You don't "turn into" an elderly person. It's not like you're young and spry one day and then elderly when the clock strikes midnight as you turn 60. If we're talking senior citizen, that's legally defined as 65. If we're talking elderly, that's more an issue of physicality on an individual basis. Some people are old and decrepit at 55, some are still in pretty healthy, great shape at 75. It's different for everyone.