This isn't going to surprise any midlife man (which, coincidentally, just happens to be the name of that great book penned by me, and which makes such a great Christmas, Easter, Passover, Purim, Ramadan, Chinese New Year, and birthday gift), or his partner, but sleep in middle age ain't what it used to be.

Now we've known for many years that sleep deteriorates with age: you sleep fewer hours, you sleep less deeply, you have more trouble falling asleep, you wake more easily, you're more tired during the day, you have less REM (rapid eye movement) sleep, and so on. What is surprising, though, according to a study in the Journal of the American Medical Association, is that some of these changes occur much earlier than we previously thought, and that they are also linked to some other surprising metabolic alterations.

Specifically, this study found that, as expected in men (the study didn't examine women), time spent asleep falls steadily from midlife on (at the rate of about 27 minutes a decade), and REM sleep falls significantly after age 50. This is also accompanied by a corresponding rise in cortisol levels (a hormone associated with stress).

What is more surprising, I think, is that there is also a steep, steady fall in "deep" sleep starting early in young adulthood, and that this decline coincides with a fall in growth hormone levels. Why would that matter, given that by middle age, none of us are growing anymore? Well, that depends on how you define "growing," because nearly all men do grow in midlife, although not vertically. That is, decreased growth hormone levels are associated with lowered muscle mass and increases in fat tissue, especially around the middle, which is why so many midlife men's bellies look like the Astrodome from the side.

Now, although we still don't know which is the cart and which the horse (that is, does the drop in deep sleep lead to a fall in growth hormone, or does the fall in growth hormone lead to less deep sleep), this finding nevertheless leads to the prospect that treating midlife men with growth hormone might not only help them sleep better, it might also help them look better, feel better, and be better proportioned. In fact, studies to determine how this all works are already underway.

To me, though, the more intriguing prospect is that if we could somehow train ourselves to sleep more deeply, then perhaps we midlife guys could also correspondingly increase our growth hormone levels, that is, you could get slimmer just by sleeping more, and, you know, that's one lifestyle change that would be an easy sell to most guys I know.