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Utility of the Quality of Life–Alzheimer's Disease Scale for mild cognitive impairment

FEW STUDIES ON the clinical characteristics of quality of life (QOL) in patients with mild cognitive impairment (MCI) have been reported. A QOL scale for MCI has not been established. Meanwhile, many QOL scales for Alzheimer’s disease (AD) have been developed. In particular, the Quality of Life–Alzheimer’s Disease Scale (QOL-AD), developed by Logsdon et al., is of great clinical utility. Logsdon et al. defined dementia-specific QOL as consisting of five domains: interpersonal, environmental, functional, physical, and psychological. The QOL-AD scale covers thirteen items: physical health, energy level, moods, living situation, memory, family, marriage, friends, overall self, ability to do chores around the house, ability to do things for fun, money, and overall life. The scale consists of two versions: a patient version and a caregiver version. The total score is calculated separately for the patient version and the caregiver version, with possible scores ranging from 13 to 52. The reliability and validity of the Japanese version of this questionnaire were confirmed by Matsui et al. Here, we examined the applicability of the Japanese version of the QOL-AD for patients with MCI. The subjects were 47 pairs, consisting of patients diagnosed as having amnesia-type MCI and their family members. The diagnosis of amnesic MCI was based on the criteria of Petersen as follows: (i) complaints of forgetfulness by the person himself/herself or by family members; (ii) maintenance of independent everyday life activities; (iii) no history of stroke or alcohol or drug dependence; and (iv) a Clinical Dementia Rating (CDR) of 0.5 and a Mini-Mental State Examination (MMSE) score of 25 or more. The mean age and the ratio of women were 76.5 6.5 years old and 40.4% among the patients and 62.3 14.0 years old and 82.9% among the family members, respectively. The average MMSE score was 26.9 points. We explained the study outline to the patients and their family members and obtained their written consent. All the patients completed the QOL-AD Japanese version, the MMSE, and Zung’s Self-Rating Depression Scale (SDS). In addition, all the family members completed the QOL-AD Japanese version, the Neuropsychiatric Inventory (NPI-Q), and the Hyogo Activities of Daily Living Scale (HADLS). SPSS 18.0 for Windows was used for the statistical analysis; the Spearman rank correlation coefficient was used to detect differences, and a P-value of less than 0.05 was regarded as significant. A good internal reliability was observed for both the patients’ responses (total score of subjective QOL-AD, 29.8 6.7; Cronbach’s alpha, 0.895) and the family members’ responses (total score of objective QOL-AD, 29.1 7.7; Cronbach’s alpha, 0.927). The concordance was moderate between the patients’ self-reports and the caregivers’ observations (rs = 0.57, P 0.001). The subjective QOL was correlated inversely with the SDS (rs = -0.688, P 0.001). On the other hand, the objective QOL was correlated inversely with the patient’s educational history (rs = -0.501, P = 0.041), the HADLS (rs = -0.553, P 0.001) and the patient’s SDS (rs = -0.422, P = 0.014). Moreover, no significant correlation was observed between either the subjective QOL and the MMSE and NPI-Q scores or the objective QOL and these scores. We confirmed an excellent internal and external reliability and demonstrated both the concurrent validity and the construct validity in our study of patients with MCI. First, in terms of the concurrent validity, we confirmed that a significant agreement existed between the total score determined from the patients’ self-reports and the caregivers’ observations. Previous studies had examined the construct validity of the QOL-AD to demonstrate the conceptual framework of the QOL-AD. These studies suggested that the presence of depressive symptoms in dementia subjects is the best predictor of the QOL-AD scores derived from both the patients’ self-reports and the caregivers’ observations. In addition, Logsdon et al. demonstrated that the activities of daily living (ADL) were significantly correlated with the QOL-AD score. Consistent with previous studies, we demonstrated that both the depressive mood assessed by the SDS and the ADL assessed by the HADLS were significantly correlated with the QOL-AD scores among MCI patients. Thus, the construct validity of the QOL-AD for patients with MCI was supported. Accordingly, the QOL-AD is applicable as a QOL assessment of patients with MCI. In the case of AD, the ‘mood factor’ (apathy and depression/dysphoria) in the NPI predicted the QOL-AD score obtained using both the patients’ and the caregivers’ responses. However, the depressive state assessed by the MCI patients and the ADL function may be important factors associated with both the patients’ and the caregivers’ responses to the QOL assessments.