Introduction. Beta-blockers, also known as beta-adrenoceptor blocking agents, are medications used to treat conditions such as angina, heart failure and high blood pressure. They decrease the activity of the heart by blocking the action of hormones like adrenaline.
1 The concept of âdemographic changeâ describes a populationâs age structure adjusting to. changes in living conditions. Consequently, changes in thcomposition of a societyâe s age. structure are the result of social shifts. (. 2  cf. . 3  theory of first and second demographic transition.
The U.S. population doubled during the past 60 years from 135 million to more than 270 million (NGS, 1995) and, based on the current U.S. growth rate of approximately 1% per year (USBC, 1996), is projected to double again to 540 million in the next 70 years.