Synergistic Impact of Visual and Cognitive Impairments on Health-related Quality of Life in a Multi-Ethnic Asian Population

Introduction: The concomitant impact of visual impairment (VI) and cognitive impairment (CI) on health-related quality of life (HRQoL) in older adults is unclear. We aimed to determine the synergistic effect of baseline VI and CI on HRQoL decline at 6 years in multiethnic Asians.Methods: We included Chinese, Malay, and Indian adults aged >= 60 years who participated in baseline (2004-2011) and 6-year (2011-2017) follow-up visits of the Singapore Epidemiology of Eye Diseases Study, a population-based cohort study in Singapore. Visual acuity (VA) was objectively measured at both visits, with VI defined as presenting VA >0.3 LogMAR in the better eye. CI was defined as Abbreviated-Mental-Test scores of <= 6 and <= 8 for individuals with <= 6 and >6 years of formal education, respectively. HRQoL was measured using the European Quality of Life-5 Dimensions (EQ-5D) questionnaire. HRQoL decline was defined as the difference in the composite EQ-5D scores at baseline and 6-year follow-up and deemed clinically meaningful if the reduction was equal to or larger than the minimal clinically important difference (MCID). Multivariable linear regression assessed the independent associations and synergism (beta-interaction) between baseline VI and CI on EQ-5D decline.Results: Of the 2,433 participants (mean (SD) age: 67.6 (5.5)) at baseline, 559, 120, and 151 had VI only, CI only, and both impairments, respectively. HRQoL decline in individuals with baseline comorbid VI-CI was clinically meaningful and was 2.0 times (beta = -0.044, 95% confidence interval: -0.077 to -0.010) and 3.7 times (beta = -0.065, 95% confidence interval: -0.11 to -0.022) larger than those with VI only and CI only, respectively. Importantly, there was a significant synergism (beta-interaction = -0.048, 95% confidence interval: -0.095 to -0.001) between baseline VI and CI as predictors of HRQoL decline, suggesting that individuals having both conditions concurrently had a greater HRQoL reduction than the sum in those with VI alone and CI alone. The affected HRQoL domains included mobility and usual activities. Conclusions: Concomitant VI-CI potentiated HRQoL decline to a greater extent than the sum of individual contributions of VI and CI, suggesting synergism. Our results suggest that rehabilitative interventions such as the use of mobility aids and occupational therapy are needed to maintain HRQoL in older adults with concomitant VI-CI. Moreover, preventive interventions targeting at early detection and management of both VI and CI may also be beneficial.