Brain cells die quickly if their oxygen supply is cut off.
Brain atrophy means the brain matter has shrunk, often because brain cells are dying or dead.
Brain atrophy is caused by lack of oxygen.
what causes brain atrophy?

a) Smoking
b) sodium
c) Dehydration
d) sweating
e) death
f) birth
g) Veins and arteries.
h) lack of oxygen