In Alzheimer disease (AD), physical health problems can result from co
existing illness that is independent of the AD or can result directly
from the consequences of the brain disease. Most of these physical hea
lth problems are not unique to AD, but they may have more functional i
mpact in adults with AD. Coexistent or comorbid diseases may contribut
e directly to the outcomes of medical treatment. In future effectivene
ss 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 le
gitimate 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 co
morbid medical illness focus on system diseases and may not be applica
ble to the types of comorbid problems important to the AD patient. Fur
ther understanding of coexistent illness in AD may require the develop
ment of new measures of the cumulative occurrence of comorbid illness
in this population.