In one study scientists compared the health status of 386 men and women who took surveys in 1968 when they were 50 years old. Those with the most negative stereotypes about older people were much more likely to have had strokes or heart attacks than those with more positive views.
The good news is that attitudes about aging are not set in stone, it appears they can be changed, especially if people are exposed to positive role models.
So think positive! You're only as old as you feel.