why do disease such as parkinson’s etc, nearly almost present themselves in older people?

Question: why do disease such as parkinson's etc, nearly almost present themselves in older people?
- Keywords:
  ageing,
  alzheimers,
  disability,
  disease,
  illness,
  older people,
  parkinsons
Asked by sheeana to Ollie, Georgia, Amy on 15 Jun 2011.
- Amy Reeve answered on 15 Jun 2011:
  
  Good question…. what do you think?
  
  A lot of the theories we have for what causes these diseases are based on cells accumulating damage. In the case of Parkinson’s disease this damage causes a build up of protein, the mitochondria to stop working (in this case the damage is mutations in mitochondrial DNA) and the cells stop being able to communicate with each other properly. All this damage however takes a life time to build up which is why these disease affect the elderly. The question is why don’t they affect every old person………? 🙂

Question: why do disease such as parkinson's etc, nearly almost present themselves in older people?