In order to qualify for disability you are going to need current documentation on the specific disabilities that prevent you from working. They are not going to take your word for it. So you need a lot of documentation from reputable sources. Something from 18 years ago can be included but will not in and of itself allow you to qualify, if you have worked in the last 18 years, they will want proof that you have deteriorated to the point you can no longer work. So you will need to get to the doc and if they agree you can not work, and are willing to report on that, you can start the process. If you do not do that you set yourself up to be denied.