Assessment of the effect of visual impairment on mortality through multiple health pathways: structural equation modeling.
OBJECTIVE
To estimate the direct effects of self-reported visual impairment (VI) on health, disability, and mortality and to estimate the indirect effects of VI on mortality through health and disability mediators.


METHODS
The National Health Interview Survey (NHIS) is a population-based annual survey designed to be representative of the U.S. civilian noninstitutionalized population. The National Death Index of 135,581 NHIS adult participants, 18 years of age and older, from 1986 to 1996 provided the mortality linkage through 2002. A generalized linear structural equation model (GSEM) with latent variable was used to estimate the results of a system of equations with various outcomes. Standard errors and test statistics were corrected for weighting, clustering, and stratification.


RESULTS
VI affects mortality, when direct adjustment was made for the covariates. Severe VI increases the hazard rate by a factor of 1.28 (95% CI: 1.07-1.53) compared with no VI, and some VI increases the hazard by a factor of 1.13 (95% CI: 1.07-1.20). VI also affects mortality indirectly through self-rated health and disability. The total effects (direct effects plus mediated effects) on the hazard of mortality of severe VI and some VI relative to no VI are hazard ratio (HR) 1.54 (95% CI: 1.28-1.86) and HR 1.23 (95% CI: 1.16-1.31), respectively.


CONCLUSIONS
In addition to the direct link between VI and mortality, the effects of VI on general health and disability contribute to an increased risk of death. Ignoring the latter may lead to an underestimation of the substantive impact of VI on mortality.
Christ
Sharon L
SL
Odum Institute, University of North Carolina, Chapel Hill, North Carolina 27599-3355, USA. slchrist@email.unc.edu
Lee
David J
DJ
Lam
Byron L
BL
Zheng
D Diane
DD
Arheart
Kristopher L
KL
D000328:Adult; 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; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014786:Vision Disorders / Q000401:mortality*; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*