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.
âAccording to the US statistics, the US lost not less than 8 million 553 thousand people from 1931 to 1940. Afterwards, population growth indices change twice instantly exactly between 1930-1931: the indices drop and stay on the same level for ten years.