text: Comorbidities 
  Charlson comorbidity index (CCI) 
  The Charlson Comorbidity Index was used to measure 
  the presence of chronic comorbid medical conditions 
  [34]. It lists 19 medical conditions that participants are 
  asked to indicate whether they “have ever been diag- 
  nosed with by a physician”. Conditions are weighted 
  and added for an overall measure of comorbidity 
  burden. The CCI has demonstrated good test-retest re- 
  liability (0.91) and positive but weak to modest correla- 
  tions with medication use, hospitalizations, 
  length of 
  total charges, and pharmacy and laboratory 
  stay, 
  charges for older adults in general medical care and 
  surgical care settings [35]. 