I have been practising Jiu-Jitsu for a few years now and being over 40 years old, I have learned a few hard lessons. The beauty of Jiu-Jitsu that anyone can practice it no matter what your age is, or your physical limitations, or even mental illnesses. There are things we have to consider though if we wish to embark on this lifestyle that is the life of a Jiu-Jitsu practitioner.
Age along with physical limitations (such as injuries) can slow down our progress, but not necessary that it becomes a detriment to our growth in this art. As with every sport/martial art, we have our own different pace of growth.