Masters runner here, 60s and running 62 for 10 miles this past year, so in relatively decent fitness but not anywhere near the very top. I have had lifelong asthma mostly as a kid but it came back in my 30s. Had a couple ER visits as a kid and one as an adult (after doing V02 workout at 2F). No TUE needed for albuterol, but it's not a performance "enhancer" especially at low doses. I take two puffs 20 minutes before a hard workout or some races (not the 23 in a day as Rupp et al. were purported to use). Other than that a couple cups of tea or coffee and ibuprofen as needed.
I travel some to big races and know many top age group racers age 45 and up. Contrary to what is said in this thread, doubt that it is super wide-spread in distance running. Maybe more so in cycling and triathlon, or sprinting but not familiar with the individuals and dynamics/culture of those sports.
Read these threads and you'd think 50% of the top 20 for any given age group at WMMs or bigger road races are doing something illegal. That's probably way off. But you can't expect to have a rational discussion on letsrun.