Past, Present, and Future of Healthy Life Expectancy.

The success of the current biomedical paradigm based on a "disease model" may be limited in the future because of large number of comorbidities inflicting older people. In recent years, there has been growing empirical evidence, based on animal models, suggesting that the aging process could be delayed and that this process may lead to increases in life expectancy accompanied by improvements in health at older ages. In this review, we explore past, present, and future prospects of healthy life expectancy and examine whether increases in average length of life associated with delayed aging link with additional years lived disability-free at older ages. Trends in healthy life expectancy suggest improvements among older people in the United States, although younger cohorts appear to be reaching old age with increasing levels of frailty and disability. Trends in health risk factors, such as obesity and smoking, show worrisome signs of negative impacts on adult health and mortality in the near future. However, results based on a simulation model of delayed aging in humans indicate that it has the potential to increase not only the length of life but also the fraction and number of years spent disability-free at older ages. Delayed aging would likely come with additional aggregate costs. These costs could be offset if delayed aging is widely applied and people are willing to convert their greater healthiness into more years of work.