Assessing physical status in Alzheimer disease research

In Alzheimer disease (AD), physical health problems can result from coexisting illness that is independent of the AD or can result directly from the consequences of the brain disease. Most of these physical health problems are not unique to AD, but they may have more functional impact in adults with AD. Coexistent or comorbid diseases may contribute directly to the outcomes of medical treatment. In future effectiveness studies in AD, in addition to measuring the severity of the AD, the presence and severity of coexisting illness should also be evaluated. In addition to accounting for comorbidity as part of AD effectiveness research, the reduction of comorbid physical illness may also be a legitimate independent outcome measure to target in the effectiveness of the clinical care provided to patients with AD. Examples of existing measures of comorbidity include the Charlson comorbidity index and the Greenfield index of coexistent disease. These existing measures of comorbid medical illness focus on system diseases and may not be applicable to the types of comorbid problems important to the AD patient. Further understanding of coexistent illness in AD may require the development of new measures of the cumulative occurrence of comorbid illness in this population.