Oxidative Protein Damage Is Associated With Severe Functional Dependence Among the Elderly Population: A Principal Component Analysis Approach

Studies of the role of oxidative stress in functional dependence among the aging population are limited. In this report, we address this situation through an analysis of a large panel of blood oxidative biomarkers in elderly population. Because the analysis of multiple biomarkers increases the complexity of data interpretation, this investigation has utilized both an analysis of single biomarkers in addition to employment of the statistical data reduction tool principal component analysis that might allow for a clearer description of redox status as compared with a single measure alone. We studied three groups of participants older than 65 years based on their Barthel Index: an independent group (100-95), a moderately dependent group (94-60), and a severely dependent group (59-0). We observed a significant increase in circulating protein carbonyl levels in the severely dependent group as compared with the independent and moderately dependent groups. Using principal component analysis, we found at least three factors (an erythrocyte-related component, a protein damage-related component, and a plasma-related component) that could be used to assess the different oxidative parameters in our population. We discovered a significant association of higher levels of the protein damage-related component with the severely dependent group. Protein damage levels could be assessed in clinical use as a biomarker of severe dependence. Furthermore, our results support the hypothesis that functional decline could be associated in part due to oxidative stress. Finally, we show that principal component analysis could be a useful statistical tool in the analysis of age-related decline.