The relationship between quality of life, Mini-Mental State Examination, and the Instrumental Activities of Daily Living in patients with Alzheimer's disease

Alzheimer's disease (AD) affects the cognitive function and capacity for independent living of the elderly, however little is known about the measurement of patient's overall health-related quality of life (HRQoL) and its relationship to these effects. We examined the relationship between patient/caregiver-rated HRQoL and cognition (using the Mini-Mental State Examination (MMSE)) or Instrumental Activities of Daily Living (IADL). One hundred AD patients participating in an open-label trial of donepezil were followed for 6 months. Cognition and function were assessed using the MMSE (clinician-rated) and IADL scale (caregiver-rated). Patient QoL, as assessed by the Assessment of Quality of Life (AQoL) scale, was rated separately by patients and their primary caregivers. Mean patient-rated AQoL was 0.60, whilst caregiver-rated AQoL was 0.50. Patient and caregiver AQoL assessments correlated (r = 0.37, P = 0.0038) for all levels of disease severity. Patient-rated AQoL scores ranged from 0.52 for patients with severe AD, to 0.71 for patients with mild AD. Caregiver-rated AQoL scores ranged from 0.40 to 0.59. There were approximately linear relationships between the AQoL and MMSE scores (patient-rated r = 0.30, P < 0.0001; caregiver-rated r = 0.28, P < 0.0001), and AQoL and IADL scores (patient-rated r = 0.36, P < 0.0001; caregiver-rated r = 0.43, P < 0.0001). Patient self-assessment of AQoL is a useful instrument for measuring HRQoL in AD that displays an approximately linear relationship with MMSE, IADL, and caregiver-rated AQoL.