What you
may have some control over:
Alzheimer's disease, atherosclerosis, asthma, cancer, chronic liver disease or cirrhosis, Chronic Obstructive Pulmonary Disease, Type 2 diabetes, heart disease, metabolic syndrome, nephritis or chronic renal failure, osteoporosis, acne, stroke, depression and obesity.
Some commenters maintain a distinction between diseases of longevity, and diseases of civilization.
Drug abuse, especially tobacco smoking and alcohol drinking, as well as the lack of exercise may increase the risk of certain diseases in later life.
In 1900, the top three causes of death in the United States were pneumonia/influenza, tuberculosis, and diarrhea/enteritis.
[they ate pretty naturally and weren't very sedentary back then].
http://en.wikipedia.org/wiki/Lifestyle_diseases