A new study has found a link between the activity levels of elderly people who have just been released from the hospital and the risk that they will require readmission within 30 days.The investigation draws on data collected from 111 patients aged 65 and older, each of whom was fitted with a "step activity monitor" during his or her hospital stay. Worn on the patient's ankle, the pager-sized device counted every step the person took during hospitalization and for a week after discharge.