Technically, insomnia is defined as either not being able to get to sleep in the first place or not being able to get back to sleep after waking up.People over the age of 65 wake up 25 times per night, on average, and that number increases with age. One-third of people wake up repeatedly during the night, while 25 percent wake up early in the morning and can’t get back to sleep.The big problem for most of you is an increase in sleep latency (how long it takes to fall asleep), as you worry about work, money or whatever else is on your mind.The likely chemical culprit in insomnia is melatonin. Normally, melatonin levels rise about two hours before bedtime and peak when your body temperature is the lowest, to help induce sleep. But without adequate melatonin, your body is unable to transition from sleep latency to sleep stage 1.QUIZ: Do You Have Good Sleep Habits?