Cognitive function is maintained in noninstitutionalized elderly Japanese requiring care with high levels of health-related quality of life

Abstract

Background: Health-related quality of life (HRQOL) has been reported to be associated with cognitive function; however, whether or not this relationship involves causality is uncertain. This study aimed to determine whether HRQOL levels are associated with subsequent changes in cognitive function in elderly people requiring care. Methods: Participants were 74 community-dwelling elderly people utilizing the long-term care service (69 % women) who underwent physical and psychological examinations at baseline and follow-up. The outcome was 2-year changes in Mini-Mental State Examination (∆MMSE) score. The potential predictor was HRQOL level assessed by the EuroQol 5 dimension (EQ-5D) score (utility value) at baseline; other variables were body mass index (BMI), Barthel index, grip strength, Geriatric Depression Scale, serum albumin, and serum hemoglobin. Associations between EQ-5D and ∆MMSE scores were assessed using correlation analysis, regression analysis, and analysis of covariance (ANCOVA). Results: Mean age, BMI, and Barthel index at baseline were 81.6 years [standard deviation (SD) 8.2], 21.1 kg/m2 (SD 4.0), and 79 (SD 20), respectively; the mean ∆MMSE score was –2.2 (SD 5.1). EQ-5D was significantly correlated with ∆MMSE (partial r = 0.375, P = 0.0012). The mean ∆MMSE values of the 1st, 2nd, and 3rd EQ-5D quartiles were –4.2 (adjusted P = 0.0050), –2.6 (adjusted P = 0.0476), and –2.4 (adjusted P = 0.0298), respectively, which were lower than the –0.1 of the reference 4th quartile. Conclusions: HRQOL as assessed by EQ-5D is associated with longitudinal cognitive decline in frail elderly people, and cognitive function may be maintained in individuals with high HRQOL levels.