New research shows that sleep apnea may disrupt the daily process of renewing bone. Read a summary article here. Other studies also show a relationship between lack of sleep, for whatever reason, and lower bone density. Another article gives some tips on getting a better night's sleep.
Here is an article that reports on research to develop a new tool for measuring bone strength rather than bone density. The tool is called an Osteoprobe and measures mechanical properties of bone. So far it is only approved for research, but someday may be used as an alternative to Dexa scans, as a diagnostic tool for osteoporosis and risk of fracture.