For brain health, it's not really the number of brain cells you have as much as their health and quality - and the number of connections between them - that matters. What you learn, and how you learn, will positively affect your brain health by increasing the number of connections between the cells.
There are mental faculties that we can expect to decline with age:
- Remembering people's names
- Recalling facts and words
- Recalling where they heard something and/or who told them
- Remembering the location of household objects
- Recalling events from recent past
- The ability to multitask
- Reaction time
But there are things that do not have to decline with age:
- Vocabulary
- Decision-making
- Creativity
- Ability to learn
- Word generation - being fluent and able to use language
- Paired associate learning - a test of how well new info is remembered
It is important that you take seriously any signs of declining mental faculties, even if it's something that can be attributed to age. If you start to forget names, for example, make a serious effort to learn and remember them in the future. Do not allow the problem to slip and get worse. Make the most of the skills that are retained and even improve as you age!
"I have a fantastic memory: Even elephants consult me".
~ Noel Coward