longer and longerAs a result的意思是“结果……”，所以越来越多的中年人必须照顾年迈的父母的原因就是As a result前面的"People are living longer and longer．”

People are living longer and longer. As a result, more and more middle-aged adults have to take care of their ageing parents. When your parents can no longer care for themselves, these adults may be forced to stay at home to care for them. Taking care of ageing parents is quite difficult. For example, an ageing parent may become blind, He or she needs children to perform a lot of everyday work. The roles of parents and children are then changed. Children are forced to care for their parents as if their parents were children. When children find it difficult to take care of their dependent parents, they often decide to take them to a nursing home. There, proper care and attention can be given. This allows the children to return to their normal everyday life.