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Dandan Diane Zheng, Sharon L Christ, Byron L Lam, Stacey Tannenbaum, David J Lee, University of Miami Ocular Epidemiology Group; Visual Acuity and Increased Mortality: The Role of Allostatic Load and Functional Status. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2683.
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Poor vision can have a detrimental impact on functional status and may have an effect on allostatic load (AL). AL is a measure of the cumulative physiological wear and tear on the body's regulatory systems. In the present study, we examined the relationship between vision, functional status, allostatic load, and mortality by estimating the direct and indirect effects of visual acuity (VA) on mortality through functional status and allostatic load in older adults.
Data from 4,981 adult participants (> age 60 years) of the 1999-2004 National Health and Nutrition Examination Survey (NHANES) with mortality linkage through 2006 were analyzed. Functional status was assessed by Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL). The AL index is comprised of 10 biomarkers and anthropometric measures based on the scientific literature. VA was treated as a four category ordinal variable with categories no VI, mild VI, moderate VI, and severe VI. Structural equation modeling was employed using three mediating variables representing ADL, IADL and AL to examine the effects of VA on all-cause mortality (Model depicted in Figure).
VA increases the risk of mortality directly after adjusting for ADL, IADL, AL and other covariates. A one unit change in VA category increased the risk of mortality by 1.17; 95% CI: [1.05, 1.32]. IADL and AL both predict mortality (HR=1.15 [1.10, 1.20] and HR=1.13 [1.06, 1.20] respectively). ADL did not predict mortality after controlling for IADL, AL and other covariates (HR=0.98 [0.91, 1.05]). Worse VA was associated with increased AL (b= 0.11; p=0.013) and worse IADL (b=1.06; p<0.001). VA increases mortality risk indirectly through IADL (HR= 1.07 [1.03, 1.12]) and AL (HR=1.11; [1.06, 1.17]). The total effect of VI on mortality including its influence through IADL and AL is HR 1.27 [1.12, 1.44].
Visual impairment directly increases the risk of mortality and may indirectly increase mortality risk slightly through its adverse impact on functioning status IADL and on Allostatic Load.
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