Assessment of the Effect of Visual Impairment on Mortality through Multiple Health Pathways Using Structural Equation Modeling
Sharon L Christ 1*,
David J Lee 2,
Byron Lam 3,
Diane Zheng 2,
and
Kristopher Arheart 2
1 Chapel Hill Odum Institute, University of North Carolina, Chapel Hill, North Carolina, United States
2 Epidemiology and Public Health, University of Miami Miller School of Medicine, Miami, Florida, United States
3 Bascom Palmer Eye Institute, Miami, Florida, United States
* To whom correspondence should be addressed. E-mail: slchrist{at}email.unc.edu.
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Abstract |
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Purpose: 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 US civilian non-institutionalized population. The National Death Index of 135,581 NHIS adult participants, aged 18 years and older, from 1986 to 1996 provided the mortality linkage through 2002. A generalized linear structural equation with latent variable model (GSEM) is used to estimate a system of equations with various outcomes. Standard errors and test statistics are corrected for weighting, clustering, and stratification.
Results: VI affects mortality directly controlling for the covariates. Severe VI increases the hazard rate by a factor of 1.28 [95% CI:1.07,1.53] compared to 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 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 visual impairment and mortality, the effects of visual impairment 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.
Key Words:
visual impairment, mortality, adult, disability, self-rated health
