What are you activities, or how have they changed? And any mid-life crisis stories like getting married to someone half your age, hang gliding, taking up motorcycles for the first time, etc? On December 1st of every calendar year, these facts get complied by the Census Bureau in the United States, and this information is useful for a lot of reasons, especially holiday season merchants. Anyway, middle age is where bone mass and muscle mass typically start reducing, egg and sperm count lower, and energy levels decrease. This happens for many starting between age 39-41 and continues at a fairly rapid pace. Or numerically, anybody in the demographic of people born in the boomer years and earlier part of generation X, 1946-1970. You guys and gals born from 1971-early 80s will get there soon. Let's hear your stories.