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Testosterone and Aging: Clinical Research Directions
sidered in study design and conduct. More specifically, the committee was asked to review and consider:
epidemiologic data on normal levels of testosterone during the lifespan and the associations with morbidity and mortality;
the risks and benefits of testosterone therapy;
the potential public health impact of testosterone therapy in the United States; and
the ethical issues related to the conduct of clinical trials of testosterone therapy.
The committee members included experts from many fields including bioethics, endocrinology, internal medicine, urology, oncology, epidemiology, biostatistics, clinical trials research, geriatrics, and behavioral science. The committee held four meetings over the course of the 12-month study and convened a public scientific workshop in Phoenix, Arizona, on March 31, 2003.
AGING AND HORMONAL CHANGES
Increases in life expectancy are resulting in an aging global and U.S. population. In 1900, persons age 65 years and older accounted for only 4 percent of the U.S. population. By 2000, that proportion had risen to 12.4 percent, or 35 million people, and it is projected to rise to 19.6 percent, or 71 million people, by 2030 (CDC, 2003). It has been noted that of all the people who have ever lived to the age of 65 years, more than half are now alive (Resnick, 2001).
The oldest age group—those over age 85—are the fastest growing segment of the older population. It is estimated that the number of persons age 80 and older will increase from 9.3 million in 2000 to 19.5 million in 2030 (CDC, 2003). The ratio of older men to women will narrow slightly over the next few decades in the United States. Men represented 41 percent of those over age 65 in 2000; by 2030 that percentage is projected to increase to 44 percent (CDC, 2003).
Life expectancy continues to rise as well. Male life expectancy at birth in the United States reached a record 74.4 years in 2001 (Arias and Smith, 2003). The growing number of older individuals increases demands on public health and medical and social services. Chronic diseases disproportionately affect older people, who are also more prone to frailty and disabilities (CDC, 2003). In addition, many older people have sensory, mobility, and cognitive impairments that affect their quality of life and may predispose them to falls, injuries, and fractures. In the United States,