Thousands of Medicare beneficiaries will receive an invitation in May to be part of a special study looking at the impact of age-related changes on functional ability. The National Health and Aging Trends Study (NHATS) will be seeking some 9,000 people aged 65 and older to participate in this long-term study, funded by the National Institute on Aging (NIA), part of the National Institutes of Health. NHATS will examine how the daily lives of older adults change as they age. Participants will be randomly chosen from across the country.