New York Times published a very thorough article on the complexities of sleep, which deals with one’s prefence, habits, lifestyle, disorders, the mattress industry and a whole other factors. The article is extensive and loaded with facts and stipulations and here are some excerpts:

Furniture Today’s David Perry: “the mattress is not nearly as sexy a part of the equation as drugs or sleep-disorder centers. It just kind of lies there.” For generations many consumers perceived the innerspring beds of the three dominant “S-brands” — Sealy, Serta and Simmons — to be interchangeable. A Gallup poll 10 years ago found that nearly half of Americans didn’t know what brand of mattress they slept on. The industry blamed itself, often ruthlessly.

“The sleep industry has cheapened the mattress,” says Rick Anderson, North American president for Tempur-Pedic. (Tempur-Pedic is the leader in visco-elastic foam, sometimes called “memory foam,” mattresses, made from spongy polyurethane.) Retailers know they are selling a product bought only grudgingly and only once every 12 or 15 years. So they’ve emphasized low prices, shouting about limited-time-only sales that never actually end. “It’s ‘Buy it cheap, buy it now,’ ” Anderson says. “You turn the mattress into a low-priced commodity and, lo and behold, you shouldn’t be surprised when the consumer tells you the mattress isn’t that important.”+

Both Select Comfort and Tempur-Pedic began trying to change that perception when they introduced their beds in the late ’80s and ’90s. As noninnerspring or “alternative bedding” companies, they were burdened with proving that what they had — air and foam respectively — was not only better than the grid of steel springs we’d employed for a century but worth prices as high as $7,000. Unfortunately, the scant published scientific literature on mattresses offered little help. (There had been few real developments since the ’50s, when one of the first studies exploring the effects of different sleep surfaces found that the differences between sleeping on a new mattress and on a piece of plywood with some carpet slung over it were “not large and not always statistically significant.”) So Select Comfort financed its own mattress research and now shows in its marketing how people’s sleep improved on the Sleep Number Bed in labs at Stanford and Duke.

Select Comfort also began using pressure mapping in its stores. Pressure mapping is a digital diagnostic that shows on a computer screen how the mattress is evenly distributing a customer’s weight and conforming around his body. It illustrates “that you’re wearing the mattress versus lying on top of it,” Bils says. Points of high pressure are uncomfortable, the thinking goes. They force a sleeper to shift or roll over, and that movement disturbs sleep. There doesn’t appear to be solid scientific validation of this theory; typical sleepers have been shown to change positions 20 to 60 times a night. But when I mentioned that to Anderson at Tempur-Pedic, which promotes its beds for the same reason, he shot back: “They don’t need to.”

By 2005, noninnerspring beds accounted for nearly a quarter of the

$4.6 billion spent on mattresses. Their staying power and overt sciencey-ness had colossal ripple effects on the entire industry. Jim Gabbert, the second-generation mattress retailer behind Zia Sleep Sanctuary, explains: “At first everyone saw air and visco as a fad, like water beds. ‘It won’t amount to much.’ Now all the mainstream innerspring manufacturers are scrambling to compete with those guys. Those specialty manufacturers taught the mainline brand names that you can price things higher, add more features, have a better story.”