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.
Sixty-three years later the U.S. Census Bureau released its projection for growth in the 21st century. The âmiddle seriesâ â the most likely scenario â showed a population of about 394 million residents in 2050. That projection was shown by the results of the 2000 Census to be already understated.