Monitoring Osteoporosis Therapy With Bone Densitometry<SUBTITLE>Misleading Changes and Regression to the Mean</SUBTITLE>

Our data suggest that most women who lose BMD during the first year of treatment with alendronate or raloxifene will gain BMD if the same treatment is continued for a second year. These results illustrate the principle of regression to the mean and suggest that effective treatments for osteoporosis should not be changed because of loss of BMD during the first year of use.