It studied the effects over a 12 month period. Adult males were to carry a cell phone on their right hip for 11 hours a day. At the end of the study, bone mineral density and bone mineral content were measured using dual-energy x-ray absorptiometry. On the face of it, just using the x-ray machine seems to be one of those cases where simply "observing" the subject can affect the results.
Both bone mineral density and content were lower than in that of non-users. Lower bone mineral density is something we all go through as we age. New bone mass is grown at a slower rate than deterioration occurs. Calcium and other minerals are lost and the bone becomes lighter and more fragile. This study suggests that carrying a cell phone close to your body for extended periods of time each day will hasten this natural loss.
Up until two years ago I constantly carried my phone around in a holster. Now I transport it around in my pockets but put it on the table once I get where I am going. I am not sure why I changed, but this study suggests I did the right thing.
Will you change where you carry your phone if you currently use a holster?