I don't need to be reminded how I'm one year closer to dying / osteoporosis / arthritis and a ton of other age-related issues.
Since you prefer to look at things this way, let me point out that you are "closer to dying" etc. with every passing moment. You don't magically jump one year closer to your death on one specific day of the year.
Your "birthday" is of no biological significance, it is of social significance. Wishing someone on their birthday (or wedding anniversary, etc.) gives people a reason (excuse, if you prefer) to socialize without appearing creepy or awkward.
Getting wished doesn't really cause you any harm once you stop being upset about it, and it makes them happy for wishing you, so what's the problem?
Complaining about people following a (mostly) harmless convention will label you as a ... let's just say, strange person, and people will avoid approaching you over non-birthday related topics as well. This is especially problematic in the workplace where you (usually) have to work together with others, and even worse, if you are in a supervisory role.
Hence, if someone wishes you on your birthday, simply accept it gracefully, politely point out that you don't do these celebrations, and continue to have some small talk if you wish. You don't need to give any reasons. Something like the following should be good enough:
Thanks for your wishes. I am not much into these birthday celebrations though. Hey, by the way, did you watch ... last night?
Then forget about it and move on.
Worrying about trivial and unimportant problems will take you closer to your death. :-)
Personal anecdote: I am atheist, people wish me on Christmas, Eid, and many other religious events, some of which I don't even know about. I simply thank them, have some small talk, and move back to my work. Giving them a long lecture on atheism will (1) waste my time, (2) kill their enthusiasm, and (3) give me the reputation of being a "jerk", none of which helps me.