I am assuming you are talking about a certain country or region (India?) where only 8% of the population is 45+. This means that the average life expectancy is relatively low (compare that to North America or Western Europe) and 45 years is a fairly advanced age. If you've reached advanced age for your country/region, there is a high probability (on average) that you'll die fairly soon. Since mitosis does not stop until about 115 years of age, only a serious disease can end your life, meanwhile you'll consume a large chunk of medicare fighting it. So there is nothing vulnerable about forties; 45+ is just an average number for this country/region. And people in the 45+ category consume a large chunk of medicare simply because in this country/region anyone who is 45+ is (on average) already rather old and prone to sickness.