can a person’s IQ degrade ?

As far as i come to understand the brain and the mind i think it will tend to degrade.
To put in simple terms,
the brain is but a machine.
If not used properly it will tend to lose its functionality.
Intelligence Quotient is your capacity to apply whatever u has learnt.
And to apply more, you got to learn more
you can’t just piggy back on the first 15-20 years of your life when you worked hard.
You got to learn and grow every day.
U got to evolve everyday with changing times.

Let me quote one of my favorite personalities,
Dr. Philip Kolter,

" today, you got to move faster
to stay at the same place. "

The fact of the matter really is that IQ is just as assessment of your capacity to use your knowledge at a particular point in time, at a certain age, with your specific knowledge, given a defined set of how the world is.

It is however important again to understand that nothing is constant
everything is changing constantly and rapidly.
To even keep your IQ score at a particular number you got to work harder.
Therefore degrading IQ score is only obvious given the nature of how the mind works
however, having a good IQ score would mean you being at a better position to maintain that score and keep improving.