No... Its not the weight gain around the midriff or the beginning of wrinkles, or the greying of hair (everywhere) or the weakening eyesight that is the worst part of growing older...
What pains me most is people you've known and loved, who were older than you, and now older even more, kicking the bucket and leaving you with memories and nothing more.
Aunts, uncles, grandparents, teachers, even icons (MJ, Prince, Whitney Houston etc.)...people you'd thought would be around just because they always were.
Death is inevitable but when it become a deluge, thats when you know that it is also an indication of your own ageing. I remember my dad calling me many years ago (when he was my age), shaken up after a friend of his died of a cardiac arrest in his office - all he said was, "Its begun."
I didn't understand it then, but I do now.