Direct and indirect effects of visual impairment on mortality risk in older persons.
OBJECTIVE
To investigate pathways from visual impairment to increased all-cause mortality in older persons.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Karpa
Michael J
MJ
Centre for Vision Research, Department of Ophthalmology, and Westmead Millennium Institute, Australia.
Mitchell
Paul
P
Beath
Ken
K
Rochtchina
Elena
E
Cumming
Robert G
RG
Wang
Jie Jin
JJ
D000368:Aged; D002423:Cause of Death; D004185:Disability Evaluation; D005260:Female; D006302:Health Services Research; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009517:New South Wales / Q000453:epidemiology; D012307:Risk Factors; D014786:Vision Disorders / Q000401:mortality*; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*