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. Census Bureau expects the U.S.A. population to grow to reach these estimates over the next few decades: 1  2010 - 307,745,538. 2  2020 - 336,031,546. 3  2030 - 363,811,435. 4  2040 - 392,172,658. 5  2043 - 400,527,776 (the year of 400 million)