Why is restful sleep so much more difficult to achieve as I get older?

Your melatonin production actually peaks when you are very young, around the age of 5, when you could sleep anytime and anywhere. But your melatonin production slowly declines over time, to the point that by age 60, you could have as little as 20% of the melatonin levels you enjoyed in your youth. Plus, many common drugs and over-the-counter medications can further inhibit melatonin synthesis.