disabling conditions now survive longer into adulthood. Numerous important chronic diseases still have no known or controllable causes and continue unabated, such as mental illnesses, chronic skin conditions, inflammatory bowel diseases, collagen vascular diseases, and degenerative neurological illnesses. Chronic illnesses resulting from injuries or burns or from infectious agents (e.g., hepatitis B and C, HIV, H. pylori) also continue to take an important long-term toll on those affected. The control of many chronic illnesses among young and middle-aged adults, even with some important successes, has delayed the onset of these illnesses to older ages. Amid medical progress, enhanced population survival has also permitted the emergence of more degenerative illnesses at older ages, such as arthritis, dementia, and end-stage kidney disease. Moreover, the availability and application of more intensive medical therapies has increased treatment costs and the probability of adverse events. Some examples include deep vein thrombosis following joint replacement surgery for hip or knee arthritis; increases in type 2 diabetes during treatment with some common mental health medications; more cardiovascular events with intensive glucose lowering in some patients with diabetes; antibiotic resistant infections of kidney dialysis catheters; and increased risk of falls or fractures among frail elders treated with sedative-hypotic medications intended for improving sleep or reducing agitation.
In addition, some population risk factors for chronic diseases are going in the wrong direction. Obesity levels have increased dramatically, along with physical inactivity and unhealthful eating, accounting for a considerable proportion of prevalent chronic diseases, such as diabetes and cardiovascular diseases (McGinnis and Foege, 1993; Mokdad et al., 2004). As a result, the average life expectancy for Americans living in most U.S. counties has decreased over the past decade relative to gains being made in other leading nations around the world (Kulkarni et al., 2011). Thus, in the modern era, the toll of chronic diseases on physical, mental, and social health, health care, and the economy continues to a problem of critical magnitude in America today (Center for Healthcare Research and Transformation, 2010; DeVol and Bedroussian, 2007; Michaud et al., 2006; NCCDPHP, 2009).
Taking a population health perspective means considering the magnitude and distribution of health outcomes from the viewpoint of societal groups or populations (Kindig, 2007). From such a perspective, genes, biology, behavior, and environment are all seen to interact in their impact on health and function. Older adults are biologically prone to being in poorer health than adolescents because of the physical and cognitive effects