I'm 39 and regularly hit 240 when "sprinting" up the longest hills in east Kent (which can be longish but lets face it not alpine). Its been the same since I really took up cycling 16 years ago,
It could be I'm about to drop dead or have a dicky ticker but my max heart rate hasn't reduced since I was 23 years old . When very fit my lowest rate has got down to 55 and is now back to about 70 (with almost no training).
The only conclusion I've ever reached is that human physiology varies quite a bit.