I'm 6'1", have been that height almost 50 years now. I haven't shrunk in height <yet>. I have noticed my buddies are showing signs of getting a bit shorter. My friends that are still lifting heavy shit (construction, snowmobiles, atvs, other heavy things regularly) do seem to be shrinking.
I've always attributed "shrinking" to compression of the spine, the discs/pads between the vertebra. I drink a lot of milk, always have. About 3g or more a week. Also I've had an office/lab job most all my life, lifting heavy stuff was not part of the job. I still lift some relatively heavy stuff in my daily life but not to the degree of some of my old friends approaching retirement age. I've been cutting/lifting/piling 4' firewood logs this past week. Many of my old friends are definitely shrinking and I've noticed the change in the last few years. I think moderation in lifting heavy weights and drinking lots of milk helps prevent shrinking.
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