Dissecting Microscopes

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 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.

This study is conducted to determine the effect of different kinds of bone substitutes and collagen on the concentration of platelet-derived growth factor (PDGF) and transforming growth factor β-1 (TGF β-1) in platelet-rich plasma (PRP). PRP is treated with thrombin, hydroxyapatite (HA), and thrombin, HA alone, collagen-grafted HA, calcium metaphosphate (CMP), and collagen-grafted CMP. The concentrations of PDGF-AB and TGF β-1 are measured. After PRP treated with HA and CMP, the concentrations of PDGF and TGF β-1 are not significantly different from the concentration of them in PRP alone. The concentrations of PDGF in PRP with collagen-grafted HA and collagen-grafted CMP are significantly higher than that of PRP with HA and CMP. The concentrations of PDGF and TGF β-1 in PRP with collagen-grafted CMP are higher than with collagen-grafted HA. The results of multiple regression analysis show that PDGF increased with the use of collagen and thrombin, and is higher in native whole blood with higher platelet counts. However, PDGF decreased with the use of HA. In conclusion, HA and CMP do not seem to be able to activate platelets by themselves. However, if they had collagen grafted onto them, they could activate platelets and release growth factors.