Biological Aspects of Health: Validating, Analyzing, and Profiling Cytokines in Older U.S. Adults

Increases in life expectancy and advances in medical fields have led to an upsurge in the number of people that live into old age. This and the corresponding increase in age-related diseases has not yet been met with an appropriate amount of research. In fact, little is known about the biological, psychological, and social changes that accompany aging. In an attempt to narrow this gap, The National Social Life, Health, and Aging Project (NSHAP) was initiated in 2005 to examine the relationship between health, social support, and sexuality in aging Americans. In addition to survey data, this study collects several biomarkers indicative of health. Using this data, the aim of my dissertation is extensive. First, I show that sex based discrepancies in cardiovascular disease diagnosis and treatment extend into older age, which internally validates the NSHAP data. Next, I reveal that these discrepancies are not accompanied by differences in traditional biomarkers of inflammation as would be expected. Then, I discuss how we developed and validated our measurement of cytokines, which are protein molecules with interactive and cascade effects that regulate immune processes, to examine physical and mental health status by means of immune functionality. The sheer number of cytokines and their numerous possible interactions makes studying their roles in health necessarily complex. Further, little is known about the distribution of individual cytokines or cytokine profiles among healthy older adults. In 2010-11, NSHAP introduced an innovative protocol for obtaining plasma samples in the home and used them to measure 22 cytokines. I describe the univariate and joint distributions of cytokines among U.S. older adults, multivariate methods for analyzing multiple analytes within individuals that address both challenging measurement issues and possibly non-linear and discrete relationships, and use these methods to study the association between inflammatory profiles and health conditions related to immune processes. Ultimately, I show that cytokine levels are a reliable and specific indicator of immune function and health status in a population-based study of older adults.