Ageing is a natural process. In our lifetime we go through transition from growing and developing into decline and damage at the cellular level.
The brain starts shrinking and losing connectivity among axons, dendrites and synapses at a very slow pace from age 30 and later rapidly at a later stage of life. However, the brain can grow back new nerve cells.
Ageing is not a health condition it is a part of the development process. If necessary modifications are made in the way of living as per the needs of the body, a healthy old age can be lived. Nutritious diet, good sleep, mind and body exercise, socially balanced active life are steps towards healthy ageing.