Very Mild Dementia and Medical Comorbidity Independently Predict Health Care Use in the Elderly

Studies that assess health care use in older adults with and without dementia face several major challenges. These include ascertaining dementia status, measuring health care use, and adjusting for comorbidities. Most studies rely either on patient and informant reports or on medical claims data. Claims-based studies show that older adults with dementia use more medical care and incur higher medical costs than older adults without dementia.1–3 In these studies, the use of medical claims data to establish dementia cases creates at least two methodological issues. First, use of claims data likely underestimates true dementia-related utilization, as such data cannot capture undiagnosed dementia or the prodromal states preceding frank dementia. Second, because the same data are used to capture dementia cases and to measure outcomes, persons with higher costs may be preferentially ascertained, resulting in ascertainment bias.4 Studies using claims-based data are therefore vulnerable to the twin problems of underestimating total utilization and cost, while overestimating the health care costs per person. Studies that rely on patient and informant reports often use research quality evaluations to determine dementia status, which generally provide more consistent ascertainment of dementia status.5,6 However, these studies may need to rely on informants to obtain medical history and determine patterns of health care use. Abundant evidence suggests that such informant-based reporting is subject to bias, often failing to report utilization.7,8 Assessing the role of comorbidities is a third challenge. Serious medical conditions that are common in people with dementia increase the use and cost of health care services.9 If comorbidites increase utilization independent of dementia status, any estimate of dementia burden should adjust for them. On the other hand, if comorbid disease is mediated by dementia status, then adjusting may lead to underestimates of dementia-attributable utilization. To address these challenges, we systematically screened and diagnosed dementia in older adults participating in a longitudinal cohort study of dementia screening strategies in an urban geriatrics practice. To capture the range in severity of comorbidities, we then used the Cumulative Illness Rating Scale-Geriatrics (CIRS-G) a well validated measure of chronic medical burden for geriatric patients that indicates number and severity of comorbid disease.10,11 We avoided reliance on informant reports by reviewing medical charts to compile the CIRS-G. Finally, we used hospital-based claims data to assess utilization, focusing on emergency department (ED) visits and hospital admissions for 5 years following our initial assessment. We expected that patients with very mild dementia would have more ED visits and hospitalizations than patients without dementia. This is because very mild dementia, which often goes unrecognized in primary care,12–14 may lead to poor adherence to medication and lifestyle management and a failure to optimally manage medical comorbidities.15 This, in turn, may increase the use of acute care services and exacerbate cognitive impairment.1,5,16 Medical burden was expected to be a powerful predictor of both ED visits and hospital admissions as it is in most studies of dementia. 9 Finally, we sought to determine whether dementia status and medical burden were independent predictors of ED visits and hospitalizations.