementia Rating Scale (CDR), and Neuropsychiatric Inventory (NPI). Informal costs of daily care (COC) was estimated based on median Utah wages. Mixed models estimated the relationship between severity and longitudinal COC in separate models for MMSE and CDR.

Results: Two hundred and eighty-seven subjects (53% female, mean (standard deviation) age was 82.3 (5.9) years) participated. Overall COC increased by 18% per year. COC was 6% lower per MMSE-point increase and compared with very mild dementia, COC increased over twofold for mild, fivefold for moderate, and sixfold for severe dementia on the CDR.

Conclusions: Greater dementia severity predicted higher costs. Disease management strategies addressing dementia progression may curb costs.

Keywords: Alzheimer's disease costs; Costs; Dementia longitudinal costs; Longitudinal caregiving costs; Longitudinal informal dementia.

Figure 1. Average Daily Costs of informal care increase with severity of dementia

The distribution of average daily costs of care by CDR score at final visit are depicted below in 2012 dollars (corrected using MCPI for average Utahn wages) to show the unadjusted effect of dementia severity on average daily costs of care. The heavy black lines within each “box” and the heavy red lines represent median and mean daily costs of care respectively. Lower and upper box edges represent the 25^th and 75^th percentiles respectively, while circles and asterisks represent outlier (1.5 * interquartile range) and far outlier (3.0*interquartile range) values respectively. While daily cost of care data were non-normally distributed (highly skewed); all means were significantly different from one another. N = 283† † Of the 287 subjects, four were missing CDR at their final assessment and thus excluded from this figure.

Figure 2. a–2b. Change in the cost of informal dementia care by MMSE and NPI scores over time

Figure panels 2 displays the informal dementia care costs in the fully adjusted, time-varying MMSE model for an individual without vascular dementia, at least a high school education, and in good/excellent health. Panel 2a displays the change in informal care costs by time and MMSE score holding NPI score constant at 10 (median of all time points). For illustration, the corresponding informal care costs associated with an MMSE of 20 with dementia duration of 4 years = $28/day; the informal care costs associated with an MMSE of 10 with dementia duration of 7 years = $66/day. Panel 2b displays the change in informal care costs by MMSE and NPI holding time constant at 3.7 years (median of all time points). For illustration, the corresponding informal care costs at an MMSE of 20 with NPI score of 10 = $27/day; the informal care costs associated with an MMSE score of 10 and NPI score of 30 = $74/day.

Figure 3. Change in the cost of informal dementia care by CDR over time

Figure 3 displays the informal dementia care costs in the fully adjusted time-varying CDR model for an individual without vascular dementia and in good/excellent health. For illustration, the corresponding informal care costs associated with a CDR of 1 (mild) with dementia duration of 4 years = $11/day; the informal care costs associated with a CDR of 3 (severe) with dementia duration of 7 years = $62/day. CDR values are: 0.5 (very mild), 1 (mild), 2 (moderate), 3 (severe).