Abstract
Purpose: :
To investigate the relationship between functional ability and depressed mood among visually impaired patients.
Methods: :
The 15-item Geriatric Depression Scale (GDS) and the adaptive 460-item Activity Inventory (AI) questionnaires were administered by telephone prior to rehabilitation to 936 patients across 27 collaborating clinical low vision rehabilitation centers within the US. Patients ranged in age from 18 to 98 years with a median age of 77. 66% of patients were female. Habitual mean log MAR visual acuity was 0.61 (Snellen 20/82) in the better eye with 36% of patients having visual acuity >20/60 and 38% <20/60 to >20/200. The majority of patients (54%) had macular disease with 29% of all patients having atrophic macular degeneration.
Results: :
Separate Rasch analyses were performed on patient responses to the GDS and to the AI. There is a moderate correlation of -0.33 between depressed mood and functional ability (p<.001). There is no evidence of depression-related differential item functioning (DIF) in the AI responses. There also is no evidence of depression-related changes in AI response category thresholds. Between-patient variance in functional ability is constant with respect to depressed mood, however between-patient variance in depressed mood increases as functional ability declines. Using the usual criterion score on the GDS for depressed mood, the prevalence rate of depressed mood increases from 3% at the highest levels of functional ability to an asymptotic value of 25% as functional ability declines.
Conclusions: :
The risk of depression among visually impaired patients increases as overall functional ability declines. Despite the moderate correlation, depressed mood and functional ability are independent factors and the majority of visually impaired patients are not depressed. The results support the hypothesis that stress associated with higher levels of disability place individuals at greater risk of depression.
Keywords: low vision • clinical (human) or epidemiologic studies: risk factor assessment • clinical (human) or epidemiologic studies: prevalence/incidence