Extreme sleep deprived for 4+ years. heard it kills brain cells. i'm 18, any hope i can regrow them and recover?

Yes: Sleep is important and will affect your body over the long term. Night shift work does take its toll. If the sleep deprived state is because you can't sleep there are many diagnosis and treatments. Some sleep study labs specialize in diagnosing the problem. Start with your PCP, get a physical and labs. You then are on your way to better sleep and feeling healthy again.