9.Declines in Hormone Levels
úHormone levels run down with age and so do all of the body systems they regulate
10.Susceptibility to Cancers
úRisk of cell cancer pathology due to shift in gene expression increases radically with aging
11.Susceptibility to Cardiovascular Disease 
úCardiovascular diseases are the biggest killers of old people
Major theories of aging
To see details click on title of theory