Some studies I read note a significant percentage of serious fractures in women with osteopenia. But the study speculated that they were younger and more active women in general since the percentage of compression fractures was higher among women with osteoporosis. So the latter group likely was more risk-averse in general. I mean one can fracture a bone at any age if damaged in sports activity or other common cause. But I think there few absolutes with any of this stuff.

One study I read, and I wish I'd saved it, questioned whether bone density should be such a singular, significant risk when it tells little about overall bone health. The doctors who wrote it noted cases of very strong and resilient bone of, nonetheless, lower density. The suggestion was that some bodies develop stronger though less dense bone. As if bone, in cases of patients with low density, developed a kind of lightweight carbon steel bone as a result. I wouldn't count on it but the human body is still an enigma so who knows what science will know in 50 years?