Common features of brain disorders that get worse over time include:

1. Loss of Neurons: When people are diagnosed with Alzheimer's, about 20% of brain cells, or neurons, are already lost.

2. Protein Buildup:

   • In Alzheimer's, sticky clusters called amyloid-beta plaques can affect 60-80% of the brain.
   • In Parkinson's, there are clumps known as Lewy bodies that have a protein called alpha-synuclein inside them.

3. Inflammation in the Brain: In these disorders, about 60% of the affected neurons show signs of inflammation from tiny immune cells called microglia.

4. Problems with Brain Signals: Changes in how neurons communicate can cause memory and thinking issues in Alzheimer's. There can be a decline of 30-40% in markers that show how well neurons are connecting.

5. Reduced Brain Chemicals: In Parkinson's, there’s a significant loss of dopamine-producing neurons. This can lead to a drop of 60-70% in dopamine, which is an important brain chemical that helps with movement and coordination.