The answer is no, not really. Any one can change their career and you must try not to think that you are too old. If you want to be a doctor for example, then you will have to bear in mind how much studying and training you will have to do, so if you are already in your 50’s you may wonder if it is worth the time as you may not have much time once you have graduated to actually follow your career path.
One of the main things that holds people back from studying for a new career when they are older is money. Unless you can find a job which offers training whilst you work, you may have to go in to full time studies and lose out on an income for a number of years. This can put a lot of financial strain on an individual.
IF you are able to, you may consider doing an evening course at college or an Open University course so you can still keep working full time. This is very hard work and you will have to be extremely disciplined in order to manage both effectively.