Inflammatory markers provide invaluable tools for studying health and disease across the lifespan. Inflammation is central to the immune system’s response to infection and wounding; it also can increase in response to psychosocial stress. In addition, depression and physical symptoms such as pain and poor sleep can promote inflammation and, because these factors fuel each other, all contribute synergistically to rising inflammation. With increasing age, persistent exposure to pathogens and stress can induce a chronic proinflammatory state, a process known as inflamm-aging. Inflammation’s relevance spans the life course, from childhood to adulthood to death. Infection-related inflammation and stress in childhood, and even maternal stress during pregnancy, may presage heightened inflammation and poor health in adulthood. In turn, chronically heightened inflammation in adulthood can foreshadow frailty, functional decline, and the onset of inflammatory diseases in older age. The most commonly measured inflammatory markers include C-reactive protein (CRP) and proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). These biomarkers are typically measured in serum or plasma through blood draw, which capture current circulating levels of inflammation. Dried blood spots offer a newer, sometimes less expensive collection method but can capture only a limited subset of markers. Due to its notable confounds, salivary sampling cannot be recommended. Inflammatory markers can be added to a wide range of lifespan developmental designs. Incorporating even a single inflammatory assessment to an existing longitudinal study can allow researchers to examine how developmental profiles and inflammatory status are linked, but repeated assessments must be used to draw conclusions about the associations’ temporal order and developmental changes. Although the various inflammatory indices can fluctuate from day to day, ecological momentary assessment and longitudinal burst studies have not yet incorporated daily inflammation measurement; this represents a promising avenue for future research. In conclusion, mounting evidence suggests that inflammation affects health and disease across the lifespan and can help to capture how stress “gets under the skin.” Incorporating inflammatory biomarkers into developmental studies stands to enhance our understanding of both inflammation and lifespan development.
Stephanie J. Wilson, Alex Woody, and Janice K. Kiecolt-Glaser
Carolyn M. Aldwin and Ritwik Nath
Erythocyte sedimentation rate (ESR) is one of the oldest measures of inflammation. It is used extensively in clinical medicine and has shown some utility in biomedical research. It is a nonspecific inflammation assay, and although it is less sensitive than more modern measures such as C-reactive protein, it is a useful measure in chronic illnesses. In general, ESR increases with age and appears to be a biomarker of aging in general. It predicts both cardiovascular disease (CVD) and cancer and is elevated in autoimmune disorders such as rheumatoid arthritis. Further, it predicts mortality both in the general population and in those with chronic illnesses such as CVD and cancer, independent of other indicators of illness severity. Interestingly, ESR is not associated with anxiety or general measures of distress but is consistently associated with measures of depression and suicidal ideation. Further, the effect of depressive symptoms on mortality appears to be mediated through increases in ESR. Studies of the relationship between stress and ESR have been less consistent, primarily because early studies were largely cross-sectional and in small samples. Studies using more modern, longitudinal analyses in larger samples may show more consistent results, especially if multilevel modeling was used that examined within-person changes in ESR in response to stress. Given that other large, longitudinal studies, such as the Baltimore Longitudinal Study on Aging, the Rotterdam Study, The Reykjavik Cohort Study, and Women’s Healthy Ageing Study have included ESR in their biomedical assays, it should be possible to analyze existing data to examine how psychosocial factors influence inflamm-aging in humans.
Chun-Jung Huang, Matthew J. McAllister, and Aaron L. Slusher
Psychological stress disorders, such as depression and chronic anxiety contribute to increased risk of cardiovascular disease and mortality. Acute psychological and physical stress exacerbate the activity of sympathetic-adrenal-medullary system, resulting in the elevation of cardiovascular responses (i.e., heart rate and blood pressure), along with augmented inflammation and oxidative stress as major causes of endothelial and metabolic dysfunction. The potential health benefits of regular physical activity mitigate excessive inflammation and oxidative stress. Along with physical exercise, complementary interventions, such as dietary modification are needed to enhance exercise effectiveness in improving these outcomes. Specifically, dietary modification reduces sympathetic nervous system activity, improve mitochondrial redox function, and minimize oxidative stress as well as chronic inflammation.
Conscience P. Bwiza, Jyung Mean Son, and Changhan Lee
Aging is a progressive process with multiple biological processes collectively deteriorating with time, ultimately causing loss of physiological functions necessary for survival and reproduction. It is also thought to have a strong evolutionary basis, largely resulting from the lack of selection force. Here, we discuss the evolutionary aspects of aging and a selection of theories founded on a variety of biological functions that have been shown to be involved in aging in multiple model organisms, ranging from the simple yeast, worms, flies, killifish, and rodents, to non-human primates and humans. The conglomerate of distinct theories has together revolutionized aging research in the past several decades, far more than what humankind has known since the dawn of civilization. However, not one theory alone can independently explain aging and should not be interpreted out of context of the cell and organism in its entirety. That said, the 21st century has been and will be an exciting time in the field of aging, with scientific advances on health span and lifespan being made at multiple fronts of biology and medicine in an unprecedented scale.