Direct and Indirect Effects of Visual Impairment on Mortality Risk in Older Persons

Abstract

To investigate pathways from visual impairment to increased all-cause mortality in older persons. The Blue Mountains Eye Study examined 3654 persons 49 years and older (82.4% response) during 1992-1994 and after 5 and 10 years. Australian National Death Index data confirmed deaths until 2005. Visual impairment was defined as presenting, correctable, and noncorrectable, using better-eye visual acuity. Associations between visual impairment and mortality risk were estimated using Cox regression and structural equation modeling. After 13 years, 1273 participants had died. Adjusting for mortality risk markers, higher mortality was associated with noncorrectable visual impairment (hazard ratio [HR], 1.35; 95% confidence interval [CI], 1.04-1.75). This association was stronger for ages younger than 75 years (HR, 2.58; 95% CI, 1.42-4.69). Structural equation modeling revealed greater effects of noncorrectable visual impairment on mortality risk (HR, 5.25; 95% CI, 1.97-14.01 for baseline ages <75 years), with both direct (HR, 2.16; 95% CI, 1.11-4.23) and indirect (HR, 2.43; 95% CI, 1.17-5.03) effects. Of mortality risk markers examined, only disability in walking demonstrated a significant indirect pathway for the link between visual impairment and mortality. Visual impairment predicted mortality by both direct and indirect pathways, particularly for persons younger than 75 years with noncorrectable visual impairment. Disability in walking, which can substantially influence general health, represented a major indirect pathway.