35 years: Hair and vision loss
Some of the first tell-tale signs that you're getting old. Fight the good fight with Rogaine, large-print books, and denial while you still can.
40 years: An extra 20lb
If you gain an average of 1lb a year after high school, now's the time you look in the mirror and say, "Where the hell did these 20lb come from?" The answer is: a desk job, stress, fast and processed foods, an unused gym membership, and probably 20 or 30 other contributing factors.
The weight gain alone may or may not be something you're worried about (hey, who doesn't like a little extra cushion for the pushin'?), but that 20lb could signify other health problems. Hit the doctor's office stat for blood work and blood pressure readings. It's better to head major problems off now than wait another 20 years (and 20lb).